Boundary Terms and Junction Conditions for Generalized Scalar-Tensor Theories

TL;DR

This paper derives boundary terms and junction conditions for Horndeski's scalar-tensor theories, enabling analysis of vacuum tunnelling and braneworld dynamics across various spacetime dimensions.

Contribution

It provides explicit second-order equations of motion and boundary conditions for Horndeski's theories and subclasses, facilitating new studies in cosmology and high-energy physics.

Findings

Derived boundary terms for Horndeski theories

Formulated junction conditions for various subclasses

Enabled analysis of tunnelling and braneworld scenarios

Abstract

We compute the boundary terms and junction conditions for Horndeski's panoptic class of scalar-tensor theories, and write the bulk and boundary equations of motion in explicitly second order form. We consider a number of special subclasses, including galileon theories, and present the corresponding formulae. Our analysis opens up of the possibility of studying tunnelling between vacua in generalized scalar-tensor theories, and braneworld dynamics. The latter follows because our results are independent of spacetime dimension.