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# Addendum: Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified-Maxwell theory

• ##### M. Risse
Physical review D: Particles and fields 07/2008; DOI: 10.1103/PHYSREVD.77.117901
Source: arXiv

ABSTRACT Nonbirefringent modified-Maxwell theory, coupled to standard Dirac particles, involves nine dimensionless parameters, which can be bounded by the inferred absence of vacuum Cherenkov radiation for ultrahigh-energy cosmic rays (UHECRs). With selected UHECR events, two-sided bounds on the eight nonisotropic parameters are obtained at the 10^{-18} level, together with an improved one-sided bound on the single isotropic parameter at the 10^{-19} level.

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