Anisotropic power-law inflation for the Dirac-Born-Infeld theory

Abstract

We find a new set of the Bianchi type I power-law expanding solutions in a string-motivated Dirac-Born-Infeld theory. Stability analysis shows that these power-law inflationary solutions remain stable with or without the contribution of the Dirac-Born-Infeld effect. We also find a new set of Bianchi type I expanding power-law solutions in a two scalar Dirac-Born-Infeld model with an additional phantom field. It is shown that the inclusion of the phantom field turns the Bianchi type I power-law solutions unstable during the inflationary phase.

Anisotropic power-law inflation for a conformal-violating Maxwell model

“…In particular, we would like to obtain a new set of power-law analytic solutions with the form [43,44,[47][48][49][50][51][52]:…”

“…In order to understand the stability of the set of power-law solutions, we will consider the power-law perturbation of the field equations with δα = A α t m , δσ = A σ t m , and δφ = A φ t m [47][48][49][50][51][52]. Perturbing Eqs.…”

“…More interestingly, non-canonical extensions of the KSW model, in which a scalar field takes non-canonical form such as Dirac-Born-Infeld (DBI), supersymmetric Dirac-BornInfeld (SDBI), and covariant Galileon forms, have also been shown to admit stable and attractive Bianchi type I inflationary solutions [49][50][51][52]. This indicates that the cosmic no-hair conjecture does not hold for the extended KSW models due to the presence of the coupling term f 2 (φ)F μν F μν .…”

Statistical anisotropy from anisotropic inflation

“…Actually, a more wide range of anisotropic inflationary models are discussed in [50]. We can extend the standard kinetic term to the Born-Infeld type [51,52,53]. In this direction, we may find a stringy realization of anisotropic inflation.…”

MHz gravitational waves from short-term anisotropic inflation

“…It should be stressed that anisotropic inflation can be naturally realized in the context of supergravity. After the discovery of anisotropic inflation, many cosmological predictions [18][19][20][21][22][23][24][25][26][27][28][29][30][31] and further extension to various models [32][33][34][35][36][37][38][39][40][41][42][43][44][45] have been discussed. Importantly, anisotropic inflation can be tested with observations [46][47][48][49][50][51][52][53].…”