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7dce7109-6077-4603-8837-cc3e920a8583 | 7dce7109-6077-4603-8837-cc3e920a8583 | 7dce7109-6077-4603-8837-cc3e920a8583 | human | null | null | none | abstracts | Nonstationary pattern in unsynchronizable complex networks | null | Pattern formation and evolution in unsynchronizable complex networks are investigated. Due to the asymmetric topology, the synchronous patterns formed in complex networks are irregular and nonstationary. For coupling strength immediately out of the synchronizable region, the typical phenomenon is the on-off intermittency of the system dynamics. The patterns appeared in this process are signatured by the coexistence of a giant cluster, which comprises most of the nodes, and a few number of small clusters. The pattern evolution is characterized by the giant cluster irregularly absorbs or emits the small clusters. As the coupling strength leaves away from the synchronization bifurcation point, the giant cluster is gradually dissolved into a number of small clusters, and the system dynamics is characterized by the integration and separation of the small clusters. Dynamical mechanisms and statistical properties of the nonstationary pattern evolution are analyzed and conducted, and some sc |
1aa9fa9f-a80e-46f6-8daf-6a5e84a28f21 | 1aa9fa9f-a80e-46f6-8daf-6a5e84a28f21 | 1aa9fa9f-a80e-46f6-8daf-6a5e84a28f21 | human | null | null | none | abstracts | The Solar Neighborhood. XIX. Discovery and Characterization of 33 New
Nearby White Dwarf Systems | null | We present spectra for 33 previously unclassified white dwarf systems brighter than V = 17 primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We suspect three of these systems are unresolved double degenerates. We obtained VRI photometry for these 33 objects as well as for 23 known white dwarf systems without trigonometric parallaxes, also primarily in the southern hemisphere. For the 56 objects, we converted the photometry values to fluxes and fit them to a spectral energy distribution using the spectroscopy to determine which model to use (i.e. pure hydrogen, pure helium, or metal-rich helium), resulting in estimates of effective temperature and distance. Eight of the new and 12 known systems are estimated to be within the NStars and Catalogue of Nearby Stars (CNS) horizons of 25 pc, constituting a potential 18% increase in the nearby white dwarf sample. Trigonometric parallax determinations are underway via CTIOPI for these 20 s |
57d4b2ea-1f8f-4cd8-afb6-d993093268d3 | 57d4b2ea-1f8f-4cd8-afb6-d993093268d3 | 57d4b2ea-1f8f-4cd8-afb6-d993093268d3 | human | null | null | none | abstracts | New possible properties of atomic nuclei investigated by non linear
methods: Fractal and recurrence quantification analysis | null | For the first time we apply the methodologies of nonlinear analysis to investigate atomic matter. We use these methods in the analysis of Atomic Weights and of Mass Number of atomic nuclei. Using the AutoCorrelation Function and Mutual Information we establish the presence of nonlinear effects in the mechanism of increasing mass of atomic nuclei considered as a function of the atomic number. We find that increasing mass is divergent, possibly chaotic. We also investigate the possible existence of a Power Law for atomic nuclei and, using also the technique of the variogram, we conclude that a fractal regime could superintend to the mechanism of increasing mass for nuclei. Finally, using the Hurst exponent, evidence is obtained that the mechanism of increasing mass in atomic nuclei is in the fractional Brownian regime. The most interesting results are obtained by using Recurrence Quantification Analysis (RQA). New recurrences, psudoperiodicities, self-resemblance and class of self-simi |
db056972-86cd-435a-bd90-4ad2b8a126c5 | db056972-86cd-435a-bd90-4ad2b8a126c5 | db056972-86cd-435a-bd90-4ad2b8a126c5 | human | null | null | none | abstracts | Extragalactic Radio Sources and the WMAP Cold Spot | null | We detect a dip of 20-45% in the surface brightness and number counts of NVSS sources smoothed to a few degrees at the location of the WMAP cold spot. The dip has structure on scales of approximately 1-10 degrees. Together with independent all-sky wavelet analyses, our results suggest that the dip in extragalactic brightness and number counts and the WMAP cold spot are physically related, i.e., that the coincidence is neither a statistical anomaly nor a WMAP foreground correction problem. If the cold spot does originate from structures at modest redshifts, as we suggest, then there is no remaining need for non-Gaussian processes at the last scattering surface of the CMB to explain the cold spot. The late integrated Sachs-Wolfe effect, already seen statistically for NVSS source counts, can now be seen to operate on a single region. To create the magnitude and angular size of the WMAP cold spot requires a ~140 Mpc radius completely empty void at z<=1 along this line of sight. This is f |
8e8ef6d6-e20f-417a-9550-cd8c3e0cb50b | 8e8ef6d6-e20f-417a-9550-cd8c3e0cb50b | 8e8ef6d6-e20f-417a-9550-cd8c3e0cb50b | human | null | null | none | abstracts | Smooth and Starburst Tidal Tails in the GEMS and GOODS Fields | null | GEMS and GOODS fields were examined to z~1.4 for galaxy interactions and mergers. The basic morphologies are familiar: antennae with long tidal tails, tidal dwarfs, and merged cores; M51-type galaxies with disk spirals and tidal arm companions; early-type galaxies with diffuse plumes; equal-mass grazing-collisions; and thick J-shaped tails beaded with star formation and double cores. One type is not common locally and is apparently a loose assemblage of smaller galaxies. Photometric measurements were made of the tails and clumps, and physical sizes were determined assuming photometric redshifts. Antennae tails are a factor of ~3 smaller in GEMS and GOODS systems compared to local antennae; their disks are a factor of ~2 smaller than locally. Collisions among early type galaxies generally show no fine structure in their tails, indicating that stellar debris is usually not unstable. One exception has a 5x10**9 Msun smooth red clump that could be a pure stellar condensation. Most tidal |
ee5dd676-3bfb-408b-8dc0-8c47e4104b64 | ee5dd676-3bfb-408b-8dc0-8c47e4104b64 | ee5dd676-3bfb-408b-8dc0-8c47e4104b64 | human | null | null | none | abstracts | Domain wall switching: optimizing the energy landscape | null | It has recently been suggested that exchange spring media offer a way to increase media density without causing thermal instability (superparamagnetism), by using a hard and a soft layer coupled by exchange. Victora has suggested a figure of merit xi = 2 E_b/mu_0 m_s H_sw, the ratio of the energy barrier to that of a Stoner-Wohlfarth system with the same switching field, which is 1 for a Stoner-Wohlfarth (coherently switching) particle and 2 for an optimal two-layer composite medium. A number of theoretical approaches have been used for this problem (e.g., various numbers of coupled Stoner-Wohlfarth layers and continuum micromagnetics). In this paper we show that many of these approaches can be regarded as special cases or approximations to a variational formulation of the problem, in which the energy is minimized for fixed magnetization. The results can be easily visualized in terms of a plot of the energy as a function of magnetic moment m_z, in which both the switching field [the |
27e6679d-d2d4-4389-92a0-4703606b4ac0 | 27e6679d-d2d4-4389-92a0-4703606b4ac0 | 27e6679d-d2d4-4389-92a0-4703606b4ac0 | human | null | null | none | abstracts | The HARPS search for southern extra-solar planets. IX. Exoplanets
orbiting HD 100777, HD 190647, and HD 221287 | null | The HARPS high-resolution high-accuracy spectrograph is offered to the astronomical community since the second half of 2003. Since then, we have been using this instrument for monitoring radial velocities of a large sample of Solar-type stars (~1400 stars) in order to search for their possible low-mass companions. Amongst the goals of our survey, one is to significantly increase the number of detected extra-solar planets in a volume-limited sample to improve our knowledge of their orbital elements distributions and thus obtain better constraints for planet-formation models. In this paper, we present the HARPS radial-velocity data and orbital solutions for 3 Solar-type stars: HD 100777, HD 190647, and HD 221287. The radial-velocity data of HD 100777 is best explained by the presence of a 1.1 M_Jup planetary companion on a 384--day eccentric orbit (e=0.36). The orbital fit obtained for the slightly evolved star HD 190647 reveals the presence of a long-period (P=1038 d) 1.9 M_Jup plan |
47a2e27a-3686-4554-9a3d-951f45ff911c | 47a2e27a-3686-4554-9a3d-951f45ff911c | 47a2e27a-3686-4554-9a3d-951f45ff911c | human | null | null | none | abstracts | Interactions, superconducting $T_c$, and fluctuation magnetization for
two coupled dots in the crossover between the Gaussian Orthogonal and Unitary
ensembles | null | We study a system of two quantum dots connected by a hopping bridge. Both the dots and connecting region are assumed to be in universal crossover regimes between Gaussian Orthogonal and Unitary ensembles. Using a diagrammatic approach appropriate for energy separations much larger than the level spacing we obtain the ensemble-averaged one- and two-particle Green's functions. It turns out that the diffuson and cooperon parts of the two-particle Green's function can be described by separate scaling functions. We then use this information to investigate a model interacting system in which one dot has an attractive s-wave reduced Bardeen-Cooper-Schrieffer interaction, while the other is noninteracting but subject to an orbital magnetic field. We find that the critical temperature is {\it nonmonotonic} in the flux through the second dot in a certain regime of interdot coupling. Likewise, the fluctuation magnetization above the critical temperature is also nonmonotonic in this regime, can |
28c62904-3666-4e71-a999-088c0c83c96e | 28c62904-3666-4e71-a999-088c0c83c96e | 28c62904-3666-4e71-a999-088c0c83c96e | human | null | null | none | abstracts | Z^0 \to 2\gamma and the Twisted Coproduct of the Poincar\'{e} Group | null | Yang's theorem forbids the process $Z^0 \to 2\gamma$ in any Poincar\'{e} invariant theory if photons are bosons and their two-particle states transform under the Poincar\'{e} group in the standard way (under the standard coproduct of the Poincar\'{e} group). This is an important result as it does not depend on the assumptions of quantum field theory. Recent work on noncommutative geometry requires deforming the above coproduct by the Drinfel'd twist. We prove that $Z^0 \to 2\gamma$ is forbidden for the twisted coproduct as well. This result is also independent of the assumptions of quantum field theory. As an illustration of the use of our general formulae, we further show that $Z^0 \to \nu + \nu$ is forbidden for the standard or twisted coproduct of the Poincar\'{e} group if the neutrino is massless, even if lepton number is not conserved. This is a special case of our general result that a massive particle of spin $j$ cannot decay into two identical massless particles of the same h |
9f0d24c9-cb35-4f61-980c-1e8501ee8044 | 9f0d24c9-cb35-4f61-980c-1e8501ee8044 | 9f0d24c9-cb35-4f61-980c-1e8501ee8044 | human | null | null | none | abstracts | A Symplectic Test of the L-Functions Ratios Conjecture | null | Recently Conrey, Farmer and Zirnbauer conjectured formulas for the averages over a family of ratios of products of shifted L-functions. Their L-functions Ratios Conjecture predicts both the main and lower order terms for many problems, ranging from n-level correlations and densities to mollifiers and moments to vanishing at the central point. There are now many results showing agreement between the main terms of number theory and random matrix theory; however, there are very few families where the lower order terms are known. These terms often depend on subtle arithmetic properties of the family, and provide a way to break the universality of behavior. The L-functions Ratios Conjecture provides a powerful and tractable way to predict these terms. We test a specific case here, that of the 1-level density for the symplectic family of quadratic Dirichlet characters arising from even fundamental discriminants d \le X. For test functions supported in (-1/3, 1/3) we calculate all the lower |
b36d9931-b482-4030-85df-fc09ca29d351 | b36d9931-b482-4030-85df-fc09ca29d351 | b36d9931-b482-4030-85df-fc09ca29d351 | human | null | null | none | abstracts | Cosmology from String Theory | null | We explore the cosmological content of Salam-Sezgin six dimensional supergravity, and find a solution to the field equations in qualitative agreement with observation of distant supernovae, primordial nucleosynthesis abundances, and recent measurements of the cosmic microwave background. The carrier of the acceleration in the present de Sitter epoch is a quintessence field slowly rolling down its exponential potential. Intrinsic to this model is a second modulus which is automatically stabilized and acts as a source of cold dark matter with a mass proportional to an exponential function of the quintessence field (hence realizing VAMP models within a String context). However, any attempt to saturate the present cold dark matter component in this manner leads to unacceptable deviations from cosmological data -- a numerical study reveals that this source can account for up to about 7% of the total cold dark matter budget. We also show that (1) the model will support a de Sitter energy i |
99c4909e-34f8-4734-b715-f3d788a580cd | 99c4909e-34f8-4734-b715-f3d788a580cd | 99c4909e-34f8-4734-b715-f3d788a580cd | human | null | null | none | abstracts | The Isophotal Structure of Early-Type Galaxies in the SDSS: Dependence
on AGN Activity and Environment | null | We study the dependence of the isophotal shape of early-type galaxies on their absolute B-band magnitude, their dynamical mass, and their nuclear activity and environment, using an unprecedented large sample of 847 early-type galaxies identified in the SDSS by Hao et al (2006). We find that the fraction of disky galaxies smoothly decreases with increasing luminosity. The large sample allows us to describe these trends accurately with tight linear relations that are statistically robust against the uncertainty in the isophotal shape measurements. There is also a host of significant correlations between the disky fraction and indicators of nuclear activity (both in the optical and in the radio) and environment (soft X-rays, group mass, group hierarchy). Our analysis shows however that these correlations can be accurately matched by assuming that the disky fraction depends only on galaxy luminosity or mass. We therefore conclude that neither the level of activity, nor group mass or grou |
983d6e33-c292-41dc-a041-5ae29f326c39 | 983d6e33-c292-41dc-a041-5ae29f326c39 | 983d6e33-c292-41dc-a041-5ae29f326c39 | human | null | null | none | abstracts | Recovering galaxy star formation and metallicity histories from spectra
using VESPA | null | We introduce VErsatile SPectral Analysis (VESPA): a new method which aims to recover robust star formation and metallicity histories from galactic spectra. VESPA uses the full spectral range to construct a galaxy history from synthetic models. We investigate the use of an adaptative parametrization grid to recover reliable star formation histories on a galaxy-by-galaxy basis. Our goal is robustness as opposed to high resolution histories, and the method is designed to return high time resolution only where the data demand it. In this paper we detail the method and we present our findings when we apply VESPA to synthetic and real Sloan Digital Sky Survey (SDSS) spectroscopic data. We show that the number of parameters that can be recovered from a spectrum depends strongly on the signal-to-noise, wavelength coverage and presence or absence of a young population. For a typical SDSS sample of galaxies, we can normally recover between 2 to 5 stellar populations. We find very good agreemen |
2e248860-eee7-4ae1-8b39-02a12b66264c | 2e248860-eee7-4ae1-8b39-02a12b66264c | 2e248860-eee7-4ae1-8b39-02a12b66264c | human | null | null | none | abstracts | Search for gravitational-wave bursts in LIGO data from the fourth
science run | null | The fourth science run of the LIGO and GEO 600 gravitational-wave detectors, carried out in early 2005, collected data with significantly lower noise than previous science runs. We report on a search for short-duration gravitational-wave bursts with arbitrary waveform in the 64-1600 Hz frequency range appearing in all three LIGO interferometers. Signal consistency tests, data quality cuts, and auxiliary-channel vetoes are applied to reduce the rate of spurious triggers. No gravitational-wave signals are detected in 15.5 days of live observation time; we set a frequentist upper limit of 0.15 per day (at 90% confidence level) on the rate of bursts with large enough amplitudes to be detected reliably. The amplitude sensitivity of the search, characterized using Monte Carlo simulations, is several times better than that of previous searches. We also provide rough estimates of the distances at which representative supernova and binary black hole merger signals could be detected with 50% e |
a0b2de8e-eab1-43e8-810f-62785f143304 | a0b2de8e-eab1-43e8-810f-62785f143304 | a0b2de8e-eab1-43e8-810f-62785f143304 | human | null | null | none | abstracts | Spectroscopy of Nine Cataclysmic Variable Stars | null | We present optical spectroscopy of nine cataclysmic binary stars, mostly dwarf novae, obtained primarily to determine orbital periods Porb. The stars and their periods are LX And, 0.1509743(5) d; CZ Aql, 0.2005(6) d; LU Cam, 0.1499686(4) d; GZ Cnc, 0.0881(4) d; V632 Cyg, 0.06377(8) d; V1006 Cyg, 0.09903(9) d; BF Eri, 0.2708804(4) d; BI Ori, 0.1915(5) d; and FO Per, for which Porb is either 0.1467(4) or 0.1719(5) d. Several of the stars proved to be especially interesting. In BF Eri, we detect the absorption spectrum of a secondary star of spectral type K3 +- 1 subclass, which leads to a distance estimate of approximately 1 kpc. However, BF Eri has a large proper motion (100 mas/yr), and we have a preliminary parallax measurement that confirms the large proper motion and yields only an upper limit for the parallax. BF Eri's space velocity is evidently large, and it appears to belong to the halo population. In CZ Aql, the emission lines have strong wings that move with large velocity |
2e666ce0-d6d9-4870-9892-2d48c79545a7 | 2e666ce0-d6d9-4870-9892-2d48c79545a7 | 2e666ce0-d6d9-4870-9892-2d48c79545a7 | human | null | null | none | abstracts | Displacement of the Sun from the Galactic Plane | null | We have carried out a comparative statistical study for the displacement of the Sun from the Galactic plane (z_\odot) following three different methods. The study has been done using a sample of 537 young open clusters (YOCs) with log(Age) < 8.5 lying within a heliocentric distance of 4 kpc and 2030 OB stars observed up to a distance of 1200 pc, all of them have distance information. We decompose the Gould Belt's member in a statistical sense before investigating the variation in the z_\odot estimation with different upper cut-off limits in the heliocentric distance and distance perpendicular to the Galactic plane. We found z_\odot varies in a range of ~ 13 - 20 pc from the analys is of YOCs and ~ 6 - 18 pc from the OB stars. A significant scatter in the z_\odot obtained due to different cut-off values is noticed for the OB stars although no such deviation is seen for the YOCs. We also determined scale heights of 56.9(+3.8)(-3.4} and 61.4(+2.7)(-2.4) pc for the distribution of YOCs a |
a6621755-5a92-43f3-afe7-60bc7b182968 | a6621755-5a92-43f3-afe7-60bc7b182968 | a6621755-5a92-43f3-afe7-60bc7b182968 | human | null | null | none | abstracts | Correlation amplitude and entanglement entropy in random spin chains | null | Using strong-disorder renormalization group, numerical exact diagonalization, and quantum Monte Carlo methods, we revisit the random antiferromagnetic XXZ spin-1/2 chain focusing on the long-length and ground-state behavior of the average time-independent spin-spin correlation function C(l)=\upsilon l^{-\eta}. In addition to the well-known universal (disorder-independent) power-law exponent \eta=2, we find interesting universal features displayed by the prefactor \upsilon=\upsilon_o/3, if l is odd, and \upsilon=\upsilon_e/3, otherwise. Although \upsilon_o and \upsilon_e are nonuniversal (disorder dependent) and distinct in magnitude, the combination \upsilon_o + \upsilon_e = -1/4 is universal if C is computed along the symmetric (longitudinal) axis. The origin of the nonuniversalities of the prefactors is discussed in the renormalization-group framework where a solvable toy model is considered. Moreover, we relate the average correlation function with the average entanglement entropy |
798b66e9-488a-4322-a4c1-925889ef3659 | 798b66e9-488a-4322-a4c1-925889ef3659 | 798b66e9-488a-4322-a4c1-925889ef3659 | human | null | null | none | abstracts | SIM PlanetQuest: The Most Promising Near-Term Technique to Detect, Find
Masses, and Determine Three-Dimensional Orbits of Nearby Habitable Planets | null | The past two Decadal Surveys in Astronomy and Astrophysics recommended the completion of a space-based interferometry mission, known today as SIM PlanetQuest, for its unique ability to detect and characterize nearby rocky planets (Bahcall 1991, McKee & Taylor 2001), as well as contributions to a broad range of problems in astrophysics. Numerous committees of the National Research Council as well as NASA Roadmaps have similarly highlighted SIM as the one technology that offers detection and characterization of rocky planets around nearby stars and which is technically ready. To date, SIM remains the only program with the capability of detecting and confirming rocky planets in the habitable zones of nearby solar-type stars. Moreover, SIM measures masses and three-dimensional orbits of habitable planets around nearby stars (within 25 pc); these are the only stars for which follow-up by other techniques is feasible, such as space-based spectroscopy, ground-based interferometry, and of co |
0b000c89-9ab5-4747-a4cb-6c71aaca9416 | 0b000c89-9ab5-4747-a4cb-6c71aaca9416 | 0b000c89-9ab5-4747-a4cb-6c71aaca9416 | human | null | null | none | abstracts | IR observations of MS 1054-03: Star Formation and its Evolution in Rich
Galaxy Clusters | null | We study the infrared (IR) properties of galaxies in the cluster MS 1054-03 at z=0.83 by combining MIPS 24 micron data with spectra of more than 400 galaxies and a very deep K-band selected catalog. 19 IR cluster members are selected spectroscopically, and an additional 15 are selected by their photometric redshifts. We derive the IR luminosity function of the cluster and find strong evolution compared to the similar-mass Coma cluster. The best fitting Schechter function gives L*_{IR}=11.49 +0.30/-0.29 L_sun with a fixed faint end slope, about one order of magnitude larger than that in Coma. The rate of evolution of the IR luminosity from Coma to MS 1054-03 is consistent with that found in field galaxies, and it suggests that some internal mechanism, e.g., the consumption of the gas fuel, is responsible for the general decline of the cosmic star formation rate (SFR) in different environments. The mass-normalized integrated SFR within 0.5R_200 in MS 1054-03 also shows evolution compar |
7688cd06-d707-4388-a109-30b28abe2a1e | 7688cd06-d707-4388-a109-30b28abe2a1e | 7688cd06-d707-4388-a109-30b28abe2a1e | human | null | null | none | abstracts | On the orbital period of the magnetic Cataclysmic Variable HS 0922+1333 | null | Context: The object HS 0922+1333 was visited briefly in 2002 in a mini survey of low accretion rate polars (LARPs) in order to test if they undergo high luminosity states similar to ordinary polars. On the basis of that short observation the suspicion arose that the object might be an asynchronous polar (Tovmassian et al. 2004). The disparity between the presumed orbital and spin period appeared to be quite unusual. Aims: We performed follow-up observations of the object to resolve the problem. Methods: New simultaneous spectroscopic and photometric observations spanning several years allowed measurements of radial velocities of emission and absorption lines from the secondary star and brightness variations due to synchrotron emission from the primary. Results: New observations show that the object is actually synchronous and its orbital and spin period are equal to 4.04 hours. Conclusions: We identify the source of confusion of previous observations to be a high velocity component o |
4118ea7e-d99b-4555-bfca-d2b63105db9b | 4118ea7e-d99b-4555-bfca-d2b63105db9b | 4118ea7e-d99b-4555-bfca-d2b63105db9b | human | null | null | none | abstracts | Nova Geminorum 1912 and the Origin of the Idea of Gravitational Lensing | null | Einstein's early calculations of gravitational lensing, contained in a scratch notebook and dated to the spring of 1912, are reexamined. A hitherto unknown letter by Einstein suggests that he entertained the idea of explaining the phenomenon of new stars by gravitational lensing in the fall of 1915 much more seriously than was previously assumed. A reexamination of the relevant calculations by Einstein shows that, indeed, at least some of them most likely date from early October 1915. But in support of earlier historical interpretation of Einstein's notes, it is argued that the appearance of Nova Geminorum 1912 (DN Gem) in March 1912 may, in fact, provide a relevant context and motivation for Einstein's lensing calculations on the occasion of his first meeting with Erwin Freundlich during a visit in Berlin in April 1912. We also comment on the significance of Einstein's consideration of gravitational lensing in the fall of 1915 for the reconstruction of Einstein's final steps in his |
1c3d632d-f38d-4ff2-9543-9e4935a10030 | 1c3d632d-f38d-4ff2-9543-9e4935a10030 | 1c3d632d-f38d-4ff2-9543-9e4935a10030 | human | null | null | none | abstracts | Cross-Layer Optimization of MIMO-Based Mesh Networks with Gaussian
Vector Broadcast Channels | null | MIMO technology is one of the most significant advances in the past decade to increase channel capacity and has a great potential to improve network capacity for mesh networks. In a MIMO-based mesh network, the links outgoing from each node sharing the common communication spectrum can be modeled as a Gaussian vector broadcast channel. Recently, researchers showed that ``dirty paper coding'' (DPC) is the optimal transmission strategy for Gaussian vector broadcast channels. So far, there has been little study on how this fundamental result will impact the cross-layer design for MIMO-based mesh networks. To fill this gap, we consider the problem of jointly optimizing DPC power allocation in the link layer at each node and multihop/multipath routing in a MIMO-based mesh networks. It turns out that this optimization problem is a very challenging non-convex problem. To address this difficulty, we transform the original problem to an equivalent problem by exploiting the channel duality. Fo |
0bdd5d62-6ec3-4ff3-9748-8e99acff89d4 | 0bdd5d62-6ec3-4ff3-9748-8e99acff89d4 | 0bdd5d62-6ec3-4ff3-9748-8e99acff89d4 | human | null | null | none | abstracts | X-ray Timing Observations of PSR J1930+1852 in the Crab-like SNR
G54.1+0.3 | null | We present new X-ray timing and spectral observations of PSR J1930+1852, the young energetic pulsar at the center of the non-thermal supernova remnant G54.1+0.3. Using data obtained with the Rossi X-ray Timing Explorer and Chandra X-ray observatories we have derived an updated timing ephemeris of the 136 ms pulsar spanning 6 years. During this interval, however, the period evolution shows significant variability from the best fit constant spin-down rate of $\dot P = 7.5112(6) \times 10^{-13}$ s s$^{-1}$, suggesting strong timing noise and/or glitch activity. The X-ray emission is highly pulsed ($71\pm5%$ modulation) and is characterized by an asymmetric, broad profile ($\sim 70%$ duty cycle) which is nearly twice the radio width. The spectrum of the pulsed emission is well fitted with an absorbed power law of photon index $\Gamma = 1.2\pm0.2$; this is marginally harder than that of the unpulsed component. The total 2-10 keV flux of the pulsar is $1.7 \times 10^{-12}$ erg cm$^{-2}$ s$ |
8c248a04-dd3e-42bd-9218-b9a24ca16e09 | 8c248a04-dd3e-42bd-9218-b9a24ca16e09 | 8c248a04-dd3e-42bd-9218-b9a24ca16e09 | human | null | null | none | abstracts | Distribution of the molecular absorption in front of the quasar
B0218+357 | null | The line of sight to the quasar B0218+357, one of the most studied lensed systems, intercepts a z=0.68 spiral galaxy, which splits its image into two main components A and B, separated by ca. 0.3'', and gives rise to molecular absorption. Although the main absorption component has been shown to arise in front of image A, it is not established whether some absorption from other velocity components is also occuring in front of image B. To tackle this question, we have observed the HCO+(2-1) absorption line during the commissioning phase of the new very extended configuration of the Plateau de Bure Interferometer, in order to trace the position of the absorption as a function of frequency. Visibility fitting of the self-calibrated data allowed us to achieve position accuracy between ~12 and 80 mas per velocity component. Our results clearly demonstrate that all the different velocity components of the HCO+(2-1) absorption arise in front of the south-west image A of the quasar. We estima |
81597f90-e8c6-4625-981f-051095804a8e | 81597f90-e8c6-4625-981f-051095804a8e | 81597f90-e8c6-4625-981f-051095804a8e | human | null | null | none | abstracts | Daemons and DAMA: Their Celestial-Mechanics Interrelations | null | The assumption of the capture by the Solar System of the electrically charged Planckian DM objects (daemons) from the galactic disk is confirmed not only by the St.Petersburg (SPb) experiments detecting particles with V<30 km/s. Here the daemon approach is analyzed considering the positive model independent result of the DAMA/NaI experiment. We explain the maximum in DAMA signals observed in the May-June period to be associated with the formation behind the Sun of a trail of daemons that the Sun captures into elongated orbits as it moves to the apex. The range of significant 2-6-keV DAMA signals fits well the iodine nuclei elastically knocked out of the NaI(Tl) scintillator by particles falling on the Earth with V=30-50 km/s from strongly elongated heliocentric orbits. The half-year periodicity of the slower daemons observed in SPb originates from the transfer of particles that are deflected through ~90 deg into near-Earth orbits each time the particles cross the outer reaches of the |
8033f19b-2773-4e5e-87cf-50099d46901d | 8033f19b-2773-4e5e-87cf-50099d46901d | 8033f19b-2773-4e5e-87cf-50099d46901d | human | null | null | none | abstracts | A kind of prediction from string phenomenology: extra matter at low
energy | null | We review the possibility that the Supersymmetric Standard Model arises from orbifold constructions of the E_8 x E_8 Heterotic Superstring, and the phenomenological properties that such a model should have. In particular, trying to solve the discrepancy between the unification scale predicted by the Heterotic Superstring (g_{GUT}x5.27x10^{17} GeV) and the value deduced from LEP experiments (2x10^{16} GeV), we will predict the presence at low energies of three families of Higgses and vector-like colour triplets. Our approach relies on the Fayet-Iliopoulos breaking, and this is also a crucial ingredient, together with having three Higgs families, to obtain in these models an interesting pattern of fermion masses and mixing angles at the renormalizable lebel. Namely, after the gauge breaking some physical particles appear combined with other states, and the Yukawa couplings are modified in a well controlled way. On the other hand, dangerous flavour-changing neutral currents may appear w |
57f30c79-1f7c-47c5-851a-9e05e44d4acc | 57f30c79-1f7c-47c5-851a-9e05e44d4acc | 57f30c79-1f7c-47c5-851a-9e05e44d4acc | human | null | null | none | abstracts | Dynamics of Size-Selected Gold Nanoparticles Studied by Ultrafast
Electron Nanocrystallography | null | We report the studies of ultrafast electron nanocrystallography on size-selected Au nanoparticles (2-20 nm) supported on a molecular interface. Reversible surface melting, melting, and recrystallization were investigated with dynamical full-profile radial distribution functions determined with sub-picosecond and picometer accuracies. In an ultrafast photoinduced melting, the nanoparticles are driven to a non-equilibrium transformation, characterized by the initial lattice deformations, nonequilibrium electron-phonon coupling, and upon melting, the collective bonding and debonding, transforming nanocrystals into shelled nanoliquids. The displasive structural excitation at premelting and the coherent transformation with crystal/liquid coexistence during photomelting differ from the reciprocal behavior of recrystallization, where a hot lattice forms from liquid and then thermally contracts. The degree of structural change and the thermodynamics of melting are found to depend on the size |
51998be9-8dd8-45b6-ad29-fc6ab300ab6c | 51998be9-8dd8-45b6-ad29-fc6ab300ab6c | 51998be9-8dd8-45b6-ad29-fc6ab300ab6c | human | null | null | none | abstracts | SBF: multi-wavelength data and models | null | Recent applications have proved that the Surface Brightness Fluctuations (SBF) technique is a reliable distance indicator in a wide range of distances, and a promising tool to analyze the physical and chemical properties of unresolved stellar systems, in terms of their metallicity and age. We present the preliminary results of a project aimed at studying the evolutionary properties and distance of the stellar populations in external galaxies based on the SBF method. On the observational side, we have succeeded in detecting I-band SBF gradients in six bright ellipticals imaged with the ACS, for these same objects we are now presenting also B-band SBF data. These B-band data are the first fluctuations magnitude measurements for galaxies beyond 10 Mpc. To analyze the properties of stellar populations from the data, accurate SBF models are essential. As a part of this project, we have evaluated SBF magnitudes from Simple Stellar Population (SSP) models specifically optimized for the |
c9eb8e38-07d4-40f0-bc2d-daf351e63621 | c9eb8e38-07d4-40f0-bc2d-daf351e63621 | c9eb8e38-07d4-40f0-bc2d-daf351e63621 | human | null | null | none | abstracts | Unstable and Stable Galaxy Models | null | To determine the stability and instability of a given steady galaxy configuration is one of the fundamental problems in the Vlasov theory for galaxy dynamics. In this article, we study the stability of isotropic spherical symmetric galaxy models $f_{0}(E)$, for which the distribution function $f_{0}$ depends on the particle energy $E$ only. In the first part of the article, we derive the first sufficient criterion for linear instability of $f_{0}(E):$ $f_{0}(E)$ is linearly unstable if the second-order operator \[ A_{0}\equiv-\Delta+4\pi\int f_{0}^{\prime}(E)\{I-\mathcal{P}\}dv \] has a negative direction, where $\mathcal{P}$ is the projection onto the function space $\{g(E,L)\},$ $L$ being the angular momentum [see the explicit formula (\ref{A0-radial})]. In the second part of the article, we prove that for the important King model, the corresponding $A_{0}$ is positive definite. Such a positivity leads to the nonlinear stability of the King model under all spherically symmetric per |
096fa0e1-6c99-4e81-8298-5d2c9c111ebc | 096fa0e1-6c99-4e81-8298-5d2c9c111ebc | 096fa0e1-6c99-4e81-8298-5d2c9c111ebc | human | null | null | none | abstracts | Phenomenological theory of spin excitations in La- and Y-based cuprates | null | Motivated by recent inelastic neutron scattering (INS) experiments on La-based cuprates and based on the fermiology theories, we study the spin susceptibility for La-based (e.g., La$_{2-x}$Sr$_x$CuO$_4$) and Y-based (e.g., YBa$_2$Cu$_3$O$_y$) cuprates, respectively. The spin excitation in YBa$_2$Cu$_3$O$_y$ is dominated by a sharp resonance peak at the frequency 40 meV in the superconducting state. Below and above the resonance frequency, the incommensurate (IC) peaks develop and the intensity of the peaks decreases dramatically. In the normal state, the resonant excitation does not occur and the IC peaks are merged into commensurate ones. The spin excitation of La$_{2-x}$Sr$_x$CuO$_4$ is significantly different from that of Y-based ones, namely, the resonance peak does not exist due to the decreasing of the superconducting gap and the presence of the possible spin-stripe order. The spectra are only enhanced at the expected resonance frequency (about 18 meV) while it is still incomme |
111b4c83-3774-4d39-957b-8591b776686a | 111b4c83-3774-4d39-957b-8591b776686a | 111b4c83-3774-4d39-957b-8591b776686a | human | null | null | none | abstracts | Environmental dielectric screening effect on exciton transition energies
in single-walled carbon nanotubes | null | Environmental dielectric screening effects on exciton transition energies in single-walled carbon nanotubes (SWNTs) have been studied quantitatively in the range of dielectric constants from 1.0 to 37 by immersing SWNTs bridged over trenches in various organic solvents by means of photoluminescence and the excitation spectroscopies. With increasing environmental dielectric constant ($\epsilon_{\rm env}$), both $E_{11}$ and $E_{22}$ exhibited a redshift by several tens meV and a tendency to saturate at a $\epsilon_{\rm env} \sim 5$ without an indication of significant ($n$,$m$) dependence. The redshifts can be explained by dielectric screening of the repulsive electron-electron interaction. The $\epsilon_{\rm env}$ dependence of $E_{11}$ and $E_{22}$ can be expressed by a simple empirical equation with a power law in $\epsilon_{\rm env}$, $E_{\rm ii} = E_{\rm ii}^{\infty} + A\epsilon_{\rm env}^{-\alpha}$. We also immersed a sample in sodium-dodecyl-sulfate (SDS) solution to investigat |
8aad7dbe-25ba-4175-90d9-9d74e8ea93dc | 8aad7dbe-25ba-4175-90d9-9d74e8ea93dc | 8aad7dbe-25ba-4175-90d9-9d74e8ea93dc | human | null | null | none | abstracts | Determination of Low-Energy Parameters of Neutron--Proton Scattering on
the Basis of Modern Experimental Data from Partial-Wave Analyses | null | The triplet and singlet low-energy parameters in the effective-range expansion for neutron--proton scattering are determined by using the latest experimental data on respective phase shifts from the SAID nucleon--nucleon database. The results differ markedly from the analogous parameters obtained on the basis of the phase shifts of the Nijmegen group and contradict the parameter values that are presently used as experimental ones. The values found with the aid of the phase shifts from the SAID nucleon--nucleon database for the total cross section for the scattering of zero-energy neutrons by protons, $\sigma_{0}=20.426 $b, and the neutron--proton coherent scattering length, $f=-3.755 $fm, agree perfectly with the experimental cross-section values obtained by Houk, $\sigma_{0}=20.436\pm 0.023 $b, and experimental scattering-length values obtained by Houk and Wilson, $f=-3.756\pm 0.009 $fm, but they contradict cross-section values of $\sigma_{0}=20.491\pm 0.014 $b according to Dilg and |
df00fff4-9459-4377-b885-cdc67b361ef6 | df00fff4-9459-4377-b885-cdc67b361ef6 | df00fff4-9459-4377-b885-cdc67b361ef6 | human | null | null | none | abstracts | Controlled collisions of a single atom and ion guided by movable
trapping potentials | null | We consider a system composed of a trapped atom and a trapped ion. The ion charge induces in the atom an electric dipole moment, which attracts it with an r^{-4} dependence at large distances. In the regime considered here, the characteristic range of the atom-ion interaction is comparable or larger than the characteristic size of the trapping potential, which excludes the application of the contact pseudopotential. The short-range part of the interaction is described in the framework of quantum-defect theory, by introducing some short-range parameters, which can be related to the s-wave scattering length. When the separation between traps is changed we observe trap-induced shape resonances between molecular bound states and vibrational states of the external trapping potential. Our analysis is extended to quasi-one-dimensional geometries, when the scattering exhibit confinement-induced resonances, similar to the ones studied before for short-range interactions. For quasi-one-dimensi |
23ae01ab-8fed-457d-99bd-5d94bb8a89d5 | 23ae01ab-8fed-457d-99bd-5d94bb8a89d5 | 23ae01ab-8fed-457d-99bd-5d94bb8a89d5 | human | null | null | none | abstracts | Counting BPS operators in N=4 SYM | null | The free field partition function for a generic U(N) gauge theory, where the fundamental fields transform in the adjoint representation, is analysed in terms of symmetric polynomial techniques. It is shown by these means how this is related to the cycle polynomial for the symmetric group and how the large N result may be easily recovered. Higher order corrections for finite N are also discussed in terms of symmetric group characters. For finite N, the partition function involving a single bosonic fundamental field is recovered and explicit counting of multi-trace quarter BPS operators in free \N=4 super Yang Mills discussed, including a general result for large N. The partition function for BPS operators in the chiral ring of \N=4 super Yang Mills is analysed in terms of plane partitions. Asymptotic counting of BPS primary operators with differing R-symmetry charges is discussed in both free \N=4 super Yang Mills and in the chiral ring. Also, general and explicit expressions are deri |
0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | 0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | 0aaf6ac5-3cb1-440c-8d3c-fd8640487c70 | human | null | null | none | abstracts | The redshift and geometrical aspect of photons | null | The cosmological redshift phenomenon can be described by the dark matter field fluid model, the results deduced from this model agree very well with the observations. The observed cosmological redshift of light depends on both the speed of the emitter and the distance between the emitter and the observer. If the emitter moves away from us, a redshift is observed. If the emitter moves towards us, whether a redshift, a blueshift or no shift is observed will depend on the speed vs. the distance. If the speed is in the range of c(exp[-beta*D]-1) < v < 0, a redshift is observed; if the speed equals c(exp[-beta*D]-1), no shift is observed; if the speed v less than c(exp[-beta*D]-1), a blueshift is observed. A redshift will be always observed in all directions for any celestial objects as long as their distance from us is large enough. Therefore, many more redshifts than blueshifts should be observed for galaxies and supernovae, etc in the sky. This conclusion agrees with current observatio |
9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | 9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | 9d8253d5-dffc-4ec0-9d4c-3ad792dd1180 | human | null | null | none | abstracts | Cool Stars in Hot Places | null | During the last three decades, evidence has mounted that star and planet formation is not an isolated process, but is influenced by current and previous generations of stars. Although cool stars form in a range of environments, from isolated globules to rich embedded clusters, the influences of other stars on cool star and planet formation may be most significant in embedded clusters, where hundreds to thousands of cool stars form in close proximity to OB stars. At the cool stars 14 meeting, a splinter session was convened to discuss the role of environment in the formation of cool stars and planetary systems; with an emphasis on the ``hot'' environment found in rich clusters. We review here the basic results, ideas and questions presented at the session. We have organized this contribution into five basic questions: what is the typical environment of cool star formation, what role do hot star play in cool star formation, what role does environment play in planet formation, what is t |
f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | f81c8a46-f32b-4c43-bf3a-8ab6eb8ee507 | human | null | null | none | abstracts | Bar-Halo Friction in Galaxies III: Particle Number Requirements for
Simulations | null | The question whether the dark matter halo density in the centers of galaxies could be changed through interactions with a rotating bar in the baryonic disk is of considerable current interest. While N-body simulations have been used to address this question, it has also been claimed that results from such simulations cannot be trusted. Based on a perturbative treatment of resonant exchanges between orbits and a rotating perturbation, Weinberg & Katz contend that N-body simulations of this process will not reveal the continuum result unless many more than the usual numbers of particles are employed. Here I report a study designed to examine their contention, finding results that show no dependence on the number of particles over the range usually employed up to that advocated by these authors. I show that my results are independent of all numerical parameters, and that field methods perform equally with grid methods in this respect. I also identify the reasons that the required partic |
2606b910-fe8d-4a6d-992e-3bc896f12bc7 | 2606b910-fe8d-4a6d-992e-3bc896f12bc7 | 2606b910-fe8d-4a6d-992e-3bc896f12bc7 | human | null | null | none | abstracts | Geometry of Time, Axiom of Choice and Neuro-Biological Quantum Zeno
Effect | null | Role of axiom of choice in quantum measurement is highlighted by suggesting that the conscious observer chooses the outcome from a mixed state. Further, in a periodically repeating universe, these outcomes must be pre-recorded within the non-physical conscious observers, which precludes free will. Free will however exists in a universe with open time, It is suggested that psychology's binding problem is connected with Cantor's original definition of set. Influence of consciousness on material outcome through quantum processes is discussed and interesting constraints derived. For example, it is predicted that quantum mechanical brain states should get frozen if monitored at sufficiently small space-time intervals - a neuro-biological version of the so called quantum zeno effect, which has been verified in domain of micro-physics. Existence of a very small micro-mini-black-hole in brain is predicted as a space-time structural interface between consciousness and brain, whose vaporizatio |
14e44409-7271-45a4-be40-35a2f0e2203f | 14e44409-7271-45a4-be40-35a2f0e2203f | 14e44409-7271-45a4-be40-35a2f0e2203f | human | null | null | none | abstracts | Probing the Structure of Gamma-Ray Burst Jets with Steep Decay Phase of
their Early X-ray Afterglows | null | We show that the jet structure of gamma-ray bursts (GRBs) can be investigated with the tail emission of the prompt GRB. The tail emission which we consider is identified as a steep-decay component of the early X-ray afterglow observed by the X-ray Telescope onboard Swift. Using a Monte Carlo method, we derive, for the first time, the distribution of the decay index of the GRB tail emission for various jet models. The new definitions of the zero of time and the time interval of a fitting region are proposed. These definitions for fitting the light curve lead us an unique definition of the decay index, which is useful to investigate the structure of the GRB jet. We find that if the GRB jet has a core-envelope structure, the predicted distribution of the decay index of the tail has a wide scatter and has multiple peaks, which cannot be seen for the case of the uniform and the Gaussian jet. Therefore, the decay index distribution tells us the information on the jet structure. Especially, |
dd1e2faf-cded-456c-a21a-0e81db7d2e3d | dd1e2faf-cded-456c-a21a-0e81db7d2e3d | dd1e2faf-cded-456c-a21a-0e81db7d2e3d | human | null | null | none | abstracts | Excitation Spectrum Gap and Spin-Wave Stiffness of XXZ Heisenberg
Chains: Global Renormalization-Group Calculation | null | The anisotropic XXZ spin-1/2 Heisenberg chain is studied using renormalization-group theory. The specific heats and nearest-neighbor spin-spin correlations are calculated thoughout the entire temperature and anisotropy ranges in both ferromagnetic and antiferromagnetic regions, obtaining a global description and quantitative results. We obtain, for all anisotropies, the antiferromagnetic spin-liquid spin-wave velocity and the Isinglike ferromagnetic excitation spectrum gap, exhibiting the spin-wave to spinon crossover. A number of characteristics of purely quantum nature are found: The in-plane interaction s_i^x s_j^x + s_i^y s_j^y induces an antiferromagnetic correlation in the out-of-plane s_i^z component, at higher temperatures in the antiferromagnetic XXZ chain, dominantly at low temperatures in the ferromagnetic XXZ chain, and, in-between, at all temperatures in the XY chain. We find that the converse effect also occurs in the antiferromagnetic XXZ chain: an antiferromagnetic s_ |
cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | cdb10ff6-8e93-43ba-84a6-5090c0b82f58 | human | null | null | none | abstracts | Observations on degenerate saddle point problems | null | We investigate degenerate saddle point problems, which can be viewed as limit cases of standard mixed formulations of symmetric problems with large jumps in coefficients. We prove that they are well-posed in a standard norm despite the degeneracy. By wellposedness we mean a stable dependence of the solution on the right-hand side. A known approach of splitting the saddle point problem into separate equations for the primary unknown and for the Lagrange multiplier is used. We revisit the traditional Ladygenskaya--Babu\v{s}ka--Brezzi (LBB) or inf--sup condition as well as the standard coercivity condition, and analyze how they are affected by the degeneracy of the corresponding bilinear forms. We suggest and discuss generalized conditions that cover the degenerate case. The LBB or inf--sup condition is necessary and sufficient for wellposedness of the problem with respect to the Lagrange multiplier under some assumptions. The generalized coercivity condition is necessary and sufficient |
3128efea-83a6-4369-bcb3-11cf3dae45c8 | 3128efea-83a6-4369-bcb3-11cf3dae45c8 | 3128efea-83a6-4369-bcb3-11cf3dae45c8 | human | null | null | none | abstracts | Expected Planets in Globular Clusters | null | We argue that all transient searches for planets in globular clusters have a very low detection probability. Planets of low metallicity stars typically do not reside at small orbital separations. The dependance of planetary system properties on metallicity is clearly seen when the quantity Ie=Mp[a(1-e)]^2 is considered; Mp, a, e, are the planet mass, semi-major axis, and eccentricity, respectively. In high metallicity systems there is a concentration of systems at high and low values of Ie, with a low-populated gap near Ie~0.3 M_J AU^2, where M_J is Jupiter's mass. In low metallicity systems the concentration is only at the higher range of I_e, with a tail to low values of Ie. Therefore, it is still possible that planets exist around main sequence stars in globular clusters, although at small numbers because of the low metallicity, and at orbital periods of >~10 days. We discuss the implications of our conclusions on the role that companions can play in the evolution of their parent |
b01f521f-681c-470d-996a-1dce6f466de3 | b01f521f-681c-470d-996a-1dce6f466de3 | b01f521f-681c-470d-996a-1dce6f466de3 | human | null | null | none | abstracts | Instanton Induced Neutrino Majorana Masses in CFT Orientifolds with
MSSM-like spectra | null | Recently it has been shown that string instanton effects may give rise to neutrino Majorana masses in certain classes of semi-realistic string compactifications. In this paper we make a systematic search for supersymmetric MSSM-like Type II Gepner orientifold constructions admitting boundary states associated with instantons giving rise to neutrino Majorana masses and other L- and/or B-violating operators. We analyze the zero mode structure of D-brane instantons on general type II orientifold compactifications, and show that only instantons with O(1) symmetry can have just the two zero modes required to contribute to the 4d superpotential. We however discuss how the addition of fluxes and/or possible non-perturbative extensions of the orientifold compactifications would allow also instantons with $Sp(2)$ and U(1) symmetries to generate such superpotentials. In the context of Gepner orientifolds with MSSM-like spectra, we find no models with O(1) instantons with just the required zero |
483ba0a1-c8e7-484c-9a38-e834fe50cc8b | 483ba0a1-c8e7-484c-9a38-e834fe50cc8b | 483ba0a1-c8e7-484c-9a38-e834fe50cc8b | human | null | null | none | abstracts | Vacuum Energy and Renormalization on the Edge | null | The vacuum dependence on boundary conditions in quantum field theories is analysed from a very general viewpoint. From this perspective the renormalization prescriptions not only imply the renormalization of the couplings of the theory in the bulk but also the appearance of a flow in the space of boundary conditions. For regular boundaries this flow has a large variety of fixed points and no cyclic orbit. The family of fixed points includes Neumann and Dirichlet boundary conditions. In one-dimensional field theories pseudoperiodic and quasiperiodic boundary conditions are also RG fixed points. Under these conditions massless bosonic free field theories are conformally invariant. Among all fixed points only Neumann boundary conditions are infrared stable fixed points. All other conformal invariant boundary conditions become unstable under some relevant perturbations. In finite volumes we analyse the dependence of the vacuum energy along the trajectories of the renormalization group fl |
00282bc5-15ba-4988-8b56-01ffb8a80186 | 00282bc5-15ba-4988-8b56-01ffb8a80186 | 00282bc5-15ba-4988-8b56-01ffb8a80186 | human | null | null | none | abstracts | Higher harmonics increase LISA's mass reach for supermassive black holes | null | Current expectations on the signal to noise ratios and masses of supermassive black holes which the Laser Interferometer Space Antenna (LISA) can observe are based on using in matched filtering only the dominant harmonic of the inspiral waveform at twice the orbital frequency. Other harmonics will affect the signal-to-noise ratio of systems currently believed to be observable by LISA. More significantly, inclusion of other harmonics in our matched filters would mean that more massive systems that were previously thought to be {\it not} visible in LISA should be detectable with reasonable SNRs. Our estimates show that we should be able to significantly increase the mass reach of LISA and observe the more commonly occurring supermassive black holes of masses $\sim 10^8M_\odot.$ More specifically, with the inclusion of all known harmonics LISA will be able to observe even supermassive black hole coalescences with total mass $\sim 10^8 M_\odot (10^9M_\odot)$ (and mass-ratio 0.1) for a lo |
616e071c-207c-4047-9b16-fc5dcd2401cf | 616e071c-207c-4047-9b16-fc5dcd2401cf | 616e071c-207c-4047-9b16-fc5dcd2401cf | human | null | null | none | abstracts | SUBARU HDS Observations of a Balmer-Dominated Shock in Tycho's Supernova
Remnant | null | We present an Ha spectral observation of a Balmer-dominated shock on the eastern side of Tycho's supernova remnant using the Subaru Telescope. Utilizing the High Dispersion Spectrograph (HDS), we measure the spatial variation of the line profile between preshock and postshock gas. Our observation clearly shows a broadening and centroid shift of the narrow-component postshock Ha line relative to the Ha emission from the preshock gas. The observation supports the existence of a thin precursor where gas is heated and accelerated ahead of the shock. Furthermore, the spatial profile of the emission ahead of the Balmer filament shows a gradual gradient in the Ha intensity and line width ahead of the shock. We propose that this region (~10^16 cm) is likely to be the spatially resolved precursor. The line width increases from ~30 up to ~45 km/s, and its central velocity shows a redshift of ~5 km/s across the shock front. The characteristics of the precursor are consistent with a cosmic-ray p |
20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | 20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | 20b5f6bc-2dad-4e80-932f-fce3e4d82cbb | human | null | null | none | abstracts | Orbits of tori extended by finite groups and their polynomial hulls: the
case of connected complex orbits | null | Let $V$ be a complex linear space, $G\subset\GL(V)$ be a compact group. We consider the problem of description of polynomial hulls $\wh{Gv}$ for orbits $Gv$, $v\in V$, assuming that the identity component of $G$ is a torus $T$. The paper contains a universal construction for orbits which satisfy the inclusion $Gv\subset T^\bbC v$ and a characterization of pairs $(G,V)$ such that it is true for a generic $v\in V$. The hull of a finite union of $T$-orbits in $T^\bbC v$ can be distinguished in $\clos T^\bbC v$ by a finite collection of inequalities of the type $\abs{z_1}^{s_1}...\abs{z_n}^{s_n}\leq c$. In particular, this is true for $Gv$. If powers in the monomials are independent of $v$, $Gv\subset T^\bbC v$ for a generic $v$, and either the center of $G$ is finite or $T^\bbC$ has an open orbit, then the space $V$ and the group $G$ are products of standard ones; the latter means that $G=S_nT$, where $S_n$ is the group of all permutations of coordinates and $T$ is either $\bbT^n$ or $\ |
afa87975-d667-4919-9360-1f98b01f0ab4 | afa87975-d667-4919-9360-1f98b01f0ab4 | afa87975-d667-4919-9360-1f98b01f0ab4 | human | null | null | none | abstracts | Zero-temperature resistive transition in Josephson-junction arrays at
irrational frustration | null | We use a driven Monte Carlo dynamics in the phase representation to determine the linear resistivity and current-voltage scaling of a two-dimensional Josephson-junction array at an irrational flux quantum per plaquette. The results are consistent with a phase-coherence transition scenario where the critical temperature vanishes. The linear resistivity is nonzero at any finite temperatures but nonlinear behavior sets in at a temperature-dependent crossover current determined by the thermal critical exponent. From a dynamic scaling analysis we determine this critical exponent and the thermally activated behavior of the linear resistivity. The results are in agreement with earlier calculations using the resistively shunted-junction model for the dynamics of the array. The linear resistivity behavior is consistent with some experimental results on arrays of superconducting grains but not on wire networks, which we argue have been obtained in a current regime above the crossover current. |
91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | 91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | 91bbb76e-8e4c-451a-a84f-0e29cd34f3bb | human | null | null | none | abstracts | Protostellar clusters in intermediate-mass (IM) star forming regions | null | The transition between the low density groups of T Tauri stars and the high density clusters around massive stars occurs in the intermediate-mass (IM) range (M$_*$$\sim$2--8 M$_\odot$). High spatial resolution studies of IM young stellar objects (YSO) can provide important clues to understand the clustering in massive star forming regions. Aims: Our aim is to search for clustering in IM Class 0 protostars. The high spatial resolution and sensitivity provided by the new A configuration of the Plateau de Bure Interferometer (PdBI) allow us to study the clustering in these nearby objects. Methods: We have imaged three IM Class 0 protostars (Serpens-FIRS 1, IC 1396 N, CB 3) in the continuum at 3.3 and 1.3mm using the PdBI. The sources have been selected with different luminosity to investigate the dependence of the clustering process on the luminosity of the source. Results: Only one millimeter (mm) source is detected towards the low luminosity source Serpens--FIRS 1. Towards CB 3 |
2565412d-e295-4e87-a876-09f367615aa8 | 2565412d-e295-4e87-a876-09f367615aa8 | 2565412d-e295-4e87-a876-09f367615aa8 | human | null | null | none | abstracts | Transitive powers of Young-Jucys-Murphy elements are central | null | Although powers of the Young-Jucys-Murphya elements X_i = (1 i) + ... +(i-1 i), i = 1, ..., n, in the symmetric group S_n acting on {1, ...,n} do not lie in the centre of the group algebra of S_n, we show that transitive powers, namely the sum of the contributions from elements that act transitively on {1, >...,n}, are central. We determine the coefficients, which we call star factorization numbers, that occur in the resolution of transitive powers with respect to the class basis of the centre of S_n, and show that they have a polynomiality property. These centrality and polynomiality properties have seemingly unrelated consequences. First, they answer a question raised by Pak about reduced decompositions; second, they explain and extend the beautiful symmetry result discovered by Irving and Rattan; and thirdly, we relate the polynomiality to an existing polynomiality result for a class of double Hurwitz numbers associated with branched covers of the sphere, which therefore suggests |
99db9a57-51de-43ca-aa5b-72b000c933df | 99db9a57-51de-43ca-aa5b-72b000c933df | 99db9a57-51de-43ca-aa5b-72b000c933df | human | null | null | none | abstracts | Spin Dynamics Of $qqq$ Wave Function On Light Front In High Momentum
Limit Of QCD : Role Of $qqq$ Force | null | The contribution of a spin-rich $qqq$ force (in conjunction with pairwise $qq$ forces) to the analytical structure of the $qqq$ wave function is worked out in the high momentum regime of QCD where the confining interaction may be ignored, so that the dominant effect is $Coulombic$. A distinctive feature of this study is that the spin-rich $qqq$ force is generated by a $ggg$ vertex (a genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on as many quark lines, giving rise to a (Mercedes-Benz type) $Y$-shaped diagram. The dynamics is that of a Salpeter-like equation (3D support for the kernel) formulated covariantly on the light front, a la Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these ingredients, the differential equation for the 3D wave function $\phi$ receives well-defined contributions from the $qq$ and $qqq$ forces. In partic |
c5ab6ac9-4255-4991-a183-795a846596b1 | c5ab6ac9-4255-4991-a183-795a846596b1 | c5ab6ac9-4255-4991-a183-795a846596b1 | human | null | null | none | abstracts | QCD in One Dimension at Nonzero Chemical Potential | null | Using an integration formula recently derived by Conrey, Farmer and Zirnbauer, we calculate the expectation value of the phase factor of the fermion determinant for the staggered lattice QCD action in one dimension. We show that the chemical potential can be absorbed into the quark masses; the theory is in the same chiral symmetry class as QCD in three dimensions at zero chemical potential. In the limit of a large number of colors and fixed number of lattice points, chiral symmetry is broken spontaneously, and our results are in agreement with expressions based on a chiral Lagrangian. In this limit, the eigenvalues of the Dirac operator are correlated according to random matrix theory for QCD in three dimensions. The discontinuity of the chiral condensate is due to an alternative to the Banks-Casher formula recently discovered for QCD in four dimensions at nonzero chemical potential. The effect of temperature on the average phase factor is discussed in a schematic random matrix model |
f12226e0-3a35-4092-ba5c-a5078804f2cb | f12226e0-3a35-4092-ba5c-a5078804f2cb | f12226e0-3a35-4092-ba5c-a5078804f2cb | human | null | null | none | abstracts | The VLT-FLAMES survey of massive stars: Wind properties and evolution of
hot massive stars in the LMC | null | [Abridged] We have studied the optical spectra of 28 O- and early B-type stars in the Large Magellanic Cloud, 22 of which are associated with the young star-forming region N11. Stellar parameters are determined using an automated fitting method, combining the stellar atmosphere code FASTWIND with the genetic-algorithm optimisation routine PIKAIA. Results for stars in the LH9 and LH10 associations of N11 are consistent with a sequential star formation scenario, in which activity in LH9 triggered the formation of LH10. Our sample contains four stars of spectral type O2, of which the hottest is found to be ~49-54 kK (cf. ~45-46 kK for O3 stars). The masses of helium-enriched dwarfs and giants are systematically lower than those implied by non-rotating evolutionary tracks. We interpret this as evidence for efficient rotationally-enhanced mixing, leading to the surfacing of primary helium and to an increase of the stellar luminosity. This result is consistent with findings for SMC stars b |
f97779e6-0928-4999-a406-a41fe882ec36 | f97779e6-0928-4999-a406-a41fe882ec36 | f97779e6-0928-4999-a406-a41fe882ec36 | human | null | null | none | abstracts | Strange Nucleon Form Factors from $ep$ and $\nu p$ Elastic Scattering | null | The recent parity-violating $ep$ forward-scattering elastic asymmetry data from Jefferson Lab (HAPPEx and G0), when combined with the $\nu p$ elastic cross section data from Brookhaven (E734), permit an extraction of the strangeness contribution to the vector and axial nucleon form factors for momentum transfers in the range $0.45 < Q^2 < 1.0$ GeV$^2$. These results, combined with the recent determination of the strange vector form factors at $Q^2 = 0.1$ GeV$^2$ (SAMPLE, HAPPEx, PVA4, G0) have been interpreted in terms of $uuds\bar{s}$ configurations very different from the kaon-loop configurations usually associated with strangeness in the nucleon. New experiments are being proposed to improve the state of our knowledge of the $\nu p$ elastic cross section -- these new experiments will push the range of $Q^2$ to much lower values, and greatly increase the precision of the $\nu p$ elastic data. One outcome of this can be a measurement of the strangeness contribution to the nucleon sp |
bfb49b19-2598-42d6-9413-900366861144 | bfb49b19-2598-42d6-9413-900366861144 | bfb49b19-2598-42d6-9413-900366861144 | human | null | null | none | abstracts | VIMOS-VLT spectroscopy of the giant Ly-alpha nebulae associated with
three z~2.5 radio galaxies | null | The morphological and spectroscopic properties of the giant (>60 kpc) Ly-alpha nebulae associated with three radio galaxies at z~2.5 (MRC 1558-003, MRC 2025-218 and MRC 0140-257) have been investigated using integral field spectroscopic data obtained with VIMOS on VLT. The morphologies are varied. The nebula of one source has a centrally peaked, rounded appearance. In the other two objects, it consists of two spatial components. The three nebulae are aligned with the radio axis within <30 deg. The total Ly-alpha luminosities are in the range (0.3-3.4) x 1e44 erg s-1. The Ly-alpha spectral profile shows strong variation through the nebulae, with FWHM values in the range ~400-1500 km s-1 and velocity shifts V~120-600 km s-1. We present an infall model which can explain successfully most Ly-alpha morphological and spectroscopic properties of the nebula associated with MRC 1558-003. This adds further support to our previous conclusion that the _quiescent_ giant nebulae associated wit |
5f72a075-06a0-4314-b3f1-c378e5034a9a | 5f72a075-06a0-4314-b3f1-c378e5034a9a | 5f72a075-06a0-4314-b3f1-c378e5034a9a | human | null | null | none | abstracts | "Illusion of control" in Minority and Parrondo Games | null | Human beings like to believe they are in control of their destiny. This ubiquitous trait seems to increase motivation and persistence, and is probably evolutionarily adaptive. But how good really is our ability to control? How successful is our track record in these areas? There is little understanding of when and under what circumstances we may over-estimate or even lose our ability to control and optimize outcomes, especially when they are the result of aggregations of individual optimization processes. Here, we demonstrate analytically using the theory of Markov Chains and by numerical simulations in two classes of games, the Minority game and the Parrondo Games, that agents who optimize their strategy based on past information actually perform worse than non-optimizing agents. In other words, low-entropy (more informative) strategies under-perform high-entropy (or random) strategies. This provides a precise definition of the "illusion of control" in set-ups a priori defined to em |
83186c52-bc1c-4bed-89dd-e90f81770cfa | 83186c52-bc1c-4bed-89dd-e90f81770cfa | 83186c52-bc1c-4bed-89dd-e90f81770cfa | human | null | null | none | abstracts | Investigation of Energy Spectrum of EGRET Gamma-ray Sources by an
Extensive Air Shower Experiment | null | Ultra-High-Energy (UHE) ($E>100 $TeV) Extensive Air Showers (EASs) have been monitored for a period of five years (1997-2003), using a small array of scintillation detectors in Tehran, Iran. The data have been analyzed to take in to account of the dependence of source counts on zenith angle. Because of varying thickness of the overlaying atmosphere, the shower count rate is extremely dependent on zenith angle. During a calendar year different sources come in the field of view of the array at varying zenith angles and have different effective observation time equivalent to zenith in a day. High energy gamma-ray sources from the EGRET third catalogue where observed and the data were analyzed using an excess method. Upper limits were obtained for 10 EGRET sources. Then we investigated the EAS event rates for these 10 sources and obtained a flux for each of them using parameters of our experiment results and simulations. Finally we investigated the gamma-ray spectrum in the UHE range usi |
7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | 7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | 7c52b72f-42a0-4de6-8d72-d7c08c9fb1ac | human | null | null | none | abstracts | Conjugate field and fluctuation-dissipation relation for the dynamic
phase transition in the two-dimensional kinetic Ising model | null | The two-dimensional kinetic Ising model, when exposed to an oscillating applied magnetic field, has been shown to exhibit a nonequilibrium, second-order dynamic phase transition (DPT), whose order parameter Q is the period-averaged magnetization. It has been established that this DPT falls in the same universality class as the equilibrium phase transition in the two-dimensional Ising model in zero applied field. Here we study for the first time the scaling of the dynamic order parameter with respect to a nonzero, period-averaged, magnetic `bias' field, H_b, for a DPT produced by a square-wave applied field. We find evidence that the scaling exponent, \delta_d, of H_b at the critical period of the DPT is equal to the exponent for the critical isotherm, \delta_e, in the equilibrium Ising model. This implies that H_b is a significant component of the field conjugate to Q. A finite-size scaling analysis of the dynamic order parameter above the critical period provides further support for |
0fd11579-566b-40e7-adeb-13f8a3df5891 | 0fd11579-566b-40e7-adeb-13f8a3df5891 | 0fd11579-566b-40e7-adeb-13f8a3df5891 | human | null | null | none | abstracts | High Galactic Latitude Interstellar Neutral Hydrogen Structure and
Associated (WMAP) High Frequency Continuum Emission | null | Spatial associations have been found between interstellar neutral hydrogen (HI) emission morphology and small-scale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP) in an area bounded by l = 60 & 180 deg, b = 30 & 70 deg, which was the primary target for this study. This area is marked by the presence of highly disturbed local HI and a preponderance of intermediate- and high-velocity gas. The HI distribution toward the brightest peaks in the WMAP Internal Linear Combination (ILC) map for this area is examined and by comparing with a second area on the sky it is demonstrated that the associations do not appear to be the result of chance coincidence. Close examination of several of the associations reveals important new properties of diffuse interstellar neutral hydrogen structure. In the case of high-velocity cloud MI, the HI and WMAP ILC morphologies are similar and an excess of soft X-ray emission and H-alpha emission have been reported for this feature. It is s |
05eec130-a2ef-4f27-b9e0-d8e146db263c | 05eec130-a2ef-4f27-b9e0-d8e146db263c | 05eec130-a2ef-4f27-b9e0-d8e146db263c | human | null | null | none | abstracts | Did time begin? Will time end? | null | Did time begin at a Big Bang? Will the present expansion of the universe last for a finite or infinite time? These questions sound philosophical but are becoming, now in the twenty-first century, central to the scientific study of cosmology. The answers, which should become clarified in the next decade or two, could have profound implications for how we see our own role in the universe. Since the original publication of Stephen Hawking's {\it A Brief History of Time} in 1988, the answers to these questions have progressed as a result of research by the community of active theoretical physicists including myself. To present the underlying ideas requires discussion of a wide range of topics in cosmology, especially the make up of the energy content of the universe. A brief summary of my conclusions, that of three different possibilities concerning the history and future of time, the least likely is the conventional wisdom (time began and will never end) and most likely is a cyclic mode |
9b85ffff-712d-46f7-b5ab-ca48e28e2155 | 9b85ffff-712d-46f7-b5ab-ca48e28e2155 | 9b85ffff-712d-46f7-b5ab-ca48e28e2155 | human | null | null | none | abstracts | Experimental and theoretical study of light scattering by individual
mature red blood cells by use of scanning flow cytometry and discrete dipole
approximation | null | Elastic light scattering by mature red blood cells (RBCs) was theoretically and experimentally analyzed with the discrete dipole approximation (DDA) and the scanning flow cytometry (SFC), respectively. SFC permits measurement of angular dependence of light-scattering intensity (indicatrix) of single particles. A mature RBC is modeled as a biconcave disk in DDA simulations of light scattering. We have studied the effect of RBC orientation related to the direction of the incident light upon the indicatrix. Numerical calculations of indicatrices for several aspect ratios and volumes of RBC have been carried out. Comparison of the simulated indicatrices and indicatrices measured by SFC showed good agreement, validating the biconcave disk model for a mature RBC. We simulated the light-scattering output signals from the SFC with the DDA for RBCs modeled as a disk-sphere and as an oblate spheroid. The biconcave disk, the disk-sphere, and the oblate spheroid models have been compared for two |
d343c0ad-bce5-4ef7-85b0-f1ba449a666b | d343c0ad-bce5-4ef7-85b0-f1ba449a666b | d343c0ad-bce5-4ef7-85b0-f1ba449a666b | human | null | null | none | abstracts | Lattice refining loop quantum cosmology, anisotropic models and
stability | null | A general class of loop quantizations for anisotropic models is introduced and discussed, which enhances loop quantum cosmology by relevant features seen in inhomogeneous situations. The main new effect is an underlying lattice which is being refined during dynamical changes of the volume. In general, this leads to a new feature of dynamical difference equations which may not have constant step-size, posing new mathematical problems. It is discussed how such models can be evaluated and what lattice refinements imply for semiclassical behavior. Two detailed examples illustrate that stability conditions can put strong constraints on suitable refinement models, even in the absence of a fundamental Hamiltonian which defines changes of the underlying lattice. Thus, a large class of consistency tests of loop quantum gravity becomes available. In this context, it will also be seen that quantum corrections due to inverse powers of metric components in a constraint are much larger than they a |
5ab941e3-7c77-463f-9387-8e73887f3b4c | 5ab941e3-7c77-463f-9387-8e73887f3b4c | 5ab941e3-7c77-463f-9387-8e73887f3b4c | human | null | null | none | abstracts | Challenges for MSSM Higgs searches at Hadron Colliders | null | In this article we analyze the impact of B-physics and Higgs physics at LEP on standard and non-standard Higgs bosons searches at the Tevatron and the LHC, within the framework of minimal flavor violating supersymmetric models. The B-physics constraints we consider come from the experimental measurements of the rare B-decays b -> s gamma and B_u -> tau nu and the experimental limit on the B_s -> mu+ mu- branching ratio. We show that these constraints are severe for large values of the trilinear soft breaking parameter A_t, rendering the non-standard Higgs searches at hadron colliders less promising. On the contrary these bounds are relaxed for small values of A_t and large values of the Higgsino mass parameter mu, enhancing the prospects for the direct detection of non-standard Higgs bosons at both colliders. We also consider the available ATLAS and CMS projected sensitivities in the standard model Higgs search channels, and we discuss the LHC's ability in probing the whole MSSM para |
ca00443b-e716-46f2-af69-47b02d7cbeae | ca00443b-e716-46f2-af69-47b02d7cbeae | ca00443b-e716-46f2-af69-47b02d7cbeae | human | null | null | none | abstracts | The Plasma Puddle as a Perturbative Black Hole | null | We argue that the weak coupling regime of a large N gauge theory in the Higgs phase contains black hole-like objects. These so-called ``plasma puddles'' are meta-stable lumps of hot plasma lying in locally un-Higgsed regions of space. They decay via O(1/N) thermal radiation and, perhaps surprisingly, absorb all incident matter. We show that an incident particle of energy E striking the plasma puddle will shower into an enormous number of decay products whose multiplicity grows linearly with E, and whose average energy is independent of E. Once these ultra-soft particles reach the interior they are thermalized by the plasma within, and so the object appears ``black.'' We determine some gross properties like the size and temperature of the the plasma puddle in terms of fundamental parameters in the gauge theory. Interestingly, demanding that the plasma puddle emit thermal Hawking radiation implies that the object is black (i.e. absorbs all incident particles), which implies classical s |
6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | 6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | 6819ab6c-dcf5-4ddf-9910-2f54b1427b25 | human | null | null | none | abstracts | Aspects of stochastic resonance in reaction-diffusion systems: The
nonequilibrium-potential approach | null | We analyze several aspects of the phenomenon of stochastic resonance in reaction-diffusion systems, exploiting the nonequilibrium potential's framework. The generalization of this formalism (sketched in the appendix) to extended systems is first carried out in the context of a simplified scalar model, for which stationary patterns can be found analytically. We first show how system-size stochastic resonance arises naturally in this framework, and then how the phenomenon of array-enhanced stochastic resonance can be further enhanced by letting the diffusion coefficient depend on the field. A yet less trivial generalization is exemplified by a stylized version of the FitzHugh-Nagumo system, a paradigm of the activator-inhibitor class. After discussing for this system the second aspect enumerated above, we derive from it -through an adiabatic-like elimination of the inhibitor field- an effective scalar model that includes a nonlocal contribution. Studying the role played by the range of |
9da8d715-cb2e-49ae-8e74-521a3bdeed23 | 9da8d715-cb2e-49ae-8e74-521a3bdeed23 | 9da8d715-cb2e-49ae-8e74-521a3bdeed23 | human | null | null | none | abstracts | Distortion of Gravitational-Wave Packets Due to their Self-Gravity | null | When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole (BH) binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released and the duration of the emission, scaled by the total binary mass, M. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of <~ 100M. For characteristic emission parameters at the final plunge between binary BHs of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of 0.001. Accounting for the wave distortion would significantly decrease the waveform extraction errors in |
a97cda63-75c6-4b3c-8470-6e46407f0605 | a97cda63-75c6-4b3c-8470-6e46407f0605 | a97cda63-75c6-4b3c-8470-6e46407f0605 | human | null | null | none | abstracts | Information, information processing and gravity | null | I discuss fundamental limits placed on information and information processing by gravity. Such limits arise because both information and its processing require energy, while gravitational collapse (formation of a horizon or black hole) restricts the amount of energy allowed in a finite region. Specifically, I use a criterion for gravitational collapse called the hoop conjecture. Once the hoop conjecture is assumed a number of results can be obtained directly: the existence of a fundamental uncertainty in spatial distance of order the Planck length, bounds on information (entropy) in a finite region, and a bound on the rate of information processing in a finite region. In the final section I discuss some cosmological issues related to the total amount of information in the universe, and note that almost all detailed aspects of the late universe are determined by the randomness of quantum outcomes. This paper is based on a talk presented at a 2007 Bellairs Research Institute (McGill Un |
4b36762b-96bb-40d0-ab76-47db42cb6e85 | 4b36762b-96bb-40d0-ab76-47db42cb6e85 | 4b36762b-96bb-40d0-ab76-47db42cb6e85 | human | null | null | none | abstracts | Noise-induced phase transitions: Effects of the noises' statistics and
spectrum | null | The local, uncorrelated multiplicative noises driving a second-order, purely noise-induced, ordering phase transition (NIPT) were assumed to be Gaussian and white in the model of [Phys. Rev. Lett. \textbf{73}, 3395 (1994)]. The potential scientific and technological interest of this phenomenon calls for a study of the effects of the noises' statistics and spectrum. This task is facilitated if these noises are dynamically generated by means of stochastic differential equations (SDE) driven by white noises. One such case is that of Ornstein--Uhlenbeck noises which are stationary, with Gaussian pdf and a variance reduced by the self-correlation time (\tau), and whose effect on the NIPT phase diagram has been studied some time ago. Another such case is when the stationary pdf is a (colored) Tsallis' (q)--\emph{Gaussian} which, being a \emph{fat-tail} distribution for (q>1) and a \emph{compact-support} one for (q<1), allows for a controlled exploration of the effects of the departure from |
3f314eb2-5238-40fd-a0db-2637d0a20b6d | 3f314eb2-5238-40fd-a0db-2637d0a20b6d | 3f314eb2-5238-40fd-a0db-2637d0a20b6d | human | null | null | none | abstracts | The Mid-Infrared Emission of M87 | null | We discuss Subaru and Spitzer Space Telescope imaging and spectroscopy of M87 in the mid-infrared from 5-35 um. These observations allow us to investigate mid-IR emission mechanisms in the core of M87 and to establish that the flaring, variable jet component HST-1 is not a major contributor to the mid-IR flux. The Spitzer data include a high signal-to-noise 15-35 $\mu$m spectrum of the knot A/B complex in the jet, which is consistent with synchrotron emission. However, a synchrotron model cannot account for the observed {\it nuclear} spectrum, even when contributions from the jet, necessary due to the degrading of resolution with wavelength, are included. The Spitzer data show a clear excess in the spectrum of the nucleus at wavelengths longer than 25 um, which we model as thermal emission from cool dust at a characteristic temperature of 55 \pm 10 K, with an IR luminosity \sim 10^{39} {\rm ~erg ~s^{-1}}. Given Spitzer's few-arcsecond angular resolution, the dust seen in the nuclear |
34e818e0-2103-4a94-a654-e922d3e54a9b | 34e818e0-2103-4a94-a654-e922d3e54a9b | 34e818e0-2103-4a94-a654-e922d3e54a9b | human | null | null | none | abstracts | A linear reformulation of the Kuramoto model of self-synchronizing
oscillators | null | The present paper introduces a linear reformulation of the Kuramoto model describing a self-synchronizing phase transition in a system of globally coupled oscillators that in general have different characteristic frequencies. The reformulated model provides an alternative coherent framework through which one can analytically tackle synchronization problems that are not amenable to the original Kuramoto analysis. It allows one to solve explicitly for the synchronization order parameter and the critical point of 1) the full phase-locking transition for a system with a finite number of oscillators (unlike the original Kuramoto model, which is solvable implicitly only in the mean-field limit) and 2) a new class of continuum systems. It also makes it possible to probe the system's dynamics as it moves towards a steady state. While discussion in this paper is restricted to systems with global coupling, the new formalism introduced by the linear reformulation also lends itself to solving sy |
9eac3f57-b52e-4a54-859d-190448bed60b | 9eac3f57-b52e-4a54-859d-190448bed60b | 9eac3f57-b52e-4a54-859d-190448bed60b | human | null | null | none | abstracts | Electronic Properties of Carbon Nanotubes Calculated from Density
Functional Theory and the Empirical pi-Bond Model | null | The validity of the DFT models implemented by FIREBALL for CNT electronic device modeling is assessed. The effective masses, band gaps, and transmission coefficients of semi-conducting, zigzag, (n,0) carbon nanotubes (CNTs) resulting from the ab initio tight-binding density functional theory (DFT) code FIREBALL and the empirical, nearest-neighbor pi-bond model are compared for all semiconducting n values 5 <(=) n <(=) 35. The DFT values for the effective masses differ from the pi-bond values by +(-) 9% over the range of n values, 17 <(=) n <(=) 29, most important for electronic device applications. Over the range 13 <(=) n <(=) 35, the DFT bandgaps are less than the empirical bandgaps by 20-180 meV depending on the functional and the n value. The pi-bond model gives results that differ signifcantly from the DFT results when the CNT diameter goes below 1 nm due to the large curvature of the CNT. The pi-bond model quickly becomes inaccurate away from the bandedges for a (10, 0) CNT, an |
f8394fc3-8915-4ab6-9906-111019d66fa1 | f8394fc3-8915-4ab6-9906-111019d66fa1 | f8394fc3-8915-4ab6-9906-111019d66fa1 | human | null | null | none | abstracts | Deaconstructing Functions on Quadratic Surfaces into Multipoles | null | Any homogeneous polynomial $P(x, y, z)$ of degree $d$, being restricted to a unit sphere $S^2$, admits essentially a unique representation of the form $\lambda + \sum_{k = 1}^d [\prod_{j = 1}^k L_{kj}]$, where $L_{kj}$'s are linear forms in $x, y$ and $z$ and $\lambda$ is a real number. The coefficients of these linear forms, viewed as 3D vectors, are called \emph{multipole} vectors of $P$. In this paper we consider similar multipole representations of polynomial and analytic functions on other quadratic surfaces $Q(x, y, z) = c$, real and complex. Over the complex numbers, the above representation is not unique, although the ambiguity is essentially finite. We investigate the combinatorics that depicts this ambiguity. We link these results with some classical theorems of harmonic analysis, theorems that describe decompositions of functions into sums of spherical harmonics. We extend these classical theorems (which rely on our understanding of the Laplace operator $\Delta_{S^2}$) to |
3bea52f9-dadc-4603-b1c9-418af4a7ae44 | 3bea52f9-dadc-4603-b1c9-418af4a7ae44 | 3bea52f9-dadc-4603-b1c9-418af4a7ae44 | human | null | null | none | abstracts | An Optical Source Catalog of the North Ecliptic Pole Region | null | We present a five (u*,g',r',i',z') band optical photometry catalog of the sources in the North Ecliptic Pole (NEP) region based on deep observations made with MegaCam at CFHT. The source catalog covers about 2 square degree area centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands, about 25 mag for i' band, and about 24 mag for z' band (4 sigma detection over an 1 arcsec aperture). The total number of cataloged sources brighter than r'= 23 mag is about 56,000 including both point sources and extended sources. From the investigation of photometric properties using the color-magnitude diagrams and color-color diagrams, we have found that the colors of extended sources are mostly (u*-r') < 3.0 and (g'-z') > 0.5. This can be used to separate the extended sources from the point sources reliably, even for the faint source domain where typical morphological classification schemes hardly work efficiently. We have derived an empirical color-redshift relation of the red |
b94adfd7-1c4c-48cb-b387-dfb3cacf55de | b94adfd7-1c4c-48cb-b387-dfb3cacf55de | b94adfd7-1c4c-48cb-b387-dfb3cacf55de | human | null | null | none | abstracts | The Kinematics and Dynamics of the Globular Clusters and the Planetary
Nebulae of NGC 5128 | null | A new kinematic and dynamic study of the halo of the giant elliptical galaxy, NGC 5128, is presented. From a spectroscopically confirmed sample of 340 globular clusters and 780 planetary nebulae, the rotation amplitude, rotation axis, velocity dispersion, and the total dynamical mass are determined for the halo of NGC 5128. The globular cluster kinematics were searched for both radial dependence and metallicity dependence by subdividing the globular cluster sample into 158 metal-rich ([Fe/H] > -1.0) and 178 metal-poor ([Fe/H] < -1.0) globular clusters. Our results show the kinematics of the metal-rich and metal-poor subpopulations are quite similar. The kinematics are compared to the planetary nebula population where differences are apparent in the outer regions of the halo. The total mass of NGC 5128 is found using the Tracer Mass estimator (Evans et al. 2003), to determine the mass supported by internal random motions, and the spherical component of the Jeans equation to determine |
1330efec-3f17-401f-9898-7019148d305f | 1330efec-3f17-401f-9898-7019148d305f | 1330efec-3f17-401f-9898-7019148d305f | human | null | null | none | abstracts | Five Intermediate-Period Planets from the N2K Sample | null | We report the detection of five Jovian mass planets orbiting high metallicity stars. Four of these stars were first observed as part of the N2K program and exhibited low RMS velocity scatter after three consecutive observations. However, follow-up observations over the last three years now reveal the presence of longer period planets with orbital periods ranging from 21 days to a few years. HD 11506 is a G0V star with a planet of \msini = 4.74 \mjup in a 3.85 year orbit. HD 17156 is a G0V star with a 3.12 \mjup planet in a 21.2 day orbit. The eccentricity of this orbit is 0.67, one of the highest known for a planet with a relatively short period. The orbital period for this planet places it in a region of parameter space where relatively few planets have been detected. HD 125612 is a G3V star with a planet of \msini = 3.5 \mjup in a 1.4 year orbit. HD 170469 is a G5IV star with a planet of \msini = 0.67 \mjup in a 3.13 year orbit. HD 231701 is an F8V star with planet of 1.08 \mjup in |
d5bc3512-c016-416e-8075-a32074504368 | d5bc3512-c016-416e-8075-a32074504368 | d5bc3512-c016-416e-8075-a32074504368 | human | null | null | none | abstracts | Statistical properties of giant pulses from the Crab pulsar | null | We have studied the statistics of giant pulses from the Crab pulsar for the first time with particular reference to their widths. We have analyzed data collected during 3.5 hours of observations conducted with the Westerbork Synthesis Radio Telescope operated in a tied-array mode at a frequency of 1200 MHz. The PuMa pulsar backend provided voltage recording of X and Y linear polarization states in two conjugate 10 MHz bands. We restricted the time resolution to 4 microseconds to match the scattering on the interstellar inhomogeneities. In total about 18000 giant pulses (GP) were detected in full intensity with a threshold level of 6 sigma. Cumulative probability distributions (CPD) of giant pulse energies were analyzed for groups of GPs with different effective widths in the range 4 to 65 microseconds. The CPDs were found to manifest notable differences for the different GP width groups. The slope of a power-law fit to the high-energy portion of the CPDs evolves from -1.7 to -3.2 whe |
68ce64c8-d0ed-461a-bef1-23bfbccdc481 | 68ce64c8-d0ed-461a-bef1-23bfbccdc481 | 68ce64c8-d0ed-461a-bef1-23bfbccdc481 | human | null | null | none | abstracts | The dynamics of Jupiter and Saturn in the gaseous proto-planetary disk | null | We study the possibility that the mutual interactions between Jupiter and Saturn prevented Type II migration from driving these planets much closer to the Sun. Our work extends previous results by Masset and Snellgrove (2001), by exploring a wider set of initial conditions and disk parameters, and by using a new hydrodynamical code that properly describes for the global viscous evolution of the disk. Initially both planets migrate towards the Sun, and Saturn's migration tends to be faster. As a consequence, they eventually end up locked in a mean motion resonance. If this happens in the 2:3 resonance, the resonant motion is particularly stable, and the gaps opened by the planets in the disk may overlap. This causes a drastic change in the torque balance for the two planets, which substantially slows down the planets' inward migration. If the gap overlap is substantial, planet migration may even be stopped or reversed. As the widths of the gaps depend on disk viscosity and scale heigh |
8849966b-eda6-476d-a233-170fdc6800ad | 8849966b-eda6-476d-a233-170fdc6800ad | 8849966b-eda6-476d-a233-170fdc6800ad | human | null | null | none | abstracts | Kinetic Theory for Binary Granular Mixtures at Low-Density | null | Many features of granular media can be modelled as a fluid of hard spheres with {\em inelastic} collisions. Under rapid flow conditions, the macroscopic behavior of grains can be described through hydrodynamic equations. At low-density, a fundamental basis for the derivation of the hydrodynamic equations and explicit expressions for the transport coefficients appearing in them is provided by the Boltzmann kinetic theory conveniently modified to account for inelastic binary collisions. The goal of this chapter is to give an overview of the recent advances made for binary granular gases by using kinetic theory tools. Some of the results presented here cover aspects such as transport properties, energy nonequipartition, instabilities, segregation or mixing, non-Newtonian behavior, .... In addition, comparison of the analytical results with those obtained from Monte Carlo and molecular dynamics simulations is also carried out, showing the reliability of kinetic theory to describe granula |
82a91266-71a9-4bb8-bea7-7e8118216554 | 82a91266-71a9-4bb8-bea7-7e8118216554 | 82a91266-71a9-4bb8-bea7-7e8118216554 | human | null | null | none | abstracts | Double Neutron Stars: Evidence For Two Different Neutron-Star Formation
Mechanisms | null | Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (< 0.27) indicating that their second-born neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of the second-born neutron stars in five of the six low-eccentricity double neutron stars are remarkably low (between 1.18 and 1.30 Msun). It is argued that these low-mass, low-kick neutron stars were formed by the electron-capture collapse of the degenerate O-Ne-Mg cores of helium stars less massive than about 3.5 Msun, whereas the higher-mass, higher kick-velocity neutron stars were formed by the collapses of the iron cores of higher initial mass. The absence of low-velocity single young radio pulsars (Hobbs et al. 2005) is consistent with the model proposed by Podsiadlowski et al. (2004), in which the |
e942129b-4424-4a4d-a24e-11292b872e89 | e942129b-4424-4a4d-a24e-11292b872e89 | e942129b-4424-4a4d-a24e-11292b872e89 | human | null | null | none | abstracts | A multi-transition molecular line study of candidate massive young
stellar objects associated with methanol masers | null | We characterize the molecular environment of candidate massive young stellar objects (MYSOs) signposted by methanol masers. Single pixel observations of 10 transitions of HCO^+, CO and CS isotopomers were carried out, using the IRAM 30m telescope. We studied a sample of 28 targets for which the 6.7GHz maser emission positions are known with a sub-arcsecond accuracy. The systemic velocity inferred from the optically thin lines agrees within 3km/s with the central velocity of the maser emission for most of the sources. About 64% of the sources show line wings in one or more transitions of CO, HCO^+ and CS species, indicating the presence of molecular outflows. Comparison of the widths of line wings and methanol maser emission suggests that the 6.7GHz maser line traces the environment of MYSO of various kinematic regimes. Therefore conditions conducive for the methanol maser can exist in the inner parts of molecular clouds or circumstellar discs as well as in the outer parts associated |
ea268c02-1cc4-4082-a501-12a8053263ea | ea268c02-1cc4-4082-a501-12a8053263ea | ea268c02-1cc4-4082-a501-12a8053263ea | human | null | null | none | abstracts | Patterns of dominant flows in the world trade web | null | The large-scale organization of the world economies is exhibiting increasingly levels of local heterogeneity and global interdependency. Understanding the relation between local and global features calls for analytical tools able to uncover the global emerging organization of the international trade network. Here we analyze the world network of bilateral trade imbalances and characterize its overall flux organization, unraveling local and global high-flux pathways that define the backbone of the trade system. We develop a general procedure capable to progressively filter out in a consistent and quantitative way the dominant trade channels. This procedure is completely general and can be applied to any weighted network to detect the underlying structure of transport flows. The trade fluxes properties of the world trade web determines a ranking of trade partnerships that highlights global interdependencies, providing information not accessible by simple local analysis. The present work |
424f2586-7144-4e15-903f-b7008083a687 | 424f2586-7144-4e15-903f-b7008083a687 | 424f2586-7144-4e15-903f-b7008083a687 | human | null | null | none | abstracts | Hydrogen 2p--2s transition: signals from the epochs of recombination and
reionization | null | We propose a method to study the epoch of reionization based on the possible observation of 2p--2s fine structure lines from the neutral hydrogen outside the cosmological H {\sc ii} regions enveloping QSOs and other ionizing sources in the reionization era. We show that for parameters typical of luminous sources observed at $z \simeq 6.3$ the strength of this signal, which is proportional to the H {\sc i} fraction, has a brightness temperature $\simeq 20 \mu K$ for a fully neutral medium. The fine structure line from this redshift is observable at $\nu \simeq 1 \rm GHz$ and we discuss prospects for the detection with several operational and future radio telescopes. We also compute the characteristics of this signal from the epoch of recombination: the peak brightness is expected to be $\simeq 100 \mu K$; this signal appears in the frequency range 5-10 MHz. The signal from the recombination era is nearly impossible to detect owing to the extreme brightness of the Galactic emission a |
629f021e-f787-439b-8ad3-a2b694175e90 | 629f021e-f787-439b-8ad3-a2b694175e90 | 629f021e-f787-439b-8ad3-a2b694175e90 | human | null | null | none | abstracts | CP Violation and Arrows of Time Evolution of a Neutral $K$ or $B$ Meson
from an Incoherent to a Coherent State | null | We study the evolution of a neutral $K$ meson prepared as an incoherent equal mixture of $K^0$ and $\bar{K^0}$. Denoting the density matrix by $\rho(t) = {1/2} N(t) [\1 + \vec{\zeta}(t) \cdot \vec{\sigma} ] $, the norm of the state $N(t)$ is found to decrease monotonically from one to zero, while the magnitude of the Stokes vector $|\vec{\zeta}(t)|$ increases monotonically from zero to one. This property qualifies these observables as arrows of time. Requiring monotonic behaviour of $N(t)$ for arbitrary values of $\gamma_L, \gamma_S$ and $\Delta m$ yields a bound on the CP-violating overlap $\delta = \braket{K_L}{K_S}$, which is similar to, but weaker than, the known unitarity bound. A similar requirement on $|\vec{\zeta}(t)|$ yields a new bound, $\delta^2 < {1/2} (\frac{\Delta \gamma}{\Delta m}) \sinh (\frac{3\pi}{4} \frac{\Delta \gamma}{\Delta m})$ which is particularly effective in limiting the CP-violating overlap in the $B^0$-$\bar{B^0}$ system. We obtain the Stokes parameter $\ |
6409692c-0f52-46cd-82e7-7655884b09fe | 6409692c-0f52-46cd-82e7-7655884b09fe | 6409692c-0f52-46cd-82e7-7655884b09fe | human | null | null | none | abstracts | Fluctuations of the partial filling factors in competitive RSA from
binary mixtures | null | Competitive random sequential adsorption on a line from a binary mix of incident particles is studied using both an analytic recursive approach and Monte Carlo simulations. We find a strong correlation between the small and the large particle distributions so that while both partial contributions to the fill factor fluctuate widely, the variance of the total fill factor remains relatively small. The variances of partial contributions themselves are quite different between the smaller and the larger particles, with the larger particle distribution being more correlated. The disparity in fluctuations of partial fill factors increases with the particle size ratio. The additional variance in the partial contribution of smaller particle originates from the fluctuations in the size of gaps between larger particles. We discuss the implications of our results to semiconductor high-energy gamma detectors where the detector energy resolution is controlled by correlations in the cascade energy |
71c0577f-e66a-421d-9b11-5be236d6fd48 | 71c0577f-e66a-421d-9b11-5be236d6fd48 | 71c0577f-e66a-421d-9b11-5be236d6fd48 | human | null | null | none | abstracts | Infrared High-Resolution Spectroscopy of Post-AGB Circumstellar Disks.
I. HR 4049 - The Winnowing Flow Observed? | null | High-resolution infrared spectroscopy in the 2.3-4.6 micron region is reported for the peculiar A supergiant, single-lined spectroscopic binary HR 4049. Lines from the CO fundamental and first overtone, OH fundamental, and several H2O vibration-rotation transitions have been observed in the near-infrared spectrum. The spectrum of HR 4049 appears principally in emission through the 3 and 4.6 micron region and in absorption in the 2 micron region. The 4.6 micron spectrum shows a rich 'forest' of emission lines. All the spectral lines observed in the 2.3-4.6 micron spectrum are shown to be circumbinary in origin. The presence of OH and H2O lines confirm the oxygen-rich nature of the circumbinary gas which is in contrast to the previously detected carbon-rich material. The emission and absorption line profiles show that the circumbinary gas is located in a thin, rotating layer near the dust disk. The properties of the dust and gas circumbinary disk and the spectroscopic orbit yield masse |
9cab79c5-8cee-4e16-802a-1e3476d2c799 | 9cab79c5-8cee-4e16-802a-1e3476d2c799 | 9cab79c5-8cee-4e16-802a-1e3476d2c799 | human | null | null | none | abstracts | Cooling and heating by adiabatic magnetization in the
Ni$_{50}$Mn$_{34}$In$_{16}$ magnetic shape memory alloy | null | We report on measurements of the adiabatic temperature change in the inverse magnetocaloric Ni$_{50}$Mn$_{34}$In$_{16}$ alloy. It is shown that this alloy heats up with the application of a magnetic field around the Curie point due to the conventional magnetocaloric effect. In contrast, the inverse magnetocaloric effect associated with the martensitic transition results in the unusual decrease of temperature by adiabatic magnetization. We also provide magnetization and specific heat data which enable to compare the measured temperature changes to the values indirectly computed from thermodynamic relationships. Good agreement is obtained for the conventional effect at the second-order paramagnetic-ferromagnetic phase transition. However, at the first order structural transition the measured values at high fields are lower than the computed ones. Irreversible thermodynamics arguments are given to show that such a discrepancy is due to the irreversibility of the first-order martensitic |
e3836b1c-058f-4fff-9a1d-8fafdcb42eab | e3836b1c-058f-4fff-9a1d-8fafdcb42eab | e3836b1c-058f-4fff-9a1d-8fafdcb42eab | human | null | null | none | abstracts | Outflow and Infall in a Sample of Massive Star Forming Regions | null | We present single pointing observations of SiO, HCO$^+$ and H$^{13}$CO$^+$ from the James Clerk Maxwell Telescope towards 23 massive star forming regions previously known to contain molecular outflows and ultracompact HII regions. We detected SiO towards 14 sources and suggest that the non-detections in the other nine sources could be due to those outflows being older and without ongoing shocks to replenish the SiO. We serendipitously detected SO$_2$ towards 17 sources in the same tuning as HCO$^+$. We detected HCO$^+$ towards all sources, and suggest that it is tracing infall in nine cases. For seven infall candidates, we estimate mass infall rates between 1$\times10^{-2}$ and 2$\times10^{-5}$ M$_{\odot}$ yr$^{-1}$. Seven sources show both SiO detections (young outflows) and HCO$^+$ infall signatures. We also find that the abundance of H$^{13}$CO$^+$ tends to increase along with the abundance of SiO in sources for which we could determine abundances. We discuss these results with re |
1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | 1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | 1c8b00af-a5b7-45d5-b41d-4fb541bb6ad9 | human | null | null | none | abstracts | A Rational Approach to Resonance Saturation in large-Nc QCD | null | We point out that resonance saturation in QCD can be understood in the large-Nc limit from the mathematical theory of Pade Approximants to meromorphic functions. These approximants are rational functions which encompass any saturation with a finite number of resonances as a particular example, explaining several results which have appeared in the literature. We review the main properties of Pade Approximants with the help of a toy model for the <VV-AA> two-point correlator, paying particular attention to the relationship among the Chiral Expansion, the Operator Product Expansion and the resonance spectrum. In passing, we also comment on an old proposal made by Migdal in 1977 which has recently attracted much attention in the context of AdS/QCD models. Finally, we apply the simplest Pade Approximant to the <VV-AA> correlator in the real case of QCD. The general conclusion is that a rational approximant may reliably describe a Green's function in the Euclidean, but the same is not true |
e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | e530abe2-5e1c-433f-9fa7-798cd2dd81d4 | human | null | null | none | abstracts | Coupling between magnetic ordering and structural instabilities in
perovskite biferroics: A first-principles study | null | We use first-principles density functional theory-based calculations to investigate structural instabilities in the high symmetry cubic perovskite structure of rare-earth (R $=$ La, Y, Lu) and Bi-based biferroic chromites, focusing on $\Gamma$ and $R$ point phonons of states with para-, ferro-, and antiferromagnetic ordering. We find that (a) the structure with G-type antiferromagnetic ordering is most stable, (b) the most dominant structural instabilities in these oxides are the ones associated with rotations of oxygen octahedra, and (c) structural instabilities involving changes in Cr-O-Cr bond angle depend sensitively on the changes in magnetic ordering. The dependence of structural instabilities on magnetic ordering can be understood in terms of how super-exchange interactions depend on the Cr-O-Cr bond angles and Cr-O bond lengths. We demonstrate how adequate buckling of Cr-O-Cr chains can favour ferromagnetism. Born effective charges (BEC) calculated using the Berry phase expre |
684e919e-e822-4fb0-9812-6da0f07fe9dc | 684e919e-e822-4fb0-9812-6da0f07fe9dc | 684e919e-e822-4fb0-9812-6da0f07fe9dc | human | null | null | none | abstracts | LNRF-velocity hump-induced oscillations of a Keplerian disc orbiting
near-extreme Kerr black hole: A possible explanation of high-frequency QPOs
in GRS 1915+105 | null | At least four high-frequency quasiperiodic oscillations (QPOs) at frequencies 41Hz, 67Hz, 113Hz, and 167Hz were reported in a binary system GRS 1915+105 hosting near-extreme Kerr black hole with a dimensionless spin a>0.98. We use the idea of oscillations induced by the hump of the orbital velocity profile (related to locally non-rotating frames - LNRF) in discs orbiting near-extreme Kerr black holes, which are characterized by a "humpy frequency" f_h, that could excite the radial and vertical epicyclic oscillations with frequencies f_r, f_v. Due to non-linear resonant phenomena the combinational frequencies are allowed as well. Assuming mass M=14.8M_sun and spin a=0.9998 for the GRS 1915+105 Kerr black hole, the model predicts frequencies f_h=41Hz, f_r=67Hz, (f_h+f_r)=108Hz, (f_v-f_r)=170Hz corresponding quite well to the observed ones. For black-hole parameters being in good agreement with those given observationally, the forced resonant phenomena in non-linear oscillations, excite |
c82c9488-c871-4240-a379-0d4ce546dbbb | c82c9488-c871-4240-a379-0d4ce546dbbb | c82c9488-c871-4240-a379-0d4ce546dbbb | human | null | null | none | abstracts | The Measurement Calculus | null | Measurement-based quantum computation has emerged from the physics community as a new approach to quantum computation where the notion of measurement is the main driving force of computation. This is in contrast with the more traditional circuit model which is based on unitary operations. Among measurement-based quantum computation methods, the recently introduced one-way quantum computer stands out as fundamental. We develop a rigorous mathematical model underlying the one-way quantum computer and present a concrete syntax and operational semantics for programs, which we call patterns, and an algebra of these patterns derived from a denotational semantics. More importantly, we present a calculus for reasoning locally and compositionally about these patterns. We present a rewrite theory and prove a general standardization theorem which allows all patterns to be put in a semantically equivalent standard form. Standardization has far-reaching consequences: a new physical architectu |
b0c50edf-cf99-4c7b-a773-b93d9cf488f1 | b0c50edf-cf99-4c7b-a773-b93d9cf488f1 | b0c50edf-cf99-4c7b-a773-b93d9cf488f1 | human | null | null | none | abstracts | Parametric Learning and Monte Carlo Optimization | null | This paper uncovers and explores the close relationship between Monte Carlo Optimization of a parametrized integral (MCO), Parametric machine-Learning (PL), and `blackbox' or `oracle'-based optimization (BO). We make four contributions. First, we prove that MCO is mathematically identical to a broad class of PL problems. This identity potentially provides a new application domain for all broadly applicable PL techniques: MCO. Second, we introduce immediate sampling, a new version of the Probability Collectives (PC) algorithm for blackbox optimization. Immediate sampling transforms the original BO problem into an MCO problem. Accordingly, by combining these first two contributions, we can apply all PL techniques to BO. In our third contribution we validate this way of improving BO by demonstrating that cross-validation and bagging improve immediate sampling. Finally, conventional MC and MCO procedures ignore the relationship between the sample point locations and the associated values |
fe38de29-96d2-4dfb-aacd-36d49ec735be | fe38de29-96d2-4dfb-aacd-36d49ec735be | fe38de29-96d2-4dfb-aacd-36d49ec735be | human | null | null | none | abstracts | Realizable Hamiltonians for Universal Adiabatic Quantum Computers | null | It has been established that local lattice spin Hamiltonians can be used for universal adiabatic quantum computation. However, the 2-local model Hamiltonians used in these proofs are general and hence do not limit the types of interactions required between spins. To address this concern, the present paper provides two simple model Hamiltonians that are of practical interest to experimentalists working towards the realization of a universal adiabatic quantum computer. The model Hamiltonians presented are the simplest known QMA-complete 2-local Hamiltonians. The 2-local Ising model with 1-local transverse field which has been realized using an array of technologies, is perhaps the simplest quantum spin model but is unlikely to be universal for adiabatic quantum computation. We demonstrate that this model can be rendered universal and QMA-complete by adding a tunable 2-local transverse XX coupling. We also show the universality and QMA-completeness of spin models with only 1-local Z and |
6b15d7af-e499-46a3-aaa4-512fc0150b68 | 6b15d7af-e499-46a3-aaa4-512fc0150b68 | 6b15d7af-e499-46a3-aaa4-512fc0150b68 | human | null | null | none | abstracts | Photometry of the SW Sex-type nova-like BH Lyncis in high state | null | Aims: We present a photometric study of the deeply eclipsing SW Sex-type nova-like cataclysmic variable star BH Lyn Methods: Time-resolved V-band CCD photometry was obtained for seven nights between 1999 and 2004. Results: We determined 11 new eclipse timings of BH Lyn and derived a refined orbital ephemeris with an orbital period of 0.155875577(14) day. During the observations, BH Lyn was in high-state with V~15.5 mag. The star presents ~1.5 mag deep eclipses with mean full-width at half-flux of 0.0683(+/-0.0054)P_orb. The eclipse shape is highly variable, even changing form cycle to cycle. This is most likely due to accretion disc surface brightness distribution variations, most probably caused by strong flickering. Time-dependent accretion disc self-occultation or variations of the hot spot(s) intensity are also possible explanations. Negative superhumps with period of ~0.145 day are detected in two long runs in 2000. A possible connection between SW Sex and negative superhu |
10977dce-f8b1-4580-a28c-d2441223a069 | 10977dce-f8b1-4580-a28c-d2441223a069 | 10977dce-f8b1-4580-a28c-d2441223a069 | human | null | null | none | abstracts | Antenna Combining for the MIMO Downlink Channel | null | A multiple antenna downlink channel where limited channel feedback is available to the transmitter is considered. In a vector downlink channel (single antenna at each receiver), the transmit antenna array can be used to transmit separate data streams to multiple receivers only if the transmitter has very accurate channel knowledge, i.e., if there is high-rate channel feedback from each receiver. In this work it is shown that channel feedback requirements can be significantly reduced if each receiver has a small number of antennas and appropriately combines its antenna outputs. A combining method that minimizes channel quantization error at each receiver, and thereby minimizes multi-user interference, is proposed and analyzed. This technique is shown to outperform traditional techniques such as maximum-ratio combining because minimization of interference power is more critical than maximization of signal power in the multiple antenna downlink. Analysis is provided to quantify the feed |
7ad6c049-53e5-4e0b-a415-126704fb70f1 | 7ad6c049-53e5-4e0b-a415-126704fb70f1 | 7ad6c049-53e5-4e0b-a415-126704fb70f1 | human | null | null | none | abstracts | Hitting probabilities for systems of non-linear stochastic heat
equations with multiplicative noise | null | We consider a system of d non-linear stochastic heat equations in spatial dimension 1 driven by d-dimensional space-time white noise. The non-linearities appear both as additive drift terms and as multipliers of the noise. Using techniques of Malliavin calculus, we establish upper and lower bounds on the one-point density of the solution u(t,x), and upper bounds of Gaussian-type on the two-point density of (u(s,y),u(t,x)). In particular, this estimate quantifies how this density degenerates as (s,y) converges to (t,x). From these results, we deduce upper and lower bounds on hitting probabilities of the process {u(t,x)}_{t \in \mathbb{R}_+, x \in [0,1]}, in terms of respectively Hausdorff measure and Newtonian capacity. These estimates make it possible to show that points are polar when d >6 and are not polar when d<6. We also show that the Hausdorff dimension of the range of the process is 6 when d>6, and give analogous results for the processes t \mapsto u(t,x) and x \mapsto u(t,x). |
5ae899c0-ca50-43d2-bc73-db82e3606664 | 5ae899c0-ca50-43d2-bc73-db82e3606664 | 5ae899c0-ca50-43d2-bc73-db82e3606664 | human | null | null | none | abstracts | Physisorption of Nucleobases on Graphene | null | We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density functional theory framework, with additional calculations utilizing Hartree--Fock plus second-order Moeller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G > T ~ C ~ A > U, with the equilibrium configuration being very similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step towards a first-principles understanding of how the base sequence of DNA can aff |
f54433d5-de46-485f-bef1-5877e65d92c6 | f54433d5-de46-485f-bef1-5877e65d92c6 | f54433d5-de46-485f-bef1-5877e65d92c6 | human | null | null | none | abstracts | The Haunted Halos of Andromeda and Triangulum: A panorama of galaxy
formation in action | null | We present a deep photometric survey of M31, conducted with the CFHT and INT, covering the inner 50 kpc of the galaxy, the Southern quadrant out to 150 kpc, and extending to M33. This is the first systematic panoramic study of this very outermost region of galaxies. We detect several streams and other large-scale structures, and two new dwarf galaxies: And XV and XVI. The discovery of substructure on the minor axis, together with the fact that the light profile between 0.5 < R < 1.3 follows the exponential ``extended disk'', is particularly important in shedding light on the mixed and sometimes conflicting results reported in previous studies. Underlying the substructures lies a faint, metal-poor, smooth and extremely extended halo, reaching out to at least 150 kpc. The smooth halo component in M31 has a profile that can be fit with a Hernquist model of immense scale radius ~55 kpc, almost a factor of 4 larger than theoretical predictions. Alternatively a power-law with exponent -1.9 |
1d9cebf5-5c36-4945-90df-48249b1f5491 | 1d9cebf5-5c36-4945-90df-48249b1f5491 | 1d9cebf5-5c36-4945-90df-48249b1f5491 | human | null | null | none | abstracts | Supersymmetry versus Gauge Symmetry on the Heterotic Landscape | null | One of the goals of the landscape program in string theory is to extract information about the space of string vacua in the form of statistical correlations between phenomenological features that are otherwise uncorrelated in field theory. Such correlations would thus represent predictions of string theory that hold independently of a vacuum-selection principle. In this paper, we study statistical correlations between two features which are likely to be central to any potential description of nature at high energy scales: gauge symmetries and spacetime supersymmetry. We analyze correlations between these two kinds of symmetry within the context of perturbative heterotic string vacua, and find a number of striking features. We find, for example, that the degree of spacetime supersymmetry is strongly correlated with the probabilities of realizing certain gauge groups, with unbroken supersymmetry at the string scale tending to favor gauge-group factors with larger rank. We also find tha |
42bdf3bd-5dad-436a-be0c-e326dc7b3537 | 42bdf3bd-5dad-436a-be0c-e326dc7b3537 | 42bdf3bd-5dad-436a-be0c-e326dc7b3537 | human | null | null | none | abstracts | Instabilities in the time-dependent neutrino disc in Gamma-Ray Bursts | null | We investigate the properties and evolution of accretion tori formed after the coalescence of two compact objects. At these extreme densities and temperatures, the accreting torus is cooled mainly by neutrino emission produced primarily by electron and positron capture on nucleons (beta reactions). We solve for the disc structure and its time evolution by introducing a detailed treatment of the equation of state which includes photodisintegration of helium, the condition of beta-equilibrium, and neutrino opacities. We self-consistently calculate the chemical equilibrium in the gas consisting of helium, free protons, neutrons and electron-positron pairs and compute the chemical potentials of the species, as well as the electron fraction throughout the disc. We find that, for sufficiently large accretion rates (> 10 solar masses per second), the inner regions of the disk become opaque and develop a viscous and thermal instability. The identification of this instability might be relevan |