scholarly journals Possible Effects of Non-Vanishing Particle Sizes in the Early Universe

1997 ◽  
Vol 12 (38) ◽  
pp. 2927-2931 ◽  
Author(s):  
Hidezumi Terazawa
Keyword(s):  
Early Universe ◽  
Quark Gluon Plasma ◽  
Baryon Number ◽  
Gluon Plasma ◽  
Effective Radius ◽  
Inflationary Universe ◽  
Particle Sizes ◽  
Friedmann Model ◽  
Quark Number ◽  
The Universe

Possible effects of the non-vanishing sizes of particles (atoms, nuclei, nucleons, quarks, and leptons) in the early universe (the temperature T) are discussed in an extended Friedmann model of the universe (the scale a). In particular we point out the following possibilities: (a) if rq>(2NB/π)-1/3a, most of the proposed scenarios for T>103 TeV including the inflationary universe are unrealistic, (b) rq<(2NB/π)-1/3a due to the smallness of rq(≲ 10-27 cm ), (c) rq<(2NB/π)-1/3a due to the smallness of NB in which the baryon number (or quark number) must be generated at T≲03 TeV if rq≳ 10-17 cm (where rq and NB are the effective radius of quarks and the baryon number in the universe, respectively), and (d) for T≳ 103 TeV , the universe was filled not with quark–gluon plasma but with "subquark plasma".

scholarly journals SUPERHEAVY PARTICLES IN FRIEDMANN COSMOLOGY AND THE DARK MATTER PROBLEM

2002 ◽  
Vol 11 (03) ◽  
pp. 433-436 ◽  
Author(s):  
A. A. GRIB ◽  
YU. V. PAVLOV
Keyword(s):  
Dark Matter ◽  
Gravitational Field ◽  
Early Universe ◽  
Particle Creation ◽  
Baryon Number ◽  
Matter Density ◽  
Friedmann Model ◽  
Dark Matter Density ◽  
The Universe

The model of creation of observable particles and particles of the dark matter, considered to be superheavy particles, due to particle creation by the gravitational field of the Friedmann model of the early Universe is given. Estimates on the parameters of the model leading to observable values of the baryon number of the Universe and the dark matter density are made.

scholarly journals Reactions Governing Strangeness Abundance in Primordial Universe

2020 ◽  
Author(s):  
JOHANN RAFELSKI ◽  
Cheng Tao Yang
Keyword(s):  
Early Universe ◽  
Chemical Equilibrium ◽  
Quark Gluon Plasma ◽  
Detailed Balance ◽  
Gluon Plasma ◽  
Back Reaction ◽  
Production Processes ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Hubble Time

Strangeness flavor is abundant and in chemical equilibrium in the primordial Quark-Gluon Plasma(QGP) filling the early Universe. Upon hadronization near to T=150 MeV one may think that relatively short lived massive strange hadrons decay rapidly and strangeness disappears. However, we show using detailed balance considerations for inverse decay reactions that the back reaction repopulate strangeness keeping it in chemical equilibrium at least to the time when strange antibaryons annihilate near T≃30-50 MeV. However, our present study is focused on the meson sector of the hadronic Universe. Specifically, we establish here the temperature range in which the expansion of the Universe becomes faster compared to the production processes which balance natural strangeness decay: In the temperature interval 33MeV&amp;lt;T&amp;lt;20MeV: μ±+νμ→K±, π+π→K and l−+l+→ϕ reactions in sequence become slower compared to the characteristic Hubble time.

scholarly journals QCD PHASE TRANSITION IN DGP BRANE COSMOLOGY

2012 ◽  
Vol 21 (08) ◽  
pp. 1250069 ◽  
Author(s):  
K. ATAZADEH ◽  
A. M. GHEZELBASH ◽  
H. R. SEPANGI
Keyword(s):  
Phase Transition ◽  
Energy Density ◽  
Early Universe ◽  
Effective Temperature ◽  
Quark Gluon Plasma ◽  
Friedmann Equation ◽  
Gluon Plasma ◽  
High Energy ◽  
Brane World ◽  
High Energy Density

In the standard picture of cosmology it is predicted that a phase transition, associated with chiral symmetry breaking after the electroweak transition, has occurred at approximately 10μ seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider the quark-hadron phase transition in a Dvali, Gabadadze and Porrati (DGP) brane world scenario within an effective model of QCD. We study the evolution of the physical quantities useful for the study of the early universe, namely, the energy density, temperature and the scale factor before, during and after the phase transition. Also, due to the high energy density in the early universe, we consider the quadratic energy density term that appears in the Friedmann equation. In DGP brane models such a term corresponds to the negative branch (ϵ = -1) of the Friedmann equation when the Hubble radius is much smaller than the crossover length in 4D and 5D regimes. We show that for different values of the cosmological constant on a brane, λ, phase transition occurs and results in decreasing the effective temperature of the quark-gluon plasma and of the hadronic fluid. We then consider the quark-hadron transition in the smooth crossover regime at high and low temperatures and show that such a transition occurs along with decreasing the effective temperature of the quark-gluon plasma during the process of the phase transition.

scholarly journals Inflationary universe models and clustering of quasar red shifts

1986 ◽  
Vol 119 ◽  
pp. 509-510
Author(s):  
C. Sivaram
Keyword(s):  
Cosmological Model ◽  
Early Universe ◽  
Hubble Constant ◽  
Matter Density ◽  
Inflationary Universe ◽  
Expansion Phase ◽  
Exponential Expansion ◽  
The Universe ◽  
Inflationary Models ◽  
Universe Models

Recently it has been shown that many of the puzzling features of conventional cosmological models (such as the horizon and flatness problems) could be explained by invoking inflationary models of the early universe with an exponential expansion phase at very early epochs. These models have the added advantage that they are able to make a definite prediction about the present matter density in the universe, i.e. they require that the density be exactly equal to the closure density which in turn can be easily estimated from the Hubble constant now known to within a factor of two. Now if one goes back to an earlier idea that explored the possibility of unusual clustering of quasar redshifts around z = 2 or 3, we get an example of another cosmological model with a definite prediction for the present overall matter density. This is a modified version of the Eddington-Lemaitre type of model which naturally accommodates such features as a clustering of quasars at certain epochs. From these models one can get a prediction for the present matter density which would be an involved function of the Hubble constant and the redshifts at which such clustering occurs. It can be shown that if such clustering had occurred at any z, the present matter density predicted would be substantially smaller than the corresponding closure density. The conclusion is that any clustering of quasar redshifts is incompatiable with inflationary universe models, indirectly providing observational support for these new theories.

scholarly journals Nonextensive statistical effects in the quark-gluon plasma formation at relativistic heavy-ion collisions energies

Open Physics ◽  
2012 ◽  
Vol 10 (3) ◽  
Author(s):  
Gianpiero Gervino ◽  
Andrea Lavagno ◽  
Daniele Pigato
Keyword(s):  
Quark Gluon Plasma ◽  
Mean Field ◽  
Relativistic Equation ◽  
Baryon Number ◽  
Heavy Ion ◽  
Gluon Plasma ◽  
Baryon Density ◽  
Hadronic Matter ◽  
Relativistic Heavy Ion Collisions ◽  
Relativistic Mean Field

AbstractWe investigate the relativistic equation of state of hadronic matter and quark-gluon plasma at finite temperature and baryon density in the framework of the non-extensive statistical mechanics, characterized by power-law quantum distributions. We impose the Gibbs conditions on the global conservation of baryon number, electric charge and strangeness number. For the hadronic phase, we study an extended relativistic mean-field theoretical model with the inclusion of strange particles (hyperons and mesons). For the quark sector, we employ an extended MIT-Bag model. In this context we focus on the relevance of non-extensive effects in the presence of strange matter.

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