Hall 123

The inflationary universe in F(R) gravity with antisymmetric tensor fields and their suppression during the universe evolution

Tanmoy Paul

IACS, Kolkata

The intriguing question, why the present scale of the universe is free from
any perceptible footprints of rank-2 antisymmetric tensor fields (generally
known as Kalb-Ramond fields) is addressed. A quite natural explanation of
this issue is given from the angle of higher-curvature gravity, both in
four- and in five-dimensional spacetime. The results here obtained reveal
that the amplitude of the Kalb-Ramond field may be actually large and play
a significant role during the early universe, while the presence of
higher-order gravity suppresses this field during the cosmological
evolution, so that it eventually becomes negligible in the current
universe. Besides the suppression of the Kalb-Ramond field, the extra
degree of freedom in F(R) gravity, usually known as scalaron, also turns
out to be responsible for inflation. Such F(R) gravity with Kalb-Ramond
fields may govern the early universe to undergo an inflationary stage at
early times (with the subsequent graceful exit) for wider range of F(R)
gravity than without antisymmetric fields. Furthermore, the models—in four
and five dimensional spacetimes are linked to observational constraints,
with the conclusion that the corresponding values of the spectral index and
tensor-to-scalar ratio closely match the values provided by the Planck
survey 2018 data.