# K-essence and kinetic gravity braiding models in two-field measure theory

## TL;DR

This paper explores two-field measure theory models, showing k-essence can unify dark matter and dark energy, while kinetic gravity braiding exhibits diverse behaviors including phantom energy and stiff matter.

## Contribution

It demonstrates how two-field measure theory can produce unified dark sector models and characterizes the varied cosmological behaviors of kinetic gravity braiding.

## Key findings

- K-essence models imply a fluid unifying dark matter and dark energy.
- Kinetic gravity braiding models can produce phantom energy, stiff matter, or a cosmological constant.
- In some cases, the scalar field has no effect on cosmic dynamics.

## Abstract

We show that, in the context of the two-field measure theory, any k-essence model leads to the existence of a fluid made of non-relativistic matter and cosmological constant that would explain the dark matter and dark energy problem at the same time. On the other hand, kinetic gravity braiding models can lead to different behaviors, such as phantom dark energy, stiff matter, and a cosmological constant. For stiff matter, there even exists the case where the scalar field does not have any effect in the dynamics of the Universe.