Gravitational Lenses in Generalized Einstein-Aether theory: the Bullet Cluster

TL;DR

This paper explores how Generalized Einstein-Aether theory can explain weak lensing effects in the Bullet Cluster through vector field concentrations, offering an alternative to dark matter.

Contribution

It demonstrates that GEA theory's vector field concentrations can produce lensing effects consistent with observations, providing a MOND-inspired alternative to dark matter.

Findings

Vector field concentrations cause metric deviations affecting weak lensing.

Numerical calculations show consistency with Bullet Cluster observations.

Lensing deviations can be explained without dark matter, using GEA theory.

Abstract

We study the lensing properties of an asymmetric mass distribution and vector field in Generalized Einstein-Aether (GEA) theory. As vector field fluctuations are responsible in GEA for seeding baryonic structure formation, vector field concentrations can exist independently of baryonic matter. Such concentrations would not be expected to be tied to baryonic matter except gravitationally, and so, like dark matter halos, would become separated from baryonic matter in interacting systems such as the Bullet Cluster. These vector field concentrations cause metric deviations that affect weak lensing. Therefore, the distribution of weak lensing deviates from that which would be inferred from the luminous mass distribution, in a way that numerical calculations demonstrate can be consistent with observations. This suggests that MOND-inspired theories can reproduce weak lensing observations, but makes clear the price: the existence of a coherent large-scale fluctuation of a field(s) weakly tied to the baryonic matter, not completely dissimilar to a dark matter halo.