The solution of the cosmological constant problem from the inhomogeneous equation of state - a hint from modified gravity?

TL;DR

This paper explores a two-component cosmological model with an inhomogeneous equation of state, proposing a mechanism where the universe's expansion relaxes a large cosmological constant to a small effective value, potentially solving the cosmological constant problem.

Contribution

It introduces a model with an inhomogeneous equation of state that allows the universe to relax a large cosmological constant to a small effective one, linking it to modified gravity theories.

Findings

The universe's expansion can asymptotically approach de Sitter space despite a large initial cosmological constant.

A mechanism for the relaxation of the cosmological constant is proposed within the model.

A connection to f(R) modified gravity is established, illustrating a possible realization of the relaxation process.

Abstract

The cosmological constant problem is studied in a two component cosmological model. The universe contains a cosmological constant of an arbitrary size and sign and an additional component with an inhomogeneous equation of state. It is shown that, in a proper parameter regime, the expansion of the universe with a large absolute value of the cosmological constant may asymptotically tend to de Sitter space corresponding to a small effective positive cosmological constant. It is argued that such a behavior can be regarded as a solution of the cosmological constant problem in this model. The mechanism behind the relaxation of the cosmological constant is discussed. A connection with modified gravity theories is discussed and an example of a possible realization of the cosmological constant relaxation in f(R) modified gravity is described.