Screening anisotropy via energy-momentum squared gravity: ACDM model with hidden anisotropy


Akarsu Ö. , Barrow J. D. , Uzun N. M.

PHYSICAL REVIEW D, cilt.102, sa.12, 2020 (SCI İndekslerine Giren Dergi) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 102 Konu: 12
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1103/physrevd.102.124059
  • Dergi Adı: PHYSICAL REVIEW D

Özet

We construct a generalization of the standard ACDM model, wherein we simultaneously replace the spatially flat Robertson-Walker metric with its simplest anisotropic generalization (LRS Bianchi I metric), and couple the cold dark matter to the gravity in accordance with the energy-momentum squared gravity (EMSG) of the form f (T mu vT mu v) proportional to T mu vT mu v. These two modifications-namely, two new stiff fluid-like terms of different nature-can mutually cancel out, i.e., the shear scalar can be screened completely, and reproduce mathematically exactly the same Friedmann equation of the standard ACDM model. This evades the BBN limits on the anisotropy, and thereby provides an opportunity to manipulate the cosmic microwave background quadrupole temperature fluctuation at the desired amount. We further discuss the consequences of the model on the very early times and far future of the Universe. This study presents also an example of that the EMSG of the form f (T mu vT mu v) proportional to T mu vT mu v, as well as similar type other constructions, is not necessarily relevant only to very early Universe but may even be considered in the context of a major problem of the current cosmology related to the present-day Universe, the so-called H-0 problem.