Abstract

We investigate the possibility of inflation with models of antisymmetric tensor field having minimal and nonminimal couplings to gravity. Although the minimal model does not support inflation, the nonminimal models, through the introduction of a nonminimal coupling to gravity, can give rise to stable de-Sitter solutions with a bound on the coupling parameters. The values of field and coupling parameters are sub-planckian. Slow roll analysis is performed and slow-roll parameters are defined which can give the required number of e-folds for sufficient inflation. Stability analysis has been performed for perturbations to antisymmetric field while keeping the metric unperturbed, and it is found that only the sub-horizon modes are free of ghost instability for de-Sitter space.

Highlights

  • Inflation as a theory, has been successfull in describing the structure and evolution of our universe [1,2]

  • Many theories have considered the scalar field called “inflaton” as the source for inflation and are able to describe the cosmology of universe [4,5,6,7,8,9]

  • Most of the scalar field models having simple form of potential are ruled out as they are not compatible with the Planck’s observational data for the cosmic microwave background [3,10,11]. Another class of models considers a vector field as an alternative to the inflaton [12,13,14,15,16]. Almost all of these models suffer from instabilities like ghost instability [17] and gradient instability [18] which leads to an unstable vacuum

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Summary

Introduction

Inflation as a theory, has been successfull in describing the structure and evolution of our universe [1,2]. We study the possibility of inflation with antisymmetric tensor field by considering minimal and nonminimal models originally considered in Altschul et al [37]. [42] a similar instability analysis was done for R coupling and possibility of ghosts was found, the present analysis is different in the following ways: (1) the spacetime is isotropic and homogeneous; (2) background structure of Bμν is specified; and (3) choice of parameter space takes into account the conditions for slowrolling inflation. 2, we introduce background structures of the metric and the antisymmetric tensor, and establish the general setup of our analysis through a simple model of a massive antisymmetric tensor field minimally coupled to gravity.

Minimal model and the setup
Minimal model
The models
Stability analysis of the de-Sitter background
Slow roll parameters
Stability of perturbations to Bμν
Conclusion
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