# On (in)stabilities of perturbations in mimetic models with higher derivatives

## TL;DR

This paper investigates the stability issues in mimetic gravity models with higher derivatives and proposes a solution involving direct couplings to spacetime curvature to overcome ghost and gradient instabilities.

## Contribution

It introduces a novel approach of coupling higher derivatives of the mimetic field directly to spacetime curvature to address instabilities.

## Key findings

- Direct couplings can stabilize mimetic models
- Overcoming ghost and gradient instabilities
- Potential for more viable early universe models

## Abstract

Usually when applying the mimetic model to the early universe, higher derivative terms are needed to promote the mimetic field to be dynamical. However such models suffer from the ghost and/or the gradient instabilities and simple extensions cannot cure this pathology. We point out in this paper that it is possible to overcome this difficulty by considering the direct couplings of the higher derivatives of the mimetic field to the curvature of the spacetime.