Related papers: Entropy production in the early-cosmology pionic p…
We look at the entropy production during the lepton era in the early Universe by using a model where we exclude all particles except the leptons and photons. We assume a temperature dependent viscosity as calculated recently by one of us…
(Abridged)The temperature (T) and entropy (S) fields of baryonic gas/IGM are analyzed using simulation samples by a cosmological hydro/N-body code. We show that in the nonlinear regime the dynamical similarity between the IGM and dark…
We study production and equilibration of pions and muons in relativistic electron-positron-photon plasma at a temperature $T\ll m_\mu, m_\pi $. We argue that the observation of pions and muons can be a diagnostic tool in the study of the…
It is shown that the vacuum-like energy of the Higgs potential at non-zero temperatures leads, in the course of the cosmological expansion, to a small but non-negligible rise of the entropy density in the comoving volume. This increase is…
We expose briefly the role of entropy in the early universe and in particular the importance of searching for new mechanisms of entropy production. We describe a mechanism that shows how entropy is produced during early annihilations and…
We reanalyze the conditions under which we have a primordial thermal population of axions. Compared with previous studies, we find other processes, involving gluons and quarks, that dominate at high temperatures. We conclude that if the…
We report on simulations of the formation of the first stars in the Universe, where we identify regions of hot atomic gas (fH2 < 10-6) at densities above 10-14 g/cc, heated to temperatures ranging between 3000 and 8000 K. Within this…
We study the production of entropy in the context of a nonequilibrium chiral phase transition. The dynamical symmetry breaking is modeled by a Langevin equation for the order parameter coupled to the Bjorken dynamics of a quark plasma. We…
A very simplified model of the Universe is considered in order to propose an alternative approach to the irreversible evolution of the Universe at very early times. The entropy generation at the quantum stage can be thought as a consequence…
We investigate the possible formation of a Bose-Einstein condensed phase of pions in the early Universe at nonvanishing values of lepton flavor asymmetries. A hadron resonance gas model with pion interactions, based on first-principle…
A brief review of the Hadron Gas model with reference to high energy heavy ion collisions is presented. The entropy dependence on temperature and baryonic chemical potential is numerically calculated, together with the entropy distribution…
The cosmological entropy production is studied in the (1+3+6)-dimensional space-times consisting of the outer space (the 3-dimensional expanding section) and the inner space (the 6-dimensional section). The inner space expands initially and…
It is argued that the entropy bound places an upper limit of about 1 TeV on the temperature of the last reheating era in the early Universe. Implications for inflation and non-standard paradigms for beyond the standard model of hot…
We study particle production and its density evolution and equilibration in hot dense medium. One type of hot dense medium, which we study, is hadronic gas produced at quark gluon plasma hadronization in heavy ions collisions in SPS, RHIC…
There exists the "entropy problem" of the early universe, that is, why did the universe begin with an extremely low entropy and how did it evolve into such high entropy at late times? It has been long believed that inflation cannot be the…
We estimate the entropy associated to a background of squeezed cosmic gravitons, and we argue that the process of cosmological pair production from the vacuum may explain the large amount of entropy of our present universe.
Gravitons produced from quantum vacuum fluctuations during an inflationary stage in the early Universe have zero entropy as far as they reflect the time evolution (squeezing) of a pure state, their large occupation number notwithstanding. A…
The Peccei-Quinn solution to the strong CP problem provides a motivated framework rich in cosmological consequence. Thermal axion production is unavoidable if there is a thermal bath at early times. Scattering and decay processes of bath…
Certain thermal non-equilibrium situations, outside of the astrophysical realm, suggest that entropy production extrema, instead of entropy extrema, are related to stationary states. In an effort to better understand the evolution of…
We study the entropy production of an open quantum system surrounded by a complex environment consisting of several heat baths at different temperatures. The detailed balance is elaborated in view of the distinguishable channels provided by…