k-Essence, superluminal propagation, causality and emergent geometry

TL;DR

This paper demonstrates that k-essence theories, despite allowing superluminal perturbation propagation, do not lead to causal paradoxes, maintaining their consistency with fundamental causality principles.

Contribution

It shows that superluminal propagation in k-essence does not cause causal paradoxes, challenging previous assumptions about superluminal theories.

Findings

Superluminal propagation occurs in k-essence theories.

Causal paradoxes are avoided despite superluminal signals.

k-essence remains consistent with causality principles.

Abstract

The k-essence theories admit in general the superluminal propagation of the perturbations on classical backgrounds. We show that in spite of the superluminal propagation the causal paradoxes do not arise in these theories and in this respect they are not less safe than General Relativity.