Dark energy

Could the black hole singularity be a field singularity?

In the wake of interest to find black hole solutions with scalar hair, we investigate the effects of disformal transformations on static spherically symmetric space-times with a non-trivial scalar field. In particular, we study solutions that have a …

Exploring theories of gravity

Is general relativity the theory of gravity?

Vector disformal transformation of generalized Proca theory

Motivated by the GW170817/GRB170817A constraint on the deviation of the speed of gravitational waves from that of photons, we study disformal transformations of the metric in the context of the generalized Proca theory. The constraint restricts the …

Doppelgänger dark energy: modified gravity with non-universal couplings after GW170817

Gravitational Wave (GW) astronomy severely narrowed down the theoretical space for scalar-tensor theories. We propose a new class of attractor models {for Horndeski action} in which GWs propagate at the speed of light in the nearby universe but not …