179 research outputs found
Numerical Calculation of Hubble Hierarchy Parameters and Observational Parameters of Inflation
We present results obtained by a software we developed for computing
observational cosmological inflation parameters: the scalar spectral index
() and the tensor-to-scalar ratio () for a standard single field and
tachyon inflation, as well as for a tachyon inflation in the second
Randall-Sundrum model with an additional radion field. The calculated numerical
values of observational parameters are compared with the latest results of
observations obtained by the Planck Collaboration. The program is written in
C/C++. The \textit{GNU Scientific Library} is used for some of the numerical
computations and R language is used for data analysis and plots.Comment: 8 pages, 5 figures, based on talk presented at The 10th Jubilee
Conference of the Balkan Physical Union (BPU10), 26-30 August 2018 (Sofia,
Bulgaria
Inflationary RSII Model with a Matter in the Bulk and Exponential Potential of Tachyon Field
In this paper we study a tachyon cosmological model based on dynamics of a
3-brane in the second Randall-Sundrum (RSII) model extended to include matter
in the bulk. The presence of matter in the bulk changes warp factor which leads
to modification of inflationary dynamics. The additional brane behaves
effectively as a tachyon. We calculate numerically observation parameters of
inflation: the scalar spectral index () and the tensor-to-scalar ratio
() for the exponential potential of tachyon field.Comment: 9 pages, 1 figure, will be published in the Special Issue of Facta
Universitatis, Series: Physics, Chemistry and Technology devoted to the
SEENET-MTP Balkan Workshop BSW2018 (3-14 June 2018
Superluminal pions in a hadronic fluid
We study the propagation of pions at finite temperature and finite chemical
potential in the framework of the linear sigma model with 2 quark flavors and
colors. The velocity of massless pions in general differs from that of
light. One-loop calculations show that in the chiral symmetry broken phase
pions, under certain conditions, propagate faster than light.Comment: 8 pages, 3 figures included. Considerably revised, discussions
expanded, one figure added, typos corrected, results unchanged. To be
published in Phys. Rev.
Generalized Chaplygin Gas Model: Dark Energy - Dark Matter Unification and CMBR Constraints
The generalized Chaplygin gas (GCG) model allows for an unified description
of the recent accelerated expansion of the Universe and the evolution of energy
density perturbations. This dark energy - dark matter unification is achieved
through an exotic background fluid whose equation of state is given by , where is a positive constant and .
Stringent constraints on the model parameters can be obtained from recent WMAP
and BOOMERanG bounds on the locations of the first few peaks and troughs of the
Cosmic Microwave Background Radiation (CMBR) power spectrum as well as SNe Ia
data.Comment: 9 pages, 2 figures; essay selected for an honorable mention by the
Gravity Research Foundation, 200
INFLATIONARY RSII MODEL WITH A MATTER IN THE BULK AND EXPONENTIAL POTENTIAL OF TACHYON FIELD
In this paper, we study a tachyon cosmological model based on the dynamics of a 3-brane in the second Randall-Sundrum (RSII) model extended to include matter in the bulk. The presence of matter in the bulk changes the warp factor which leads to the modification of inflationary dynamics. The additional brane behaves effectively as a tachyon. We calculate numerically observation parameters of inflation: the scalar spectral index (ns) and the tensor-to-scalar ratio (r) for the exponential potential of the tachyon field
Ghost Condensate Busting
Applying the Thomas-Fermi approximation to renormalizable field theories, we
construct ghost condensation models that are free of the instabilities
associated with violations of the null-energy condition.Comment: 9 pages, minor corrections, a reference added, the discussion on
consistency of the Thomas-Fermi approximation expanded, to appear in JCA
Confronting particle emission scenarios with strangeness data
We show that a hadron gas model with continuous particle emission instead of
freeze out may solve some of the problems (high values of the freeze out
density and specific net charge) that one encounters in the latter case when
studying strange particle ratios such as those by WA85. This underlines the
necessity to understand better particle emission in hydrodynamics to be able to
analyze data. It also re-opens the possibility of a quark-hadron transition
occuring with phase equilibrium instead of explosively.Comment: 13 pages, 2 figures, to appear in Phys. Rev. Let
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