Light speed variation in a string theory model for space-time foam

• Published in: Physics letters. B Vol. 819; p. 136443
• Main Authors: Li, Chengyi, Ma, Bo-Qiang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.08.2021; Elsevier
• Subjects: Gamma-ray burst; Light speed variation; Lorentz invariance violation; Stringy space-time foam; Light speed variation; Gamma-ray burst; Stringy space-time foam; Lorentz invariance violation
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2021.136443

We revisit a supersymmetric string model for space-time foam, in which bosonic open-string states, such as photons, can possess quantum-gravity-induced velocity fluctuations in vacuum. We argue that the suggestion of light speed variation with lower bound from gamma-ray burst photon time delays can serve as a support for this string-inspired framework, through connecting the experimental finding with model predictions. We also derive the value of the effective quantum-gravity mass in this framework, and give a qualitative study on the model-dependent coefficients. Constraints from birefringent effects and/or photon decays, including the novel γ-decay constraint obtained here from the latest Tibet ASγ near-PeV photon, are also found to be consistent with predictions in such a quantum-gravity scheme. Future observation that can testify further the theory is suggested.