2025/02/12 by Do, Tuan Q., Dong, Phung V., Nguyen, Duy H. +1 · 2 citations
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2502.10462
In this paper, we would like to examine whether the Sáez-Ballester theory admits stable and attractive Bianchi type I inflationary solutions in the presence of a non-minimal coupling between scalar and vector fields such as f2(ϕ)FμνFμν. As a result, such a solution will be shown to exist within this theory for a suitable setup of fields. Interestingly, the considered Sáez-Ballester theory can be shown to be equivalent to the standard scalar-vector theory via a suitable field redefinition. This means that the obtained solution can be reduced to that derived in an original anisotropic inflation model proposed by Kanno, Soda, and Watanabe. Consequently, the corresponding tensor-to-scalar ratio of this solution turns out to be higher than the latest observational value of the Planck satellite (Planck 2018) due to the fact that cs, the corresponding speed of sound of scalar perturbations of the Sáez-Ballester theory, turns out to be one. This result indicates an important hint that the speed of sound, cs, could play an important role in making the corresponding non-canonical anisotropic inflation cosmologically viable in the light of the Planck 2018 data. To be more specific, we will point out that any modifications of the Sáez-Ballester theory having cs ∼ 0.1 will have a great potential to be highly consistent with the Planck 2018 data. For heuristic reasons, a simple modified version of the Sáez-Ballester theory will be proposed as a specific demonstration. As a result, we will show that this modified model admits an anisotropic power-law inflationary solution as expected.