Higher dimensional Bianchi type-I string cosmological model in f(R) theory of gravity

In this paper, we have studied Bianchi type-I string cosmological model by combining Kaluza-Klein (KK) theory and $$ theory of gravity which is an extension of 5-dimensional KK string cosmological models. We have used equation of state in the form of p-string or Takabayasi string given by $$ , where ρ and λ denote the rest density of energy cloud of strings, and the tension density of the system of strings, respectively and ω is a constant. In order to get physically significant and viable solution various forms of the function $$ are assumed, in this paper we assume $$ (e.g. Astashenok et al. (2017) [1]), where α is real number. Some physical and geometrical properties of the model are also discussed.