Aether Unleashed

TL;DR

This paper explores a broad class of vector-tensor theories extending aether models, analyzing their cosmological, Newtonian, and stability properties, revealing potential links to dark matter and modifications of gravity.

Contribution

It introduces a generalized vector-tensor framework with a focus on quantum stability and cosmological viability, expanding the theoretical landscape of modified gravity models.

Findings

Quantum stability favors non-Maxwellian kinetic terms.

Gravitational constant becomes scale-dependent in the Newtonian limit.

Theories exhibit rich phenomenology with potential cosmological implications.

Abstract

We follow a low-energy effective theory approach to identify the general class of theories that describes a vector field (of unconstrained norm) coupled to gravity. The resulting set may be regarded as a generalization of the conventional vector-tensor theories, and as a high-momentum completion of aether models. We study the conditions that a viable cosmology, Newtonian limit and absence of classical and quantum instabilities impose on the parameters of our class of models, and compare these constraints with those derived in previously studied and related cases. The most stringent conditions arise from the quantum stability of the theory, which allows dynamical cosmological solutions only for a non-Maxwellian kinetic term. The gravitational constant in the Newtonian limit turns to be scale dependent, suggesting connections to dark matter and degravitation. This class of theories has a very rich gravitational phenomenology, and offers an ample but simple testing ground to study modifications of gravity and their cosmological implications.