Palatini kinetic scalar-tensor theory: analytical and numerical solutions

TL;DR

This paper explores static spherically symmetric solutions in Palatini kinetically coupled scalar-tensor gravity, revealing wormholes, naked singularities, and non-black hole solutions, with strong null energy condition violations.

Contribution

It provides the first analytical and numerical solutions in Palatini kinetic scalar-tensor theory, including a general solution in the Jordan frame and insights into its solution space.

Findings

No black hole solutions found.

Existence of wormhole and naked singularity branches.

Presence of a non-singular asymptotically flat solution.

Abstract

We investigate static spherically symmetric solutions in the Palatini kinetically coupled scalar-tensor theory, which reduces to gravity minimally coupled to a scalar field in Einstein frame. Using the fact that the Jordan and Einstein frame are related by a reversible disformal transformation, which can be solved in closed form, we derive the general solution in the Jordan frame and show that it does not contain black holes. There is a wormhole branch and a naked singularity branch between which lies a non-singular asymptotically flat solution with kernel $M_{1,1}\times S^2$. This theory strongly violates the null energy condition.