相关论文: Viscosity in a Lepton-Photon Universe
In this paper we discuss some consequences of cosmological models in which the primordial cosmic matter is described by a relativistic imperfect fluid. The latter takes into account the dissipative effects (bulk viscosity) arising from…
A large lepton number asymmetry of $\mathcal{O}(0.1-1)$ at present universe might not only be allowed but also necessary for consistency among cosmological data. We show that, if a sizeable lepton number asymmetry were produced before the…
From a hydrodynamicist's point of view the inclusion of viscosity concepts in the macroscopic theory of the cosmic fluid would appear most natural, as an ideal fluid is after all an abstraction (excluding special cases such as…
The abundance of light nuclei and hyperons, that are produced in stellar environments such as supernova or binary mergers, is calculated within a relativistic mean-field model with density dependent couplings in low-density matter. Five…
We calculate the three bulk viscosity coefficients as arising from the collisions among phonons in superfluid neutron stars. We use effective field theory techniques to extract the allowed phonon collisional processes, written as a function…
Bulk viscosity may serve to damp sound waves in a system of neutrinos coupled to very light scalar particles, in the era after normal neutrino decoupling but before recombination. We calculate the bulk viscosity parameter in a minimal…
We study particle creation in the presence of bulk viscosity of cosmic fluid in the early universe within the framework of open thermodynamical systems. Since the first-order theory of non-equilibrium thermodynamics is non-causal and…
We investigate the leptogenesis via decays of heavy Majorana neutrinos which are produced non-thermally in inflaton decays. We make a comprehensive study on the leptogenesis assuming various supersymmetric (SUSY) models for hybrid, new and…
We report a calculation of the shear viscosity in a relativistic multicomponent meson gas as a function of temperature and chemical potentials. We approximately solve the Uehling-Uhlenbeck transport equation of kinetic theory, appropriate…
Based on hot big bang theory, the cosmological matter is conjectured to undergo QCD phase transition(s) to hadrons, when the universe was about $1-10 \mu$s old. In the present work, we study the quark-hadron phase transition, by taking into…
We investigate the strange particle composition of the early Universe in the hadron epoch $T_h\approx 150\ge T\ge 10$\,MeV. We study strangeness yield in thermal and chemical equilibrium constrained by prescribed entropy per baryon in a…
The shear ($\eta$) and bulk ($\zeta$) viscosities are calculated in a quasiparticle relaxation time approximation. The hadron phase is described within the relativistic mean field based model with scaled hadron masses and couplings. The…
We compute the bulk viscosity of a gas of pions at temperatures below the QCD crossover temperature, for the physical value of pion mass, to lowest order in chiral perturbation theory. Bulk viscosity is controlled by number-changing…
For temperatures $T$ ranging from a few MeV up to TeV and energy density $\rho$ up to $10^{16}~$GeV/fm$^3$, the bulk viscosity $\zeta$ is calculated in non-perturbation (up, down, strange, charm, and bottom) and perturbation theories with…
Neutrino physics in the early Universe is key to our understanding of later cosmological stages, such as primordial nucleosynthesis (BBN) or the formation of large-scale structures. The coming decade promises new experimental results to…
An improved version of the well-known Peebles-Vilenkin model unifying early inflationary era to current cosmic acceleration, is introduced in order to match with the theoretical values of the spectral quantities provided by it with the…
In this chapter, I describe bulk viscosity as a general concept, and then focus on bulk viscosity in the dense matter present in compact objects. While this review is focused on bulk viscosity in the conditions present in neutron star…
The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak…
Recent studies invoke a unified description of different neutron star observables using metamodels, which parametrize the Equation of State (EoS) of neutron star matter close to nuclear saturation density in terms of few nuclear parameters.…
We investigate the effect of $K^-$ condensed matter on bulk viscosity and r-mode instability in neutron stars. The bulk viscosity coefficient due to the non-leptonic process $n \rightleftharpoons p + K^-$ is studied here. In this…