Relativistic Charge Form Factor of the Deuteron

Relativistic integral representation in terms of experimental neutron-proton scattering phase shifts alone is used to compute the charge form factor of the deuteron $G_{Cd}(Q^2)$. The results of numerical calculations of $|G_{Cd}(Q^2)|$ are presented in the interval of the four-momentum transfers squared $0 \leq Q^2 \leq 35 fm^{-2}$. Zero and the prominent secondary maximum in $|G_{Cd}(Q^2)|$ are the direct consequences of the change of sign in the experimental $^3S_1$- phase shifts. Till the point $Q^2 \simeq 20 fm^{-2}$ the total relativistic correction to $|G_{Cd}(Q^2)|$ is positive and reaches the maximal value of 25% at $Q^2 \simeq 14 fm^{-2}$.Comment: 9 pages, LaTeX, 2 postscript figures, uses wor-sci.sty, epsf.st

Magnetic Radius of the Deuteron

The root-mean square radius of the deuteron magnetic moment distribution, $r_{Md}$, is calculated for several realistic models of the $NN$--interaction. For the Paris potential the result is $r_{Md} = 2.312 \pm 0.010$ fm. The dependence of $r_{Md}$ on the choice of $NN$ model, relativistic effects and meson exchange currents is investigated. The experimental value of $r_{Md}$ is also considered. The necessity of new precise measurements of the deuteron magnetic form factor at low values of $Q^2$ is stressed.Comment: 4 pages, RevTe

Defense and security policies of the Russian Federation

Este artigo descreve as políticas de segurança e defesa da Federação Russa, enfatizando as envolventes externas que condicionam e definem a elencagem das prioridades pelo governo em termos de modernização militar para a próxima décad

Navier-Stokes hydrodynamics of thermal collapse in a freely cooling granular gas

We employ Navier-Stokes granular hydrodynamics to investigate the long-time behavior of clustering instability in a freely cooling dilute granular gas in two dimensions. We find that, in circular containers, the homogeneous cooling state (HCS) of the gas loses its stability via a sub-critical pitchfork bifurcation. There are no time-independent solutions for the gas density in the supercritical region, and we present analytical and numerical evidence that the gas develops thermal collapse unarrested by heat diffusion. To get more insight, we switch to a simpler geometry of a narrow-sector-shaped container. Here the HCS loses its stability via a transcritical bifurcation. For some initial conditions a time-independent inhomogeneous density profile sets in, qualitatively similar to that previously found in a narrow-channel geometry. For other initial conditions, however, the dilute gas develops thermal collapse unarrested by heat diffusion. We determine the dynamic scalings of the flow close to collapse analytically and verify them in hydrodynamic simulations. The results of this work imply that, in dimension higher than one, Navier-Stokes hydrodynamics of a dilute granular gas is prone to finite-time density blowups. This provides a natural explanation to the formation of densely packed clusters of particles in a variety of initially dilute granular flows.Comment: 18 pages, 19 figure

Growth rates of the Weibel and tearing mode instabilities in a relativistic pair plasma

We present an algorithm for solving the linear dispersion relation in an inhomogeneous, magnetised, relativistic plasma. The method is a generalisation of a previously reported algorithm that was limited to the homogeneous case. The extension involves projecting the spatial dependence of the perturbations onto a set of basis functions that satisfy the boundary conditions (spectral Galerkin method). To test this algorithm in the homogeneous case, we derive an analytical expression for the growth rate of the Weibel instability for a relativistic Maxwellian distribution and compare it with the numerical results. In the inhomogeneous case, we present solutions of the dispersion relation for the relativistic tearing mode, making no assumption about the thickness of the current sheet, and check the numerical method against the analytical expression.Comment: Accepted by PPC

Differential Form of the Collision Integral for a Relativistic Plasma

The differential formulation of the Landau-Fokker-Planck collision integral is developed for the case of relativistic electromagnetic interactions.Comment: Plain TeX, 5 page

Ultra-relativistic electrostatic Bernstein waves

A new general form of the dispersion relation for electrostatic Bernstein waves in ultra-relativistic pair plasmas, characterized by a−1 = kBT/(mec2)  1, is derived in this paper. The parameter Sp = aΩ0/ωp, where Ω0 is the rest cyclotron frequency for electrons or positrons and ωp is the electron (or positron) plasma frequency, plays a crucial role in characterizing these waves. In particular, Sp has a restricted range for permitted wave solutions; this range is effectively unlimited for classical plasmas, but is significant for the ultra-relativistic case. The characterization of these waves is applied in particular to the presence of such plasmas in pulsar atmospheres