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Reassessing aspects of the photon's LQG-modified dispersion relations

Published 16 Jan 2025 in hep-th, gr-qc, and hep-ph | (2501.09370v1)

Abstract: Our present contribution sets out to investigate a scenario based on the effects of the Loop Quantum Gravity (LQG) on the electromagnetic sector of the Standard Model of Fundamental Interactions and Particle Physics (SM). Starting then from a post-Maxwellian version of Electromagnetism that includes LQG effects, we work out and discuss the influence of LQG parameters on classical quantities, such as the components of the stress-tensor. Furthermore, we inspect the propagation of electromagnetic waves and study optical properties of the QED vacuum in this scenario. Among these, we contemplate the combined effect between the LQG parameters and a homogeneous background magnetic field on the propagation of electromagnetic waves, considering in detail issues like group velocities and refractive indices of the QED vacuum. Finally, with the help of the LQG-extended photonic dispersion relations previously analyzed, we re-discuss the kinematics of the Compton effect and conclude that there emerges an interesting nonlinear profile in the wavelengths of both the incoming and the deflected photons.

Summary

  • The paper demonstrates that LQG corrections significantly alter photon dispersion relations and classical electromagnetic energy expressions.
  • It employs analytical methods to reveal deviations in light propagation and the Compton effect, simplifying traditional QED models.
  • The findings pave the way for experimental tests in high-energy astrophysics and future studies in quantum gravity and electroweak interactions.

Reassessing Aspects of the Photon's LQG-Modified Dispersion Relations

The paper "Reassessing Aspects of the Photon's LQG-Modified Dispersion Relations" by Mourão, Levy, and Helayel-Neto presents an analytical exploration of the impacts of Loop Quantum Gravity (LQG) on electromagnetic phenomena. Focusing on the photon sector, the authors thoroughly examine how the LQG-induced modifications affect dispersion relations, optical properties of the Quantum Electrodynamics (QED) vacuum, and the classical expressions of key electromagnetic quantities.

Loop Quantum Gravity, a non-perturbative and background-independent approach to quantizing gravity, posits the discrete structure of spacetime, evidently influencing the kinematics of particle interactions governed by Standard Model (SM) formalisms. In this study, the authors extend traditional electrodynamics to incorporate LQG modifications, thereby revealing alterations in light propagation and interaction manifesting at the Planck scale.

Notably, the research investigates how LQG modulations affect classical electromagnetic constructs, such as the energy-momentum tensor and radiation energy expressions. Such modifications present significant deviations from the Maxwellian model, highlighting contributions from LQG rotating angles on various components. This treatment not only enriches the electromagnetic energy density and the shear stresses but also prominently affects the photon dispersion relation.

A significant element of the study is the analysis of LQG's impact on the Compton effect, which aligns historically as a probe into quantum interactions. Differing from conventional Compton scattering, the LQG-modified scenarios introduce additional factors into the wavelength shift calculations. Despite retaining the core physics, the dispensation omits contributions from nonlinear magnetic terms, simplifying the expression yet rendering it apt for theoretical discussions and potential empirical validation.

The presented LQG-corrected formulations yield intricate yet plausible constructs for assessing new physics beyond the current observational capabilities. Although primarily theoretical, this framework enables high-energy astrophysical phenomena as prospective testbeds, offering insights into Lorentz-invariance violations, recognized as observable effects in such domains. Particularly, phenomena like Gamma-Ray Bursts and Active Galactic Nuclei show promise as cosmic laboratories for studying the hypothesized deviations.

In interpreting the broader implications, the research underscores the potential of the modified parameters for furthering investigations into dark energy phenomena and validating other LQG predictions. Furthermore, it sets the stage for future works that may seek analogous corrections to the electroweak interactions governed by the Yang-Mills theories, probing anomalous neutral gauge boson couplings via LHC experimental data.

This paper contributes meaningfully to the discourse on quantizing gravity, delineating how LQG may redefine standard notions of space-time dynamics and particle interactions. While arduous challenges remain in experimentally verifying these implications due to high precision demands and the sensitivity of instrumentation, the research explores the foundations necessary for future explorations in quantum gravity and high-energy physics.

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