Constraints on Einstein-aether theory after GW170817

TL;DR

This paper analyzes observational and theoretical constraints on Einstein-aether theory's parameters, especially after GW170817, narrowing down the allowed deviations in graviton speed and parameter space.

Contribution

It provides updated bounds on Einstein-aether theory parameters considering recent gravitational wave observations, highlighting the impact of GW170817 on the theory's viability.

Findings

Graviton speed deviation constrained to within 10^{-15} by GW170817.

Parameter space on (c_1, c_{14}) and (c_2, c_{14}) planes is restricted.

Strong-field neutron star sensitivities remain uncertain in new parameter ranges.

Abstract

In this paper, we carry out a systematic analysis of the theoretical and observational constraints on the dimensionless coupling constants $c_i$ ($i=1,2,3,4$) of the Einstein-aether theory, taking into account the events GW170817 and GRB 170817A. The combination of these events restricts the deviation of the speed $c_T$ of the spin-2 graviton to the range, $- 3\times 10^{-15} < c_T -1 < 7\times 10^{-16}$, which for the Einstein-aether theory implies $\left|c_{13}\right| \le 10^{-15}$ with $c_{ij} \equiv c_{i} + c_{j}$. The rest of the constraints are divided into two groups: those on the ($c_1, c_{14}$)-plane and those on the ($c_2, c_{14}$)-plane, except the strong-field constraints. The latter depend on the sensitivities $\sigma_{\ae}$ of neutron stars, which are not known at present in the new ranges of the parameters found in this paper.