122,418 research outputs found
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 and
magnetic field . 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 even for homogenous straight
superconducting film and in the absence of fluctuations. When IDE 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) 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).Comment: 10 pages, 12 figure
Water-like Anomalies of Core-Softened Fluids: Dependence on the Trajectories in () 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 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 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) -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
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
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