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S Liberati

Publications and source records attributed to S Liberati.

4 recordsLinked to original sources
PubMed2004

New limits on Planck scale Lorentz violation in QED.

Constraints on possible Lorentz symmetry violation (LV) of order E/M(Planck) for electrons and photons in the framework of effective field theory (EFT) are discussed. Using (i) the report of polarized MeV emission from GRB021206 and (ii) the absence of vacuum Cerenkov radiation from synchrotron electrons in the Crab Nebula, we improve previous bounds by 10(-10) and 10(-2), respectively. We also show that the LV parameters for positrons and electrons are different, discuss electron helicity decay, and investigate how prior constraints are modified by the relations between LV parameters implied by EFT.

Journal Article↗
PubMed2003

A strong astrophysical constraint on the violation of special relativity by quantum gravity.

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 discreteness or non-commutivity of space-time, or through the action of extra dimensions. 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.

Journal Article↗