Nonlinear logarithmic interactions and a varying polytropic gas

Abstract

In this paper, we constructed and demonstrated possible existence of some exotic forms of non-gravitational interaction. In particular, the construction has been done assuming that dark energy in considered models is a varying polytropic fluid suggested recently by one of us. Ongoing research in both directions, i.e. dark energy and non-gravitational interaction, opens very interesting perspectives for solving the problems which are related to the accelerated expansion of the Universe. The fact that available observational data allows to parametrize the dark side of the Universe in the form of interacting dark fluids is not less surprising than the accelerated expansion itself. Therefore, the consideration of new forms of non-gravitational interactions in modern cosmology is still one of the actual topics and requires deep and systematic research. On the other hand, the BOSS experiment announcement about the Hubble value parameter at z = 2.34 allows some authors to conclude that it is going to be an evidence on the existence of non-gravitational interaction between dark energy and dark matter. Concerning this, in this paper we will demonstrate that a specific form of a varying polytropic fluid can do it without requiring any non-gravitational interaction if the Hubble parameter value will be quite less than its present value reported by other missions. Actually, this fact motivates us also to consider various new forms of non-gravitational logarithmic interactions and study their cosmological and BOSS experiment result consequences. A classification of the models in the light of actively discussed Om analysis is also presented in this work allowing also to obtain some constraints on the model parameters.