scholarly journals Kaluza-Klein FRW cosmological models in Lyra manifold

2009 ◽  
Vol 36 (2) ◽  
pp. 157-166 ◽  
Author(s):  
G. Mohanty ◽  
G.C. Samanta ◽  
K.L. Mahanta
Keyword(s):  
Perfect Fluid ◽  
Displacement Field ◽  
Arbitrary Constant ◽  
Matter Field ◽  
Cosmological Models ◽  
Time Dependent ◽  
Infinite Time ◽  
Lyra Manifold ◽  
Kaluza Klein

We have constructed five dimensional FRW cosmological models for k=-1,1,0 in Lyra manifold with time dependent displacement field. The matter field is considered in the form of a perfect fluid with isotropic matter pressure. It is found that the model for k=-1 is inflationary. For k=1, the model is inflationary for set of values of arbitrary constant n and decelerates in the standard way for another set of values of n. Moreover the concept of Lyra manifold does not exist at infinite time.

String inspired cosmological models through Lagrangian invariance

2020 ◽  
Vol 17 (06) ◽  
pp. 2050085
Author(s):  
José Antonio Belinchón ◽  
Danae Polychroni
Keyword(s):  
Perfect Fluid ◽  
Power Law ◽  
Matter Field ◽  
Scale Factor ◽  
Cosmological Models ◽  
De Sitter ◽  
Text Field ◽  
Duality Property ◽  
Constant Potential ◽  
Variable Potential

We study a string inspired cosmological with variable potential through the Lagrangian invariance method in order to determine the form of the potential. We have studied four cases by combining the different fields, that is, the dilaton [Formula: see text] the potential [Formula: see text] the [Formula: see text]-field and the matter field (a perfect fluid). In all the studied cases, we found that the potential can only take two possible forms: [Formula: see text] and [Formula: see text] where [Formula: see text] and [Formula: see text] are numerical constants. We conclude that when we take into account the Kalb–Ramond field, i.e. the [Formula: see text]-field, then it is only possible to get a constant potential, [Formula: see text] Nevertheless, if this field is not considered, then we get two possible solutions for the potential: [Formula: see text] and [Formula: see text] In all the cases, if the potential is constant, [Formula: see text] then we get a de Sitter like solution for the scale factor of the metric, [Formula: see text], which verifies the [Formula: see text]-duality property, while if the potential varies, then we get a power-law solution for the scale factor, [Formula: see text] [Formula: see text]

Cosmological Models in Lyra Geometry with Linearly Varying Deceleration Parameter

2018 ◽  
Author(s):  
Kalyani Desikan
Keyword(s):  
Exact Solutions ◽  
Displacement Field ◽  
Deceleration Parameter ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Time Dependent ◽  
Linearly Varying Deceleration Parameter ◽  
Frw Model ◽  
Time Periods ◽  
The Universe

Cosmological models with linearly varying deceleration parameter in the cosmological theory based on Lyra’s geometry have been discussed. Exact solutions have been obtained for a spatially flat FRW model by considering a time dependent displacement field. We have also obtained the time periods during which the universe undergoes decelerated and accelerated expansions for a matter-dominated universe.

scholarly journals Five dimensional cosmological models in Lyra geometry with time dependent displacement field

2008 ◽  
Vol 317 (3-4) ◽  
pp. 283-283 ◽  
Author(s):  
G. Mohanty ◽  
K. L. Mahanta ◽  
B. K. Bishi
Keyword(s):  
Displacement Field ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Time Dependent

scholarly journals Five-Dimensional Space-Times with a Variable Gravitational and Cosmological Constant

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Sanjay Oli
Keyword(s):  
Cosmological Constant ◽  
Perfect Fluid ◽  
Gravitational Constant ◽  
Dimensional Space ◽  
Space Time ◽  
Time Dependent ◽  
Field Equations ◽  
Current Observation ◽  
Kinematical Parameters ◽  
Kaluza Klein

We have presented cosmological models in five-dimensional Kaluza-Klein space-time with a variable gravitational constant (G) and cosmological constant (Λ). We have investigated Einstein’s field equations for five-dimensional Kaluza-Klein space-time in the presence of perfect fluid with time dependent G and Λ. A variety of solutions have been found in which G increases and Λ decreases with time t, which matches with current observation. The properties of fluid and kinematical parameters have been discussed in detail.

Five dimensional cosmological models in Lyra geometry with time dependent displacement field

2007 ◽  
Vol 310 (3-4) ◽  
pp. 273-276 ◽  
Author(s):  
G. Mohanty ◽  
K. L. Mahanta ◽  
B. K. Bishi
Keyword(s):  
Displacement Field ◽  
Lyra Geometry ◽  
Cosmological Models ◽  
Time Dependent

scholarly journals COASTING COSMOLOGIES WITH TIME DEPENDENT COSMOLOGICAL CONSTANT

1999 ◽  
Vol 14 (10) ◽  
pp. 1523-1529 ◽  
Author(s):  
LUIS O. PIMENTEL ◽  
LUZ M. DIAZ-RIVERA
Keyword(s):  
Cosmological Constant ◽  
Perfect Fluid ◽  
Gravitational Constant ◽  
Linear Expansion ◽  
Cosmological Models ◽  
Time Dependent ◽  
Expansion Factor ◽  
Fluid Matter ◽  
Friedmann Robertson Walker

The effect of a time dependent cosmological constant is considered in a family of scalar-tensor theories. Friedmann–Robertson–Walker cosmological models for vacuum and perfect fluid matter are found. They have a linear expansion factor, the so-called coasting cosmology, the gravitational "constant" decreases inversely with time; that is these models satisfy the Dirac Hypotheses. The cosmological "constant" decreases inversely with the square of time, therefore we can have a very small value for it at present time.

scholarly journals FLRW Cosmological Models in Lyra's Manifold with Time Dependent Displacement Field

1988 ◽  
Vol 41 (6) ◽  
pp. 833 ◽  
Author(s):  
A Beesham
Keyword(s):  
Asymptotic Behaviour ◽  
Displacement Field ◽  
Riemannian Geometry ◽  
Cosmological Models ◽  
Time Dependent ◽  
Lyra’S Manifold ◽  
Standard Models ◽  
Horizon Problems

Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological models are derived in Lyra's manifold assuming a time dependent displacement field. The models obtained solve the singularity, entropy and horizon problems which exist in the standard models of cosmology based on Riemannian geometry. The asymptotic behaviour of the models is also examined.

Perfect fluid Bianchi type-I cosmological models with time-dependent cosmological term Λ

2018 ◽  
Vol 15 (08) ◽  
pp. 1850132
Author(s):  
J. P. Singh ◽  
Prashant S. Baghel ◽  
Abhay Singh
Keyword(s):  
Perfect Fluid ◽  
Bianchi Type ◽  
Cosmological Term ◽  
Cosmological Models ◽  
Time Dependent ◽  
Late Time ◽  
Type I ◽  
Field Equations ◽  
Vacuum Decay ◽  
Bianchi Type I

We present perfect fluid Bianchi type-I cosmological models with time-dependent cosmological term [Formula: see text]. Exact solutions of the Einstein’s field equations are presented via a suitable functional form for Hubble parameter [Formula: see text], which yields a model of the universe that represents initially decelerating and late-time accelerating expansion. We discuss, in the context of some vacuum decay laws, cosmological implications of the corresponding solutions. The physical and geometrical features of the models are also discussed.

scholarly journals Geometries with mismatched branes

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Andreas Karch ◽  
Lisa Randall
Keyword(s):  
Boundary Conditions ◽  
Effective Action ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter ◽  
Stabilization Mechanism ◽  
New Class ◽  
Vacuum Solutions ◽  
Single Coordinate

Abstract We study Randall-Sundrum two brane setups with mismatched brane tensions. For the vacuum solutions, boundary conditions demand that the induced metric on each of the branes is either de Sitter, Anti-de Sitter, or Minkowski. For incompatible boundary conditions, the bulk metric is necessarily time-dependent. This introduces a new class of time-dependent solutions with the potential to address cosmological issues and provide alternatives to conventional inflationary (or contracting) scenarios. We take a first step in this paper toward such solutions. One important finding is that the resulting solutions can be very succinctly described in terms of an effective action involving only the induced metric on either one of the branes and the radion field. But the full geometry cannot necessarily be simply described with a single coordinate patch. We concentrate here on the time- dependent solutions but argue that supplemented with a brane stabilization mechanism one can potentially construct interesting cosmological models this way. This is true both with and without a brane stabilization mechanism.

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