Strict Limit on CPT Violation from Polarization of Gamma-Ray Bursts

TL;DR

This study uses gamma-ray polarization measurements from distant gamma-ray bursts to set the most stringent observational limits on CPT violation in the photon sector, implying quantum gravity likely respects CPT invariance.

Contribution

It provides the tightest observational constraint on CPT violation using gamma-ray polarization data from GRBs, significantly improving previous limits.

Findings

Constrained CPT-violating parameter |\xi|<O(10^{-15})

Detected gamma-ray polarization in three GRBs with high significance

Supports the hypothesis that quantum gravity respects CPT invariance

Abstract

We report the strictest observational verification of CPT invariance in the photon sector, as a result of gamma-ray polarization measurement of distant gamma-ray bursts (GRBs), which are brightest stellar-size explosions in the universe. We detected the gamma-ray polarization of three GRBs with high significance, and the source distances may be constrained by a well-known luminosity indicator for GRBs. For the Lorentz- and CPT-violating dispersion relation E_{\pm}^2=p^2 \pm 2\xi p^3/M_{Pl}, where \pm denotes different circular polarization states of the photon, the parameter \xi is constrained as |\xi|<O(10^{-15}). Barring precise cancellation between quantum gravity effects and dark energy effects, the stringent limit on the CPT-violating effect leads to the expectation that quantum gravity presumably respects the CPT invariance.