Approaches to photon absorption in a Lorentz invariance violation scenario

TL;DR

This paper refines the calculation of gamma-ray absorption in the universe under Lorentz Invariance Violation, providing new expressions and approximations that improve constraints on LIV effects at ultra-high energies.

Contribution

It introduces a new cross section expression and an approximation method for photon absorption in LIV scenarios, surpassing previous models.

Findings

New cross section expression for photon absorption in LIV.

Refined constraints on LIV scale from gamma-ray observations.

Enhanced modeling for future ultra-high energy gamma-ray data.

Abstract

Very high-energy astrophysical gamma rays suffer a suppression of their flux along their propagation due to their interaction, through the $\gamma\gamma\to e^+e^-$ pair-production process, with the soft photon backgrounds present in the Universe. We examine the Universe's transparency to gamma rays within a Lorentz Invariance Violation (LIV) framework, focusing on photon subluminal quadratic corrections driven by a high-energy scale. Based on an explicit calculation, we provide a new expression for the cross section that overcomes the limitations of previous approaches and refines existing constraints for the LIV scale, while we introduce a new approximation that may be useful in LIV scenarios beyond effective field theory. These improvements appear essential for setting constraints on LIV effects with future observations at ultra-high energies, where previous approximations may fall short.