Topology and Dark Energy: Testing Gravity in Voids

TL;DR

This paper explores how modifications to gravity, especially in cosmic voids, can affect dark energy's properties, potentially observable through gravitational slip and topological defects, offering new tests for gravity theories.

Contribution

It introduces a model where a massive graviton with a Galileon scalar field alters dark energy behavior and predicts observable effects in cosmic voids.

Findings

Scalar field significantly changes dark energy's equation of state in voids

Predicts a gravitational slip between metric potentials in voids

Develops a topological defect (domain wall) due to vacuum structure

Abstract

Modified gravity has garnered interest as a backstop against dark matter and dark energy (DE). As one possible modification, the graviton can become massive, which introduces a new scalar field - here with a Galileon-type symmetry. The field can lead to a nontrivial equation of state (EOS) of DE which is density-and-scale-dependent. Tension between Type Ia supernovae and Planck could be reduced. In voids the scalar field dramatically alters the EOS of DE, induces a soon-observable gravitational slip between the two metric potentials, and develops a topological defect (domain wall) due to a nontrivial vacuum structure for the field.