# Static Spherically Symmetric Einstein-aether models II: Integrability and the Modified Tolman-Oppenheimer-Volkoff approach

## TL;DR

This paper explores the existence of analytic solutions in Einstein-ther theory for static spherically symmetric spacetimes, analyzing the modified TOV equations and their physical implications for perfect fluid and scalar field models.

## Contribution

It provides a detailed dynamical system analysis and identifies conditions under which analytic solutions exist in Einstein-ther theory, highlighting modifications to the TOV equations.

## Key findings

- Analytic solutions exist with Laurent expansion for perfect fluids with linear EoS.
- The TOV equations are significantly modified in Einstein-ther theory.
- Equilibrium points of fluid and scalar field models are characterized and analyzed.

## Abstract

We investigate the existence of analytic solutions for the field equations in the Einstein-\ae ther theory for a static spherically symmetric spacetime and provide a detailed dynamical system analysis of the field equations. In particular, we investigate if the gravitational field equations in the Einstein-\ae ther model in the static spherically symmetric spacetime possesses the Painlev\`e property, so that an analytic explicit integration can be performed. We find that analytic solutions can be presented in terms of Laurent expansion only when the matter source consists of a perfect fluid with linear equation of state (EoS) $\mu =\mu _{0}+\left( \texttt{h} -1\right) p,~\texttt{h} >1$. In order to study the field equations we apply the Tolman-Oppenheimer-Volkoff (TOV) approach and other approaches. We find that the relativistic TOV equations are drastically modified in Einstein-\ae ther theory, and we explore the physical implications of this modification. We study perfect fluid models with a scalar field with an exponential potential. We discuss all of the equilibrium points and discuss their physical properties.