Extensions of two-field mimetic gravity

TL;DR

This paper broadens the framework of two-field mimetic gravity by exploring a more general conformal limit, extending the theory's flexibility, and demonstrating its robustness in mimicking dark matter under various modifications.

Contribution

It introduces a more general conformal factor solution, extends the action with additional terms, and allows arbitrary mimetic constraints, significantly expanding the theoretical landscape of two-field mimetic gravity.

Findings

Generalized the conformal factor A, broadening mimetic constraints.

Extended the action with extra terms, linking to known theories.

Dark matter-like behavior persists under various extensions.

Abstract

Two-field mimetic gravity was recently realized by looking at the singular limit of the conformal transformation between the auxiliary metric and the physical metric with two scalar fields involved. In this paper, we reanalyze the singular conformal limit and find a more general solution for the conformal factor A, which greatly broadens the form of two-field mimetic constraint and thus extends the two-field mimetic gravity. We find the general setup still mimics the roles of dark matter at the cosmological background level. Moreover, we extend the action by introducing extra possible term for phenomenological interests. Surprisingly, some special cases are found to be equivalent to general relativity, k-essence theory and Galileon theory. Finally, we further extend the theory by allowing the expression of mimetic constraint to be arbitrary without imposed condition, and show that the dark matter-like behavior is unaffected even in this extension.