String cosmology from fractional action with solitonic NS–NS matter and possibility of an accelerated expanding universe without dark energy

Abstract

In this study, we discuss string cosmology with solitonic NS–NS matter, which arises when dilaton coupled p-brane gas dominates the universe and is subject to a fractional action motivated from viscosity dissipative effects occurring in the universe. Exact solutions are found from the stationary conditions of the fractional action. It was observed that the universe is non-singular, undergoing accelerated expansion in time and may not be dominated by dark energy because it is strongly affected by dissipations through the fractional parameter α. The numerical ranges of α were obtained using H(z) at the 1σ level for two independent cases: a vacuum energy dominated energy and a non-dominant vacuum energy universe. Our results are in agreement with astronomical observational limits and support both string cosmology and the fractional action cosmology.