# Vacuum Cherenkov radiation for nonminimal dimension-5 Lorentz violation

## TL;DR

This paper investigates vacuum Cherenkov radiation within a Lorentz-violating extension of the Standard Model, analyzing its properties and using cosmic ray data to set bounds on Lorentz violation parameters.

## Contribution

It provides a detailed analysis of vacuum Cherenkov radiation for dimension-5 Lorentz-violating operators, deriving decay rates and energy loss, and constrains Lorentz violation using astrophysical observations.

## Key findings

- Derived decay and energy radiated rates as functions of fermion momentum.
- Established bounds on Lorentz violation parameters from cosmic ray non-observation.
- Confirmed vacuum Cherenkov radiation as a physical phenomenon under Lorentz violation.

## Abstract

Vacuum Cherenkov radiation is investigated in the Lorentz-violating Standard-Model Extension for isotropic dim-5 operators $\hat{m}$ and $\hat{a}^{\mu}$ in the fermion sector. Both the kinematics and dynamics of this process are analyzed by analytical and numerical means, leading to its decay and radiated-energy rates as functions of the initial-fermion momentum. We adopt the point of view that vacuum Cherenkov radiation is actually a physical phenomenon expected to occur for a charged, massive fermion in the presence of Lorentz violation, when some additional requirements are satisfied. The absence of this effect in ultrahigh-energy cosmic rays detected on Earth allows us to infer stringent bounds on isotropic dim-5 Lorentz violation in protons, quarks, and electrons.