1. Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA

Correspondence to: T. Jacobson Correspondence and requests for materials should be addressed to T.J. (Email: jacobson@physics.umd.edu).

Abstract

Special relativity asserts that physical phenomena appear the same to all unaccelerated observers. This is called Lorentz symmetry and relates long wavelengths to short ones: if the symmetry is exact it implies that space-time must look the same at all length scales. Several approaches to quantum gravity, however, suggest that there may be a microscopic structure of space-time that leads to a violation of Lorentz symmetry. This might arise because of the discreteness¹ or non-commutivity² of space-time, or through the action of extra dimensions³. Here we determine a very strong constraint on a type of Lorentz violation that produces a maximum electron speed less than the speed of light. We use the observation of 100-MeV synchrotron radiation from the Crab nebula to improve the previous limit by a factor of 40 million, ruling out this type of Lorentz violation, and thereby providing an important constraint on theories of quantum gravity.

1. Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA

Correspondence to: T. Jacobson Correspondence and requests for materials should be addressed to T.J. (Email: jacobson@physics.umd.edu).