Opening Pandora's box: Kundt solutions to Conformal Killing Gravity

TL;DR

This paper explores Kundt solutions within Conformal Killing Gravity, revealing numerous solutions in various dimensions and highlighting the need for criteria to select physically relevant ones for explaining cosmic acceleration.

Contribution

It provides a comprehensive analysis of Kundt solutions in CKG, demonstrating the theory's rich solution space and implications for cosmological modeling.

Findings

Numerous Kundt solutions found in 4D and higher dimensions.

Cosmological constant emerges as an integration constant in CKG.

A large solution space necessitates criteria for physical relevance.

Abstract

We consider Kundt solutions to vacuum Conformal Killing Gravity (CKG) proposed by Harada and find numerous solutions in four dimensions and in higher dimensions. In CKG theory the cosmological constant appears as an integration constant, and hence, is naturally embedded in the theory. However, by considering Kundt solutions to CKG we seemingly open Pandora's box: We find so many solutions so a selection criterium is needed in CKG to explain the current accelerated expansion of the universe.