119384628
STATIONARY VACUUM HYPER-CYLINDRICAL SOLUTION IN 4 + 1 DIMENSIONS
We find a (4+1)-dimensional stationary vacuum hyper-cylindrical solution which is spherically symmetric in three dimensions and invariant under the translation along the fifth coordinate. The solution is characterized by three parameters, mass, tension, and conserved momentum along the fifth coordinate. The metric is locally equivalent to the known static solution. We briefly discuss its physical properties.
15236719
Global and local D-vortices
Codimension-two objects on a system of brane-antibrane are studied in the context of Born-Infeld type effective field theory with a complex tachyon and U(1) × U(1) gauge fields. When the radial electric field is turned on in D2 ¯ D2, we find static regular global and local D-vortex solutions which could be candidates of straight cosmic D-strings in a superstring theory. A natural extension to DF-strings is briefly discussed.
119451627
Dark energy, inflation and the cosmic coincidence problem
Abstract We show that holographic dark energy could explain why the current dark energy density is so small, if there was an inflation with a sufficient expansion in the early universe. It is also suggested that an inflation with the number of e-folds N ≃ 65 may solve the cosmic coincidence problem in this context. Assuming the inflation and the power-law acceleration phase today we obtain approximate formulas for the event horizon size of the universe and dark energy density as functions of time. A simple numerical study exploiting the formula well reproduces the observed evolution of dark energy. This nontrivial match between the theory and the observational data supports both inflation and holographic dark energy models.
119306084
An efficient representation of Euclidean gravity I
A bstractWe explore how the topology of spacetime fabric is encoded into the local structure of Riemannian metrics using the gauge theory formulation of Euclidean gravity. In part I, we provide a rigorous mathematical foundation to prove that a general Einstein manifold arises as the sum of SU(2)L Yang-Mills instantons and SU(2)R anti-instantons where SU(2)L and SU(2)R are normal subgroups of the four-dimensional Lorentz group Spin(4) = SU(2)L × SU(2)R. Our proof relies only on the general properties in four dimensions: The Lorentz group Spin(4) is isomorphic to SU(2)L × SU(2)R and the six-dimensional vector space Λ2T∗M of two-forms splits canonically into the sum of three-dimensional vector spaces of self-dual and anti-self-dual two-forms, i.e., $ {\Lambda^2}{T^{ * }}M = \Lambda_{ + }^2 \oplus \Lambda_{ - }^2 $. Consolidating these two, it turns out that the splitting of Spin(4) is deeply correlated with the decomposition of two-forms on four-manifold which occupies a central position in the theory of four-manifolds.
118255950
Classical stability of black D3-branes
We have investigated the classical stability of charged black D3-branes in the type-IIB supergravity under small perturbations. For s-wave perturbations it turns out that black D3-branes are unstable when they have small charge density. As the charge density increases for given mass density, however, the instability decreases down to zero at a certain finite value of the charge density, and then black D3-branes become stable all the way down to the extremal point. It has also been shown that such critical value at which its stability behavior changes agrees very well with the predicted one by the thermodynamic stability behavior of the corresponding black hole system through the Gubser-Mitra conjecture. Unstable mode solutions we found involve non-vanishing fluctuations of the self-dual five-form field strength. Some implications of our results are also discussed.
119196611
Extraordinary vacuum black string solutions
In addition to the boosted static solution there are two other classes of stationary stringlike solutions of the vacuum Einstein equation in (4+1) dimensions. Each class is characterized by three parameters of mass, tension, and momentum flow along the fifth coordinate. We analyze the metric properties of one of the two classes, which was previously assumed to be naked singular, and show that the solution spectrum contains black string and wormhole in addition to the known naked singularity as the momentum flow to mass ratio increases. Interestingly, there does not exist new zero momentum solution in these cases.
119233494
Improved determination of color-singlet nonrelativistic QCD matrix elements for S -wave charmonium
We present a new computation of S-wave color-singlet nonrelativistic QCD matrix elements for the J/{psi} and the {eta}{sub c}. We compute the matrix elements of leading order in the heavy-quark velocity v and the matrix elements of relative order v{sup 2}. Our computation is based on the electromagnetic decay rates of the J/{psi} and the {eta}{sub c} and on a potential model that employs the Cornell potential. We include relativistic corrections to the electromagnetic decay rates, resumming a class of corrections to all orders in v, and find that they significantly increase the values of the matrix elements of leading order in v. This increase could have important implications for theoretical predictions for a number of quarkonium decay and production processes. The values that we find for the matrix elements of relative order v{sup 2} are somewhat smaller than the values that one obtains from estimates that are based on the velocity-scaling rules of nonrelativistic QCD.
113405504
He I D3 Observations of the 1984 May 22 M6.3 Solar Flare
The He I D3 line has a unique response to a flare impact on the low solar atmosphere and can be a powerful diagnostic tool for energy transport processes. Using images obtained from the recently digitized films of the Big Bear Solar Observatory, we report D3 observations of the M6.3 flare on 1984 May 22, which occurred in an active region with a circular magnetic polarity inversion line (PIL). The impulsive phase of the flare starts with a main elongated source that darkens in D3, inside of which bright emission kernels appear at the time of the initial small peak in hard X-rays (HXRs). These flare cores subsequently evolve into a sharp emission strand lying within the dark halo; this evolution occurs at the same time as the main peak in HXRs, reversing the overall source contrast from ?5% to 5%. The radiated energy in D3 during the main peak is estimated to be about 1030 erg, which is comparable to that carried by nonthermal electrons above 20?keV. Afterward, the flare proceeds along the circular PIL in the counterclockwise direction to form a dark circular ribbon in D3, which apparently mirrors the bright ribbons in H? and He I 10830 ?. All of these ribbons last for over one hour in the late gradual phase. We suggest that the present event resembles the so-called black-light flare that was proposed based on continuum images, and that D3 darkening and brightening features herein may be due to thermal conduction heating and the direct precipitation of high-energy electrons, respectively.
118610109
The Sub-Saturn Mass Transiting Planet HAT-P-12b
We present new photometric data of the transiting planet HAT-P-12b observed in 2011. Our three transit curves are modeled using the JKTEBOP code and adopting the quadratic limb-darkening law. Including our measurements, 18 transit times spanning about 4.2 yr were used to determine the improved ephemeris with a transit epoch of 2,454,187.85560 ± 0.00011 BJD and an orbital period of 3.21305961 ± 0.00000035 days. The physical properties of the star-planet system are computed using empirical calibrations from eclipsing binary stars and stellar evolutionary models, combined with both our transit parameters and previously known spectroscopic results. We found that the absolute dimensions of the host star are M A = 0.73 ± 0.02 M ☉, R A = 0.70 ± 0.01 R ☉, log g A = 4.61 ± 0.02, ρA = 2.10 ± 0.09 ρ☉, and L A = 0.21 ± 0.01 L ☉. The planetary companion has M b = 0.21 ± 0.01 M Jup, R b = 0.94 ± 0.01 R Jup, log g b = 2.77 ± 0.02, ρb = 0.24 ± 0.01 ρJup, and T eq = 960 ± 14 K. Our results agree well with standard models of irradiated gas giants with a core mass of 11.3 M ⊕.
7604114
R-parity violation and semileptonic decays of B-meson
Abstract We investigate the effects of R -parity violation on the semileptonic decays of B -meson in the minimal supersymmetric standard model with explicit R -parity violation and discuss its physical implications. We find that the semileptonic decays of B -meson can be largely affected by R -parity violation.
118338235
Are galaxies extending
Abstract It is suggested that the recently observed size evolution of very massive compact galaxies in the early universe can be explained, if dark matter is in Bose–Einstein condensate. In this model the size of the dark matter halos and galaxies depends on the correlation length of dark matter and, hence, on the expansion of the universe. This theory predicts that the size of the galaxies increases as the Hubble radius of the universe even without merging, which agrees well with the recent observational data.