Temperature and Polarization Patterns in Anisotropic Cosmologies

We study the coherent temperature and polarization patterns produced in homogeneous but anisotropic cosmological models. We show results for all Bianchi types with a Friedman-Robertson-Walker limit (i.e. Types I, V, VII$_{0}$, VII$_{h}$ and IX) to illustrate the range of possible behaviour. We discuss the role of spatial curvature, shear and rotation in the geodesic equations for each model and establish some basic results concerning the symmetries of the patterns produced. We also give examples of the time-evolution of these patterns in terms of the Stokes parameters $I$, $Q$ and $U$.Comment: 24 pages, 7 Figures, submitted to JCAP. Revised version: numerous references added, text rewritten, and errors corrected

Idling Magnetic White Dwarf in the Synchronizing Polar BY Cam. The Noah-2 Project

Results of a multi-color study of the variability of the magnetic cataclysmic variable BY Cam are presented. The observations were obtained at the Korean 1.8m and Ukrainian 2.6m, 1.2m and 38-cm telescopes in 2003-2005, 56 observational runs cover 189 hours. The variations of the mean brightness in different colors are correlated with a slope dR/dV=1.29(4), where the number in brackets denotes the error estimates in the last digits. For individual runs, this slope is much smaller ranging from 0.98(3) to 1.24(3), with a mean value of 1.11(1). Near the maximum, the slope becomes smaller for some nights, indicating more blue spectral energy distribution, whereas the night-to-night variability has an infrared character. For the simultaneous UBVRI photometry, the slopes increase with wavelength from dU/dR=0.23(1) to dI/dR=1.18(1). Such wavelength dependence is opposite to that observed in non-magnetic cataclysmic variables, in an agreement to the model of cyclotron emission. The principal component analysis shows two (with a third at the limit of detection) components of variablitity with different spectral energy distribution, which possibly correspond to different regions of emission. The scalegram analysis shows a highest peak corresponding to the 200-min spin variability, its quarter and to the 30-min and 8-min QPOs. The amplitudes of all these components are dependent on wavelength and luminosity state. The light curves were fitted by a statistically optimal trigonometrical polynomial (up to 4-th order) to take into account a 4-hump structure. The dependences of these parameters on the phase of the beat period and on mean brightness are discussed. The amplitude of spin variations increases with an increasing wavelength and with decreasing brightnessComment: 30pages, 11figures, accepted in Cent.Eur.J.Phy

Ignition conditions for inertial confinement fusion targets with a nuclear spin-polarized DT fuel

The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium?tritium it has been theoretically predicted that the nuclear fusion cross-section could be increased by a factor d = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as d-0.6 and d-0.4 respectively, while the maximum achievable energy gain scales as d0.9

Self-similar plasma expansion of a limited mass into vacuum

A new self-similar solution is presented which describes non-relativistic expansion of a finite plasma mass into vacuum with a full account of charge separation effects. The solution exists only when the ratio ${\rm \Lambda} =$ R/${\lambda}_{\rm D}$ of the plasma scale length R to the Debye length ${\lambda}_{\rm D}$ is invariant, i.e. under the condition T$_{\rm e}$ $\propto$ [ n$_{\rm e}$(t)] $^{1 - 2 /\nu}$, where ${\rm \nu} = 1$, 2, and 3 corresponds, respectively, to the planar, cylindrical, and spherical geometries. For ${\rm \Lambda} \gg 1$ the position of the ion front and the maximum energy E$_{\rm i,max }$ of accelerated ions are calculated analytically: in particular, for ${\rm \nu} =3$ one finds E$_{\rm i,max}=$ 2ZT$_{\rm e0}$W(${\rm \Lambda} ^{2}$/2), where T$_{\rm e0}$ is the initial electron temperature, Z is the ion charge, and W is the Lambert W-function. It is argued that, when properly formulated, the results for E$_{\rm i,max}$ can be applied more generally than the self-similar solution itself

Asymptotic Scaling Laws for Imploding Thin Fluid Shells

Scaling laws governing implosions of thin shells in converging flows are established by analyzing the implosion trajectories in the A, M≫ parametric plane, where A is the in-flight aspect ratio, and M is the implosion Mach number. Three asymptotic branches, corresponding to three implosion phases, are identified for each trajectory in the limit of A, M≫1. It is shown that there exists a critical value γcr = 1 + 2/ν (ν= 1, 2 for, respectively, cylindrical and spherical flows) of the adiabatic index gamma, which separates two qualitatively different patterns of the density buildup in the last phase of implosion. The scaling of the stagnation density ρs and pressure Ps with the peak value M0 of the Mach number is obtained. ©2002 The American Physical Societ

Reflection and reprocessing of X-ray source radiation by the atmosphere of the normal star in a binary system

Reflection and reprocessing of X-ray source radiation by the atmosphere of the normal star in a binary syste

Generalized van der Waals equation of state for in-line use in hydrodynamic codes

Abstract: Basic physical and mathematical properties of one of the simplest generalizations of the van der Waals equation of state (EOS), where the power exponent n in the attractive term is treated as a free parameter, are investigated. The main focus is on the parameter range around the gas-liquid phase transition, and on the possibility of in-line use of the equilibrium EOS branch (based on the Maxwell construction in the phase coexistence region) in one-dimensional (1D) hydrodynamic simulations. Conditions are elucidated for emergence of such flow structures as a 'rarefaction shock' and a 'binodal shelf' in rarefaction waves by unloading of compressed matter into vacuum. The quality of numerical modeling of such structures is illustrated with the 1D Lagrangian code DEIRA.Note: Research direction:Theoretical and applied problems of mechanic