相关论文: Non-equilibrium effects on particle freeze-out in …
We investigate the possible effect of the residual annihilations of heavy particles after freeze-out from equilibrium in the early universe. An error in previous work on this subject is pointed out and the correct method of solving the…
We calculate the exact kinetic evolution of cosmic neutrinos until complete decoupling, in the case when a large neutrino asymmetry exists. While not excluded by present observations, this large asymmetry can have relevant cosmological…
Deviations from kinetic equilibrium of massive particles caused by the universe expansion are calculated analytically in the Boltzmann approximation. For the case of an energy independent amplitude of elastic scattering, an exact partial…
We study the effects of modifying the expansions history of the Universe on Dark Matter freezeout. We derived a modified Boltzmann equation for freeze-out for an arbitrary energy density in the early Universe and provide an analytic…
A convenient form of kinetic equation is derived for pair annihilation of heavy stable particles relevant to the dark matter problem in cosmology. The kinetic equation thus derived extends the on-shell Boltzmann equation in a most…
Starting from a Caldeira-Leggett model for the interaction of a system with an environment, Joichi, Matsumoto, and Yoshimura have reconsidered the derivation of the quantum Boltzmann equation. They find an extra term that accounts for the…
Approximate analytical solutions of the Boltzmann equation for particles that are either extremely relativistic or non-relativistic when they decouple from the thermal bath are well established. However, no analytical formula for the relic…
An influence of initial distribution nonequilibrium parameters on thermodynamical equilibrium recovery processes in early Universe under the assumption of elementary particles' scaling of interactions in range of superhigh energies is…
We consider particle oscillations and their damping in second-quantized form. We find that the damping or "decoherence" may be described by a Boltzmann-like collision integral with "non-abelian blocking factors" (fermions). Earlier results…
It has been researched the kinetics of the thermal equilibrium's establishment in an early Universe under the assumption of the recovery of interaction scaling of elementary particles in range of superhigh energies. The case of the thermal…
Small thermodynamic systems exhibit peculiar behavior different from that observed in long-scale systems. Non-equilibrium processes taking place in those systems are strongly influenced by the presence of fluctuations which can be large.…
The annihilation of electron-positron pairs around one second after the big bang distorts the Fermi-Dirac spectrum of neutrino energies. We determine the distortions assuming neutrino mixing with an inverted neutrino-mass hierarchy.…
Pair annihilation of heavy stable particles that occurs in the early universe is reconsidered including the off-shell effect not properly taken into account by the conventional Boltzmann equation approach. Our new calculation of the time…
Scalar dark matter (DM), and axions in particular, have an irreducible abundance of particles produced by freeze-in due to portal interactions with the Standard Model plasma in the early Universe. In addition, vacuum misalignment and other…
Calculating the abundance of thermally produced dark matter particles has become a standard procedure, with sophisticated methods guaranteeing a precision that matches the percent-level accuracy in the observational determination of the…
Several lectures for non-experts on equilibrium and non-equilibrium kinetics in expanding universe are presented. An establishment of thermal equilibrium in the ealry universe as well as mechanisms leading to deviations from the equilibrium…
We consider the behavior of the particles at ultra relativistic energies, for both the Klein-Gordon and Dirac equations. We observe that the usual description is valid for energies such that we are outside the particle's Compton wavelength.…
The decoupling of a cold relic, during a decaying-particle-dominated cosmological evolution is analyzed, the relic density is calculated both numerically and semi-analytically and the results are compared with each other. Using plausible…
Light dark-matter ($M\leq20$ MeV) particles freeze out after neutrino decoupling. If the dark-matter particle couples to a neutrino or an electromagnetic plasma, the late time entropy production from dark-matter annihilation can change the…
Kinetic decoupling of dark matter typically happens much later than chemical freeze-out. In fact, local thermal equilibrium is an important assumption for the usual relic density calculations based on solving the Boltzmann equation (for its…