TY - JOUR

T1 - An anisotropic bouncing universe in non-local gravity

AU - Kumar, K. Sravan

AU - Maheshwari, Shubham

AU - Mazumdar, Anupam

AU - Peng, Jun

N1 - Publisher Copyright:
© 2021 IOP Publishing Ltd and Sissa Medialab.

PY - 2021/7

Y1 - 2021/7

N2 - We show that it is possible to realize a cosmological bouncing solution in an anisotropic but homogeneous Bianchi-I background in a class of non-local, infinite derivative theories of gravity. We show that the anisotropic shear grows slower than in general relativity during the contraction phase, peaks to a finite value at the bounce point, and then decreases as the universe asymptotes towards isotropy and homogeneity, and ultimately to de Sitter. Along with a cosmological constant, the matter sector required to drive such a bounce is found to consist of three components - radiation, stiff matter and k-matter (whose energy density decays like the inverse square of the average scale factor). Generically, k-matter exerts anisotropic pressures. We will test the bouncing solution in local and non-local gravity and show that in the latter case it is possible to simultaneously satisfy positivity of energy density and, at least in the late time de Sitter phase, avoid the introduction of propagating ghost/tachyonic modes.

AB - We show that it is possible to realize a cosmological bouncing solution in an anisotropic but homogeneous Bianchi-I background in a class of non-local, infinite derivative theories of gravity. We show that the anisotropic shear grows slower than in general relativity during the contraction phase, peaks to a finite value at the bounce point, and then decreases as the universe asymptotes towards isotropy and homogeneity, and ultimately to de Sitter. Along with a cosmological constant, the matter sector required to drive such a bounce is found to consist of three components - radiation, stiff matter and k-matter (whose energy density decays like the inverse square of the average scale factor). Generically, k-matter exerts anisotropic pressures. We will test the bouncing solution in local and non-local gravity and show that in the latter case it is possible to simultaneously satisfy positivity of energy density and, at least in the late time de Sitter phase, avoid the introduction of propagating ghost/tachyonic modes.

KW - gravity

KW - modified gravity

UR - http://www.scopus.com/inward/record.url?scp=85111483285&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2021/07/025

DO - 10.1088/1475-7516/2021/07/025

M3 - Article

AN - SCOPUS:85111483285

VL - 2021

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 7

M1 - 025

ER -