Qualitative analysis of Einstein-aether models with perfect fluid and scalar fields

TL;DR

This paper performs a qualitative analysis of Einstein-aether models coupled with perfect fluids and scalar fields, exploring their solution space using dynamical systems techniques and numerical verification.

Contribution

It introduces a method to analyze Einstein-aether models with matter fields using homothetic symmetry and qualitative dynamical systems analysis.

Findings

Solutions exhibit behaviors similar to homogeneous models.

Numerical verification supports analytical results.

The approach simplifies complex PDEs to ODEs for qualitative study.

Abstract

The space of the solutions of the differential equations resulting from considering matter fluids of scalar field type or perfect fluid in Einstein-aether theory is analyzed. The Einstein-aether theory of gravity consists of General Relativity coupled to a vector field of unit time type, called the aether. In this effective theory, Lorentz invariance is violated, but locality and covariance are preserved in the presence of the vector field. For the mathematical formulation of the models, the 1 + 3 formalism is used that allows writing field equations for spherically symmetric inhomogeneous metrics as a system of partial differential equations in two variables. Using the homothetic diagonal formulation, the Partial differential equations can be written as ordinary differential equations plus algebraic constraints, using the fact that the metric adapts to homothetic symmetry. The resulting equations are very similar to those of the models with homogeneous hypersurfaces. This allows the qualitative study of the solutions using techniques of local theory of dynamic systems. Analytical results are verified numerically.