Constraints on birefringence-free photon theory within standard-model extension

TL;DR

The paper tests birefringence-free LV operators in the photon sector of the SME using 14 GeV GRB photons and a theory-agnostic Bayesian framework to constrain isotropic coefficients $c_{(I)00}^{(d)}$ for $d=6,8,10$. By modeling observed delays as a sum of intrinsic delays and LV-induced dispersion, and focusing on the isotropic monopole term, the authors obtain tight 95% bounds: $|c_{(I)00}^{(6)}|\\le 7.75 imes 10^{-20}$ GeV$^{-2}$, $|c_{(I)00}^{(8)}|\\\\le 4.92 imes 10^{-24}$ GeV$^{-4}$, and $|c_{(I)00}^{(10)}|\\\\le 3.46 imes 10^{-28}$ GeV$^{-6}$. The analysis indicates a preference for subluminal LV, consistent with stability considerations for high-energy photons, and represents improvements of several orders of magnitude over previous bounds. The work highlights the potential of high-energy GRB photons to probe nonrenormalizable LV operators in EFT frameworks and sets the stage for tighter future constraints with more data.

Abstract

Constraints on the birefringence-free subset of Lorentz-violating (LV) operators are derived using 14 GRB photons in the GeV-band. These constraints target the isotropic $c_{(I)00}^{(d)}$ coefficients for dimensions $d=6,8,10$ within the framework of the Standard-Model Extension (SME). Employing theory-agnostic Bayesian parameter estimation methods, our analysis indicates a preference for subluminal LV effects. Focusing on this case, we further refine the parameter constraints, yielding results that are mutually consistent. Within the 95\% posterior credible interval, our constraints yield the bounds, $|c_{(I)00}^{(6)}|\le7.75 \times 10^{-20} ~ {\rm GeV}^{-2}$, $|c_{(I)00}^{(8)}|\le4.92 \times 10^{-24} ~ {\rm GeV}^{-4}$, and $|c_{(I)00}^{(10)}|\le3.46 \times 10^{-28} ~ {\rm GeV}^{-6}$, which improve upon the most stringent credible-interval bounds reported in the literature by at least five orders of magnitude.

Figures (2)

• Figure 1: The results for constraining $d=6$, $d=8$, $d=10$ operators with agnosticism prior are shown in the left, middle, and right panel. The 2D contours represent with different credible levels, denoting the 1$\sigma$, 2$\sigma$, and 3$\sigma$ regions, while the vertical lines indicate the 95% region for the 1D marginalized posterior distribution.
• Figure 2: Same as Fig. \ref{['agnosticism_prior_intrinsic_params']} but for subluminal prior.