Cherenkov radiation as ghost instability

TL;DR

This paper reveals that Cherenkov radiation can be understood as a manifestation of ghost instabilities in modified gravity theories, linking two phenomena through their underlying causal structures.

Contribution

It establishes a novel interpretation of Cherenkov radiation as ghost instability, providing new insights into the causal structure of modified gravity theories.

Findings

Cherenkov radiation corresponds to ghost instabilities in certain theories.

Different species with distinct causal cones lead to vacuum decay.

The paper bridges Cherenkov radiation and ghost instabilities conceptually.

Abstract

We demonstrate that Cherenkov radiation can be interpreted as ghost instability of a certain type. Solutions of modified gravity theories often contain ghost instabilities. One type of such ghost instability is associated with existence of different types of species with causal cones that do not share common time, which leads to vacuum decay via creation of particles with positive and negative energies. We show that this ghost instability can be seen as Cherenkov radiation and vice versa.