Phase transitions in perturbed stiff-fluid Friedmann-Robertson-Walker cosmological models

1988 ◽  
Vol 309 (4) ◽  
pp. 239-242
Author(s):  
R. J. Gleiser ◽  
M. C. Diaz ◽  
R. D. Grosso
Keyword(s):  
Phase Transitions ◽  
Cosmological Models ◽  
Stiff Fluid ◽  
Friedmann Robertson Walker

scholarly journals ENERGY–MOMENTUM IN VISCOUS KASNER-TYPE UNIVERSE IN BERGMANN–THOMSON FORMULATIONS

2005 ◽  
Vol 20 (10) ◽  
pp. 2169-2177 ◽  
Author(s):  
MUSTAFA SALTI ◽  
ALI HAVARE
Keyword(s):  
Total Energy ◽  
Space Time ◽  
Cosmological Models ◽  
Energy And Momentum ◽  
Momentum Complex ◽  
The Universe ◽  
Friedmann Robertson Walker

Using the Bergmann–Thomson energy–momentum complex and its tele-parallel gravity version, we obtain the energy and momentum of the universe in viscous Kasner-type cosmological models. The energy and momentum components (due to matter plus field) are found to be zero and this agree with a previous work of Rosen and Johri et al. who investigated the problem of the energy in Friedmann–Robertson–Walker universe. The result that the total energy and momentum components of the universe in these models is zero supports the viewpoint of Tryon. Rosen found that the energy of the Friedmann–Robertson–Walker space–time is zero, which agrees with the studies of Tryon.

scholarly journals Kinematic equivalence between models driven by DBI field with constant γ and exotic holographic quintessence cosmological models

2017 ◽  
Vol 32 (26) ◽  
pp. 1750140 ◽  
Author(s):  
Mónica Forte
Keyword(s):  
Dark Energy ◽  
Cosmological Models ◽  
Exponential Potential ◽  
Kinematic Equivalence ◽  
Friedmann Robertson Walker

We show the kinematic equivalence between cosmological models driven by Dirac–Born–Infeld (DBI) fields [Formula: see text] with constant proper velocity of the brane and exponential potential [Formula: see text], and interactive cosmological systems with modified holographic Ricci type fluids as dark energy (DE) in flat Friedmann–Robertson–Walker (FRW) cosmologies.

SOLUTIONS OF COSMOLOGICAL MODELS WITH VARYING SPEED OF LIGHT

2007 ◽  
Vol 16 (02n03) ◽  
pp. 433-437 ◽  
Author(s):  
C. S. CÂMARA ◽  
R. B. NASCIMENTO ◽  
J. C. CARVALHO ◽  
M. R. DE GARCIA MAIA
Keyword(s):  
Structure Constant ◽  
Cosmological Models ◽  
Fine Structure Constant ◽  
Speed Of Light ◽  
Frw Universe ◽  
Cosmological Time ◽  
Standard Cosmological Model ◽  
Factor C ◽  
Friedmann Robertson Walker ◽  
Constants Of Nature

In recent years, there has been some renewed interest in cosmological models in which the constants of nature vary with time. In one of these, one supposes a dependence on the redshift of the fine structure constant as suggested by some astronomical observations of quasars. This has led, among others, to the proposal that the speed of light varies with the cosmological time. A Varying Speed of Light (VSL) would be able to solve some long standing problems of the standard cosmological model, without the need for inflation. In this work we study two models in which (1) c varies according to a power law of the scale factor c(t) ∝ a-r and (2) c is proportional to the Hubble parameter c(t) ∝ Hu. We present solutions for these two types of VSL cosmologies. We find that for a flat (k = 0) Friedmann–Robertson–Walker (FRW) universe, the variation of c is coupled to a cosmological Λ-term and both singular and non-singular solutions are possible.

Tilted congruences with stiff fluid cosmological models

2019 ◽  
Vol 94 (11) ◽  
pp. 1861-1867 ◽  
Author(s):  
V. J. Dagwal ◽  
D. D. Pawar
Keyword(s):  
Cosmological Models ◽  
Stiff Fluid
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