Towards wormhole beyond Horndeski

Abstract

We address the issue of whether a no-go theorem for static, spherically symmetric wormholes, proven in Horndeski theories, can be circumvented by going beyond Horndeski. We show that the ghost instabilities which are at the heart of the no-go theorem, can indeed be avoided. The wormhole solutions with the latter property are, however, strongly fine tuned, and hence it is likely that they are unstable. Furthermore, it remains unclear whether these solutions have other pathologies, like gradient instabilities along angular and radial direc-

Stable wormholes in scalar-tensor theories

“…Diagonalizing the matrix c 2 r = 1 a 2 A −1 B with A and B given in (24) and (25), one can easily compute the speeds of propagation along the radial direction:…”

Bounce in general relativity and higher-order derivative operators

“…It might be also interesting to apply the EFT (24) to regulate the singularity of the BH, e.g. [46][47][48].…”

More about stable wormholes in beyond Horndeski theory

“…Such a construction has been attempted in Ref. [33] where we presented static, spherically symmetric wormhole in beyond Horndeski theory which, we argued, did not have ghost instabilities among parity even 4 There is a claim [12,13] that there exists a stable static wormhole in a dilaton-Gauss-Bonnet gravity. This solution, however, appears unstable even against spherically symmetric perturbations [14].…”