K3 surfaces of finite height over finite fields

Arithmetic of K3 surfaces defined over finite fields is investigated. In particular, we show that any K3 surface of finite height over a finite field k of characteristic p > 3 has a quasi-canonical lifting to characteristic 0, and that for any such lifting, the endormorphism algebra of the transcendental cycles, as a Hodge module, is a CM field. The Tate conjecture for the product of certain two K3 surfaces is also proved. We illustrate by examples how to determine explicitly the formal Brauer group associated to a K3 surface over k. Examples discussed here are all of hypergeometric type.Comment: Cor.3.4 added, typos corrected, to appear in J. Math. Kyoto Uni

Supernova 2014J at maximum light

We present UBVRI photometry of the supernova 2014J in M82, obtained in the period from January 24 until March 3, 2014, as well as two spectra, taken on February 4 and March 5. We derive dates and magnitudes of maximum light in the UBVRI bands, the light curve parameters Delta m(15) and expansion velocities of the prominent absorption lines. We discuss colour evolution, extinction and maximum luminosity of SN 2014J.Comment: 10 pages, 4 figures, submitted to Contrib. Astron. Obs. Skalnate Ples

Intrinsic detection efficiency of superconducting single photon detector in the modified hot spot model

We theoretically study the dependence of the intrinsic detection efficiency (IDE) of superconducting single photon detector on the applied current $I$ and magnetic field $H$. We find that the current, at which the resistive state appears in the superconducting film, depends on the position of the hot spot (region with suppressed superconductivity around the place where the photon has been absorbed) with respect to the edges of the film. It provides inevitable smooth dependence IDE(I) when IDE $\sim 0.05-1$ even for homogenous straight superconducting film and in the absence of fluctuations. When IDE $\lesssim 0.05$ much sharper current dependence comes from the fluctuation assisted vortex entry to the hot spot located near the edge of the film. We find that weak magnetic field strongly affects IDE when the photon detection is connected with fluctuation assisted vortex entry (IDE$\ll 1$) and it weakly affects IDE when the photon detection is connected with the current induced vortex entry to the hot spot or nucleation of the vortex-antivortex pair inside the hot spot (IDE$\sim 0.05-1$).Comment: 10 pages, 12 figure

Water-like Anomalies of Core-Softened Fluids: Dependence on the Trajectories in (PρTP\rho T) Space

In the present article we carry out a molecular dynamics study of the core-softened system and show that the existence of the water-like anomalies in this system depends on the trajectory in $P-\rho-T$ space along which the behavior of the system is studied. For example, diffusion and structural anomalies are visible along isotherms, but disappears along the isochores and isobars, while density anomaly exists along isochors. We analyze the applicability of the Rosenfeld entropy scaling relations to this system in the regions with the water-like anomalies. It is shown that the validity of the of Rosenfeld scaling relation for the diffusion coefficient also depends on the trajectory in the $P-\rho-T$ space along which the kinetic coefficients and the excess entropy are calculated.Comment: 10 pages, 10 Fig

Non-Equilibrium 2PI Potential and Its Possible Application to Evaluation of Bulk Viscosity

Within non-equilibrium Green's function technique on the real-time contour and the two-particle-irreducable (2PI) $\Phi$-functional method, a non-equilibrium potential is introduced. It naturally generalizes the conventional thermodynamic potential with which it coincides in thermal equilibrium. Variations of the non-equilibrium potential over respective parameters result in the same quantities as those of the thermodynamic potential but in arbitrary non-equilibrium. In particular, for slightly non-equilibrium inhomogeneous configurations a variation of the non-equilibrium potential over volume is associated with the trace of the non-equilibrium stress tensor. The latter is related to the bulk viscosity. This provides a novel way for evaluation of the bulk viscosity.Comment: 16 pages, references added. arXiv admin note: substantial text overlap with arXiv:hep-ph/980735

Optical theorem for Aharonov-Bohm scattering

Quantum-mechanical scattering off a magnetic vortex is considered, and the optical theorem is derived. The vortex core is assumed to be impermeable to scattered particles, and its transverse size is taken into account. We show that the scattering Aharonov-Bohm effect is independent of the choice of boundary conditions from the variety of the Robin ones. The behaviour of the scattering amplitude in the forward direction is analyzed, and the persistence of the Fraunhofer diffraction in the short-wavelength limit is shown to be crucial for maintaining the optical theorem in the quasiclassical limit.Comment: 22 page

Possible phase transition in liquid Cesium at ambient pressure

We report a molecular dynamics study of liquid cesium at ambient pressure intended to check the possibility of liquid-liquid phase transformation at $T=590$ K. We find the presence of small kinks on thermodynamic characteristics of the system, but no phase transition

Gravimagnetic shock waves in the anisotropic plasma

The relativistic magnetohydrodynamic equations for the anisotropic magnetoactive plasma are obtained and accurately integrated in the plane gravitational wave metrics. The dependence of the induction mechanism of the gravimagnetic shock waves on the degree of the magnetoactive plasma anisotropy is analyzed.Comment: 11 pages, 7 reference

Silica-Like Sequence of Anomalies in Core-Softened Systems

In this paper we present a simulation study of density, structural and diffusion anomalies in core-softened system introduced in our previous publications. It is well-known, that with appropriate parametrization, core-softened systems are remarkable model liquids that exhibit anomalous properties observed in tetrahedral liquids such as silica and water. It is widely believed that core-softened potentials demonstrate the water-like sequence of anomalies. We show that with increasing the depth of the attractive part of the potential the order of the region of anomalous diffusion and the regions of density and structural anomalies is inverted and have the silica-like sequence. We also show that the slope of the Widom line is negative like in water.Comment: 5 pages, 4 figures. arXiv admin note: text overlap with arXiv:1109.164

Gamma-ray Bursts, Type Ib/c Supernovae and Star-forming Sites in Host Galaxies

The data on the location of gamma-ray bursts (GRBs) relative to their host galaxies are used to derive the distribution of surface density of GRBs along the galaxy radius. It is shown that the gradient of GRB surface density changes abruptly near the half-light radius. In the central parts of galaxies the distribution of GRBs resembles closely the luminosity distribution, while in the outer parts the galactic surface brightness falls much steeper than the GRBs density. The radial distribution of type Ib/c supernovae is investigated on the basis of enlarged statistics. It is shown that SNe Ib/c do not differ significantly from other types of supernovae and their distribution is more similar to the one for recent star formation sites than that of GRBs. In spite of the poor statistics of GRBs, the difference in the distributions of active star formation regions and GRBs appears to be significant. We get the Kolmogorov-Smirnov probability P_ks of only 4% that GRBs and star-forming sites belong to the same distribution. The correlation of GRBs with the distribution of dark matter in the outer parts of galaxies is not excluded.Comment: 10 pages, 2 figures, presented at Coll. "Strongest Explosions in the Universe" on 17th Nov., 2000, SAI, Mosco