Quantum Gravity Phenomenology Induced in the Propagation of UHECR, a Kinematical Solution in Finsler and Generalized Finsler Spacetime

• Published in: Galaxies 2021-12, Vol.9 (4), p.103
• Main Author: Torri, Marco Danilo Claudio
• Format: Article
• Language: English
• Subjects: astroparticle physics; Attenuation; Context; Cosmic microwave background; Cosmic ray showers; Cosmic rays; Covariance; doubly special relativity; Energy; Energy dissipation; Fermions; finsler geometry; Gravity; Horizon; Hypotheses; Investigations; Kinematics; lorentz invariance violation; Magnetic fields; Opacity; Particle physics; Perturbation; Phenomenology; Propagation; Quantum field theory; Quantum gravity; Quantum phenomena; Radiation; Relativity; Spacetime; Theory of relativity; Universe
• ISSN: 2075-4434; 2075-4434
• DOI: 10.3390/galaxies9040103

It is well-known that the universe is opaque to the propagation of Ultra-High-Energy Cosmic Rays (UHECRs) since these particles dissipate energy during their propagation interacting with the background fields present in the universe, mainly with the Cosmic Microwave Background (CMB) in the so-called GZK cut-off phenomenon. Some experimental evidence seems to hint at the possibility of a dilation of the GZK predicted opacity sphere. It is well-known that kinematical perturbations caused by supposed quantum gravity (QG) effects can modify the foreseen GZK opacity horizon. The introduction of Lorentz Invariance Violation can indeed reduce, and in some cases making negligible, the CMB-UHECRs interaction probability. In this work, we explore the effects induced by modified kinematics in the UHECR lightest component phenomenology from the QG perspective. We explore the possibility of a geometrical description of the massive fermions interaction with the supposed quantum structure of spacetime in order to introduce a Lorentz covariance modification. The kinematics are amended, modifying the dispersion relations of free particles in the context of a covariance-preserving framework. This spacetime description requires a more general geometry than the usual Riemannian one, indicating, for instance, the Finsler construction and the related generalized Finsler spacetime as ideal candidates. Finally we investigate the correlation between the magnitude of Lorentz covariance modification and the attenuation length of the photopion production process related to the GZK cut-off, demonstrating that the predicted opacity horizon can be dilated even in the context of a theory that does not require any privileged reference frame.