Warm anisotropic inflationary universe model

M Sharif,Rabia Saleem

doi:10.1140/epjc/s10052-014-2738-1

M Sharif, Rabia Saleem

Open Access

https://doi.org/10.1140/epjc/s10052-014-2738-1

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Abstract

This paper is devoted to study the warm inflation using vector fields in the background of locally rotationally symmetric Bianchi type I universe model. We formulate the field equations, slow-roll and perturbation parameters (scalar and tensor power spectra as well as their spectral indices) under slow-roll approximation. We evaluate all these parameters in terms of directional Hubble parameter during intermediate and logamediate inflationary regimes by taking the dissipation factor as a function of scalar field as well as a constant. In each case, we calculate the observational parameter of interest, i.e., tensor-scalar ratio in terms of inflation. The graphical behavior of these parameters shows that the anisotropic model is also compatible with WMAP7 and Planck observational data.

Highlights

The standard cosmology successfully explains the observations of cosmic microwave background (CMB) radiation, but still there are some unresolved issues
In the context of cosmology, it has become an undeniable fact through the combined efforts of type Ia supernova, the large scale structure (LSS), cosmic microwave background (CMB), and WMAP studies that the universe is undergoing a stage of accelerating expansion [1,2,3,4,5,6,7]
Golovnev et al [26] discussed the vector inflation models based on an orthogonal triplet, non-minimally coupled to gravity, which shows a similar behavior as the scalar fields in a flat universe

Summary

Introduction

[15,16,17,18]. The standard cosmology (big-bang model) successfully explains the observations of CMB radiation, but still there are some unresolved issues. Ghosts are associated with the longitudinal vector polarization present in these models, and they are found from studying the sign of eigenvalues of the kinetic matrix for the physical perturbations They introduce two main problems: firstly, they make the theories ill defined at the quantum level in the high energy regime; secondly, they create an instability already at the linearized level. In a recent paper [51], Setare and Kamali have discussed warm vector inflation in intermediate and logamediate scenarios for the FRW model and proved the physical compatibility of these results with WMAP7 data [5,47,48] through the perturbed parameters.

Basic formalism and perturbations

Intermediate inflation

Logamediate inflation

Findings

Concluding remarks