Rotational kinetics of absorbing dust grains in neutral gas

We study the rotational and translational kinetics of massive particulates (dust grains) absorbing the ambient gas. Equations for microscopic phase densities are deduced resulting in the Fokker-Planck equation for the dust component. It is shown that although there is no stationary distribution, the translational and rotational temperatures of dust tend to certain values, which differ from the temperature of the ambient gas. The influence of the inner structure of grains on rotational kinetics is also discussed.Comment: REVTEX4, 20 pages, 2 figure

Plasma wave instabilities induced by neutrinos

Quantum field theory is applied to study the interaction of an electron plasma with an intense neutrino flux. A connection is established between the field theory results and classical kinetic theory. The dispersion relation and damping rate of the plasma longitudinal waves are derived in the presence of neutrinos. It is shown that Supernova neutrinos are never collimated enough to cause non-linear effects associated with a neutrino resonance. They only induce neutrino Landau damping, linearly proportional to the neutrino flux and $G_{\mathrm{F}}^{2}$.Comment: 18 pages, 3 figures, title and references correcte

On the hadronic contribution to sterile neutrino production

Sterile neutrinos with masses in the keV range are considered to be a viable candidate for warm dark matter. The rate of their production through active-sterile neutrino transitions peaks, however, at temperatures of the order of the QCD scale, which makes it difficult to estimate their relic abundance quantitatively, even if the mass of the sterile neutrino and its mixing angle were known. We derive here a relation, valid to all orders in the strong coupling constant, which expresses the production rate in terms of the spectral function associated with active neutrinos. The latter can in turn be expressed as a certain convolution of the spectral functions related to various mesonic current-current correlation functions, which are being actively studied in other physics contexts. In the naive weak coupling limit, the appropriate Boltzmann equations can be derived from our general formulae.Comment: 28 pages. v2: small clarifications added, published versio

Dynamic screening in solar and stellar nuclear reactions

In the hot, dense plasma of solar and stellar interiors, the Coulomb interaction is screened by the surrounding plasma. Although the standard Salpeter approximation for static screening is widely accepted and used in stellar modeling, the question of dynamic screening has been revisited. In particular, Shaviv and Shaviv apply the techniques of molecular dynamics to the conditions in the solar core in order to numerically determine the dynamic screening effect. By directly calculating the motion of ions and electrons due to Coulomb interactions, they compute the effect of screening without the mean-field assumption inherent in the Salpeter approximation. Here we reproduce their numerical analysis of the screening energy in the plasma of the solar core and conclude that the effects of dynamic screening are relevant and should be included in the treatment of the plasma, especially in the computation of stellar nuclear reaction rates.Comment: Astrophysics and Space Science, Special Issue Solar & Stellar Modelling Corrected sign error. Now consistent with final published versio

Cosmic Rays during BBN as Origin of Lithium Problem

There may be non-thermal cosmic rays during big-bang nucleosynthesis (BBN) epoch (dubbed as BBNCRs). This paper investigated whether such BBNCRs can be the origin of Lithium problem or not. It can be expected that BBNCRs flux will be small in order to keep the success of standard BBN (SBBN). With favorable assumptions on the BBNCR spectrum between 0.09 -- 4 MeV, our numerical calculation showed that extra contributions from BBNCRs can account for the $^7$Li abundance successfully. However $^6$Li abundance is only lifted an order of magnitude, which is still much lower than the observed value. As the deuteron abundance is very sensitive to the spectrum choice of BBNCRs, the allowed parameter space for the spectrum is strictly constrained. We should emphasize that the acceleration mechanism for BBNCRs in the early universe is still an open question. For example, strong turbulent magnetic field is probably the solution to the problem. Whether such a mechanism can provide the required spectrum deserves further studies.Comment: 34 pages, 21 figures, published versio

From Coherent Modes to Turbulence and Granulation of Trapped Gases

The process of exciting the gas of trapped bosons from an equilibrium initial state to strongly nonequilibrium states is described as a procedure of symmetry restoration caused by external perturbations. Initially, the trapped gas is cooled down to such low temperatures, when practically all atoms are in Bose-Einstein condensed state, which implies the broken global gauge symmetry. Excitations are realized either by imposing external alternating fields, modulating the trapping potential and shaking the cloud of trapped atoms, or it can be done by varying atomic interactions by means of Feshbach resonance techniques. Gradually increasing the amount of energy pumped into the system, which is realized either by strengthening the modulation amplitude or by increasing the excitation time, produces a series of nonequilibrium states, with the growing fraction of atoms for which the gauge symmetry is restored. In this way, the initial equilibrium system, with the broken gauge symmetry and all atoms condensed, can be excited to the state, where all atoms are in the normal state, with completely restored gauge symmetry. In this process, the system, starting from the regular superfluid state, passes through the states of vortex superfluid, turbulent superfluid, heterophase granular fluid, to the state of normal chaotic fluid in turbulent regime. Both theoretical and experimental studies are presented.Comment: Latex file, 25 pages, 4 figure

Collective Modes in Neutrino `Beam' Electron-Positron Plasma Interactions

We derive semiclassical neutrino-electron transport equations in the collisionless (Vlasov) limit from the coupled Dirac equations, incorporating the charged and neutral weak current-current as well as electromagnetic interactions. A corresponding linear response theory is derived. In particular, we calculate the response functions for a variety of beam-plasma geometries, which are of interest in a supernova scenario. We apply this to the study of plasmons and to a new class of collective {\it pharon} resonance modes, which are characterized by $\omega < q$. We find that the growth rates of the unstable modes correspond to a strongly temperature ($\propto T_\nu^2T_e^3$) and linearly momentum dependent e-folding length of about $10^{10}$ km under typical conditions for Type II supernovae. This appears to rule out such long-wavelength collective modes as an efficient means of depositing neutrino energy into the plasma sphere.Comment: 27 pages; LaTex. Replaced by published version. - Appendix about neutrino Wigner functions added and main text correspondingly revised. Conclusions unchange

Collective Plasma Corrections to Thermonuclear Reactions Rates in Dense Plasmas

"General kinetic equations for nuclear reaction in dense plasmas are obtaincd. They take into account the first order collective plasma effects. Together wit,h previously known corrections proportional to ZiZj, the product of the charges Zi and Zj of two interacting nuclei, it is shown tha there exist corrections proportional to the squares Z_i^2 and Z_j^2 of the charges. It is shown that the Salpeter\u27s [l] corrcction due to the plasma screening of the interaction potential is at least r/d smaller(r is the nuclei size and d is Debye screening length) than previously thought and is zero in the approximation when the terms of the order r/d are neglectcd. But the correlation effects in the first approximation in the paramter 1/N_d (where N_d is the number of particle in the Debye sphere) give corrections which often coincide with the first order Salpeter\u27s corrections (found by expansion in another small parameter, the ratio of thermal energy to Gamov\u27s energy). The correlation corrections are propto Z_iZ_j, have a different physical meaning than the correctious [l], can have a different sign and are present for reactions where the Salpeter\u27s corrections are zero. Previously in astrophysical applications it was widely used the interpolation formulas between weak and strong Salpeter\u27s screening corrections. Since the correlation correction take placc the previously known Salpeter\u27s corrections and the strong correlation corrections is difficult to describe analytica1ly, the interpolation formulas between the weak and strong correlations cannot be yet found. A new type of corrections are found here which are proportional to the sequare of the charges. They are due to collective change in electrostatic self-encrgy of the plasma system during the nuclear reactions. The latter corrections are found by taking into account the changes of plasma particle fluctuatious by the nuclear reactions. Numerical evaluation of the plasma corrections for the nuclear reactions of thc hydrogen cycle, using the parameters of the present, temperature, density and abundance in the solar interior, are performcd.