119292700
Matter fields near quantum critical point in (2+1)-dimensional U(1) gauge theory
We study chiral phase transition and confinement of matter fields in (2+1)-dimensional U(1) gauge theory of massless Dirac fermions and scalar bosons. The vanishing scalar boson mass, r = 0, defines a quantum critical point between the Higgs phase and the Coulomb phase. We consider only the critical point r = 0 and the Coulomb phase with r > 0. The Dirac fermion acquires a dynamical mass when its flavor is less than certain critical value N c f , which depends quantitatively on the flavor Nb and the scalar boson mass r. When Nf < N c f , the matter fields carrying internal gauge charge are all confined if r 6 0 but are deconfined at the quantum critical point r = 0. The system has distinct low-energy elementary excitations at the critical point r = 0 and in the Coulomb phase with r 6 0. We calculate the specific heat and susceptibility of the system at r = 0 and r 6 0, which can help to detect the quantum critical point and to judge whether dynamical fermion mass generation takes place.
118672243
Topology and criticality in the resonating Affleck-Kennedy-Lieb-Tasaki loop spin liquid states
We exploit a natural Projected Entangled-Pair State (PEPS) representation for the resonating Affleck-Kennedy-Lieb-Tasaki loop (RAL) state. By taking advantage of PEPS-based analytical and numerical methods, we characterize the RAL states on various two-dimensional lattices. On square and honeycomb lattices, these states are critical since the dimer-dimer correlations decay as a power law. On kagome lattice, the RAL state has exponentially decaying correlation functions, supporting the scenario of a gapped spin liquid. We provide further evidence that the RAL state on the kagome lattice is a $\mathbb{Z}_2$ spin liquid, by identifying the four topological sectors and computing the topological entropy. Furthermore, we construct a one-parameter family of PEPS states interpolating between the RAL state and a short-range Resonating Valence Bond state and find a critical point, consistent with the fact that the two states belong to two different phases. We also perform a variational study of the spin-1 kagome Heisenberg model using this one-parameter PEPS.
118857728
Dynamical chiral symmetry breaking in QED{sub 3} at finite density and impurity potential
We study the effects of finite chemical potential and impurity scattering on dynamical fermion mass generation in (2+1)-dimensional quantum electrodynamics. In any realistic systems, these effects usually cannot be neglected. The longitudinal component of the gauge field develops a finite static length produced by chemical potential and impurity scattering, while the transverse component remains long-ranged because of the gauge invariance. Another important consequence of impurity scattering is that the fermions have a finite damping rate, which reduces their lifetime. By solving the Dyson-Schwinger equation for the fermion mass function, it is found that these effects lead to strong suppression of the critical fermion flavor N{sub c} and the dynamical fermion mass in the symmetry broken phase.
612176
System size dependence of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions
We present a systematic study of two-particle angular correlations in p+p, Cu+Cu and Au+Au collisions over a broad range of pseudorapidity and azimuthal angle. The PHOBOS detector has a uniquely large angular coverage for inclusive charged particles, which allows for the study of correlations on both long- and short-range scales. A complex two-dimensional correlation structure emerges which is interpreted in the context of a cluster model. The cluster size and its decay width are extracted from the two-particle pseudorapidity correlation function. The cluster size found in semi-central Cu+Cu and Au+Au collisions is comparable to that found in p+p but a non-trivial increase of cluster size with decreasing centrality is observed. Moreover, the comparison between Cu+Cu and Au+Au systems shows an interesting scaling of the cluster size with the measured fraction of total cross section (which is related to b/2R), suggesting a geometric origin. These results should provide insight into the hadronization stage of the hot and dense medium created in heavy ion collisions.
209999832
Measurements of charge transfer efficiency in a proton-irradiated swept charge device
Charged Coupled Devices (CCDs) have been successfully used in several low energy X-ray astronomical satellites over the past two decades. Their high energy resolution and high spatial resolution make them a perfect tool for low energy astronomy, such as observing the formation of galaxy clusters and the environment around black holes. The Low Energy X-ray Telescope (LE) group is developing a Swept Charge Device (SCD) for the Hard Xray Modulation Telescope (HXMT) satellite. A SCD is a special low energy X-ray CCD, which can be read out a thousand times faster than traditional CCDs, simultaneously keeping excellent energy resolution. A test method for measuring the charge transfer efficiency (CTE) of a prototype SCD has been set up. Studies of the charge transfer inefficiency (CTI) with a proton-irradiated SCD have been performed at a range of operating temperatures. The SCD is irradiated by 3x10(8)cm(-2) 10 MeV protons.
125944692
High-p(T) di-hadron and jet-hadron correlations in p p and PbPb collisions
14441114
OPTICAL AND NEAR-INFRARED OBSERVATIONS OF THE HIGHLY REDDENED, RAPIDLY EXPANDING TYPE Ia SUPERNOVA SN 2006X IN M100
We present extensive optical (UBVRI), near-infrared (JK) light curves and optical spectroscopy of the Type Ia supernova SN 2006X in the nearby galaxy NGC 4321 (M100). Our observations suggest that either SN 2006X has an intrinsically peculiar color evolution or it is highly reddened [E(B − V)host = 1.42 ± 0.04 mag ] with RV = 1.48 ± 0.06, much lower than the canonical value of 3.1 for the average Galactic dust. SN 2006X also has one of the highest expansion velocities ever published for an SN Ia. Compared with the other SNe Ia we analyzed, SN 2006X has a broader light curve in the U band, a more prominent bump/shoulder feature in the V and R bands, a more pronounced secondary maximum in the I and NIR bands, and a remarkably smaller late-time decline rate in the B band. The B − V color evolution shows an obvious deviation from the Lira-Phillips relation at 1-3 months after maximum brightness. At early times, optical spectra of SN 2006X displayed strong, high-velocity features of both intermediate-mass elements (Si, Ca, and S) and iron peak elements, while at late times they showed a relatively blue continuum, consistent with the blue U − B and B − V colors at similar epochs. A light echo and/or the interaction of the SN ejecta and its circumstellar material may provide a plausible explanation for its late-time photometric and spectroscopic behavior. Using the Cepheid distance of M100, we derive a Hubble constant of 72.8 ± 8.2 km s−1 Mpc−1 (statistical) from the normalized dereddened luminosity of SN 2006X. We briefly discuss whether abnormal dust is a universal signature for all SNe Ia and whether the most rapidly expanding objects form a subclass with distinct photometric and spectroscopic properties.
119177216
Lepton Flavor Violating $\tau$ Decays in Two Higgs Doublet Model III
We study the lepton flavor violating processes of $\tau^-\to\mu^-PP$ decays with $PP=K^+K^-,K^0\bar{K}^0,\pi^+\pi^-,\pi^0\pi^0$ in the framework of two Higgs doublet model III by virtue of the Chiral Perturbation Theory. In this model, only three neutral Higgs bosons contribute to these decays. With the current experimental constraints, we show that (a) the contributions of $|\lambda_{uu(dd)}|$ term are very small for these four decays; (b) we get the correlation between $|\lambda_{ss}|$ and $|\lambda_{\tau\mu}|$. For $|\lambda_{\tau\mu}| \sim 10-400$, one has $|\lambda_{ss}|\sim 40-1$; (c) in the existing model parameter space, $Br(\tau^- \to \mu^- K^+K^-)$ could reach the order of ${\cal O}(10^{-8})$, but $Br(\tau \to \mu^- \pi^+\pi^-/\pi^0\pi^0)$ are too small to be observed.
36928210
The nonlinear effects of fringe fields in HLS
The main body of HLS (Hefei Light Source) is an 800 MeV electron storage ring, whose circumference is about 66 m. As a typical small ring, although the sextupole fields for correction of chromaticities are relatively weak, there still exist strong nonlinear fields coming from fringe fields of dipole and quadrupole magnets. In this paper, the effects of fringe fields on chromaticities and tune shifts with amplitude were discussed and calculated for HLS storage ring. Under the low injection energy, the tune shifts with amplitude coming from fringe fields are one of important sources of transverse Landau damping, which is main stabilizing mechanism for HLS ring.
18839902
Possible Recovery of SN 1961V in Hubble Space Telescope Archival Images
SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a "Type V" supernova. However, it has been argued that SN 1961V was not a genuine supernova, but instead the superoutburst of an η Carinae-like luminous blue variable star. In particular, Filippenko et al. used pre-refurbishment Hubble Space Telescope (HST) Wide Field Planetary Camera (WFPC) images and the known radio position of SN 1961V to conclude that the star survived the eruption and is likely coincident with a V ≈ 25.6, V–I ≈ 1.9 mag object. Recently, Stockdale et al. recovered the fading SN 1961V at radio wavelengths and argue that its behavior is similar that of some Type II supernovae. We have analyzed post-refurbishment archival HST WFPC2 data and find that the new radio position is still consistent with the Filippenko et al. object, which has not changed in brightness or color, but is also consistent with an adjacent, fainter (I ≈ 24.3 mag), and very red (V–I > 1.0 mag) object. We suggest that this fainter object could be the survivor of SN 1961V. Forthcoming HST observations may settle this issue.
2138904
Chiral Gravity in Three Dimensions
Three dimensional Einstein gravity with negative cosmological constant ?1/?2 deformed by a gravitational Chern-Simons action with coefficient 1/? is studied in an asymptotically AdS3 spacetime. It is argued to violate unitary or positivity for generic ? due to negative-energy massive gravitons. However at the critical value ?? = 1, the massive gravitons disappear and BTZ black holes all have mass and angular momentum related by ?M = J. The corresponding chiral quantum theory of gravity is conjectured to exist and be dual to a purely right-moving boundary CFT with central charges (cL,?cR) = (0,?3?/G).