INFLATIONARY UNIVERSE WITH TACHYON FIELD

2005 ◽  
Vol 14 (10) ◽  
pp. 1831-1836 ◽  
Author(s):  
B. C. PAUL ◽  
D. PAUL
Keyword(s):  
Scalar Field ◽  
Early Universe ◽  
Field Potential ◽  
Cosmological Models ◽  
Inflationary Universe ◽  
Tachyon Field

We present an inflationary solution of the early universe considering tachyon field. The technique of Zhuravlev and Chervon to obtain inflationary cosmological models without restrictions on a scalar field potential is employed here. We note that like the scalar field, the inflationary solution obtained here with tachyon field does not depend on the potential. However, unlike the scalar field, inflation with the tachyon field is obtained for restricted values of the field to begin with. We present the potential for which one gets inflation. Unlike the scalar field potential, the tachyonic potential is not regular at all values of the field. The solution obtained here with tachyon field is new.

scholarly journals A Riccati equation based approach to isotropic scalar field cosmologies

2014 ◽  
Vol 23 (07) ◽  
pp. 1450063 ◽  
Author(s):  
Tiberiu Harko ◽  
Francisco S. N. Lobo ◽  
M. K. Mak
Keyword(s):  
Scalar Field ◽  
Evolution Equation ◽  
Interaction Potential ◽  
Arbitrary Function ◽  
Field Potential ◽  
Type Equation ◽  
Scalar Fields ◽  
Cosmological Models ◽  
Late Time ◽  
Field Equations

Gravitationally coupled scalar fields ϕ, distinguished by the choice of an effective self-interaction potential V(ϕ), simulating a temporarily nonvanishing cosmological term, can generate both inflation and late time acceleration. In scalar field cosmological models the evolution of the Hubble function is determined, in terms of the interaction potential, by a Riccati type equation. In the present work, we investigate scalar field cosmological models that can be obtained as solutions of the Riccati evolution equation for the Hubble function. Four exact integrability cases of the field equations are presented, representing classes of general solutions of the Riccati evolution equation. The solutions correspond to cosmological models in which the Hubble function is proportional to the scalar field potential plus a linearly decreasing function of time, models with the time variation of the scalar field potential proportional to the potential minus its square, models in which the potential is the sum of an arbitrary function and the square of the function integral, and models in which the potential is the sum of an arbitrary function and the derivative of its square root, respectively. The cosmological properties of all models are investigated in detail, and it is shown that they can describe the inflationary or the late accelerating phase in the evolution of the universe.

scholarly journals Singularities in Inflationary Cosmological Models

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 491
Author(s):  
Leonardo Fernández-Jambrina
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Fractional Power ◽  
Scalar Fields ◽  
Big Bang ◽  
Cosmological Models ◽  
Accelerated Expansion ◽  
Type Iv ◽  
Big Crunch ◽  
Expansion Of The Universe

Due to the accelerated expansion of the universe, the possibilities for the formation of singularities has changed from the classical Big Bang and Big Crunch singularities to include a number of new scenarios. In recent papers it has been shown that such singularities may appear in inflationary cosmological models with a fractional power scalar field potential. In this paper we enlarge the analysis of singularities in scalar field cosmological models by the use of generalised power expansions of their Hubble scalars and their scalar fields in order to describe all possible models leading to a singularity, finding other possible cases. Unless a negative scalar field potential is considered, all singularities are weak and of type IV.

scholarly journals CHAOS IN CLOSED ISOTROPIC COSMOLOGICAL MODELS WITH STEEP SCALAR FIELD POTENTIAL

1999 ◽  
Vol 08 (06) ◽  
pp. 739-750 ◽  
Author(s):  
A. V. TOPORENSKY
Keyword(s):  
Scalar Field ◽  
Chaotic Dynamics ◽  
Chaotic Behavior ◽  
Field Potential ◽  
Equation Of Motion ◽  
Cosmological Models ◽  
Field Potentials ◽  
Numerical Investigations ◽  
Analytical Studies

The dynamics of closed scalar field FRW cosmological models is studied for several types of exponentially and more than exponentially steep potentials. The parameters of scalar field potentials which allow a chaotic behavior are found from numerical investigations. It is argued that analytical studies of equation of motion at the Euclidean boundary can provide an important information about the properties of chaotic dynamics. Several types of transition from chaotic to regular dynamics are described.

scholarly journals FLUCTUATION SPECTRUM FROM A SCALAR-TENSOR BIMETRIC GRAVITY THEORY

2003 ◽  
Vol 12 (04) ◽  
pp. 697-712 ◽  
Author(s):  
M. A. CLAYTON ◽  
J. W. MOFFAT
Keyword(s):  
Scalar Field ◽  
Gravitational Waves ◽  
Early Universe ◽  
Initial Period ◽  
Field Potential ◽  
Gravity Theory ◽  
Fluctuation Spectrum ◽  
Quadratic Potential ◽  
Initial Values ◽  
Bimetric Gravity

Predictions of the CMB spectrum from a bimetric gravity theory (BGT)1 are presented. The initial inflationary period in BGT is driven by a vanishingly small speed of gravitational waves vg in the very early universe. This initial inflationary period is insensitive to the choice of scalar field potential and initial values of the scalar field. After this initial period of inflation, vg will increase rapidly and the effects of a potential will become important. We show that a quadratic potential introduced into BGT yields an approximately flat spectrum with inflation parameters: ns=0.98, nt=-0.027, αs=-3.2×10-4 and αt=-5.0×10-4, with r ≥ 0.014.

LOGAMEDIATE INFLATION ON THE BRANE

2012 ◽  
Vol 27 (18) ◽  
pp. 1250101 ◽  
Author(s):  
RAMÓN HERRERA ◽  
MARCO OLIVARES
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Observational Data ◽  
High Energy ◽  
Inflationary Universe ◽  
Universe Model ◽  
Tachyon Field ◽  
Energy Limit ◽  
High Energy Limit

Brane inflationary universe model in the context of logamediate inflation is studied. As the energy density we consider two different fields, first a standard scalar field, and then a tachyon field. In the high-energy limit we describes the conditions for theses models. The parameters of our models are constrained from the observational data.

scholarly journals CHAOTIC INFLATION ON THE RANDALL–SUNDRUM TWO-BRANE MODEL

2010 ◽  
Vol 25 (31) ◽  
pp. 2697-2713
Author(s):  
KOUROSH NOZARI ◽  
SIAMAK AKHSHABI
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Friedmann Equation ◽  
Warp Factor ◽  
Model Parameters ◽  
Stabilization Mechanism ◽  
Brane Model ◽  
Inflation Model ◽  
Bulk Scalar Field ◽  
Chaotic Inflation

We construct an inflation model on the Randall–Sundrum I (RSI) brane where a bulk scalar field stabilizes the inter-brane separation. We study impact of the bulk scalar field on the inflationary dynamics on the brane. We proceed in two different approaches: in the first approach, the stabilizing field potential is directly appeared in the Friedmann equation and the resulting scenario is effectively a two-field inflation. In the second approach, the stabilization mechanism is considered in the context of a warp factor so that there is just one field present that plays the roles of both inflaton and stabilizer. We study constraints imposed on the model parameters from recent observations.

scholarly journals RECONSTRUCTING A STRING-INSPIRED NONMINIMALLY COUPLED QUINTOM MODEL

2009 ◽  
Vol 18 (08) ◽  
pp. 1291-1301 ◽  
Author(s):  
M. R. SETARE ◽  
J. SADEGHI ◽  
A. R. AMANI
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
String Theory ◽  
Scalar Curvature ◽  
Recent Work ◽  
Nonminimal Coupling ◽  
Tachyon Field ◽  
Dynamical Dark Energy

Motivated by the recent work of Zhang and Chen,1we generalize their work to the nonminimally coupled case. We consider a quintom model of dark energy with a single scalar field T given by a Lagrangian inspired by a tachyonic Lagrangian in string theory. We consider nonminimal coupling of the tachyon field to the scalar curvature, and then we reconstruct this model in the light of three forms of parametrization for dynamical dark energy.

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