High-Energy gamma-ray Astronomy and String Theory

Abstract

There have been observations, first from the MAGIC Telescope (July 2005) and quite recently (September 2008) from the FERMI Satellite Telescope, on non-simultaneous arrival of high-energy photons from distant celestial sources. In each case, the highest energy photons were delayed, as compared to their lower-energy counterparts. Although the astrophysics at the source of these energetic photons is still not understood, and such non simultaneous arrival might be due to non simultaneous emission as a result of conventional physics effects, nevertheless, rather surprisingly, the observed time delays can also fit excellently some scenarios in quantum gravity, predicting Lorentz violating space-time "foam" backgrounds with a non-trivial subluminal vacuum refractive index suppressed linearly by a quantum gravity scale of the order of the reduced Planck mass. In this pedagogical talk, I discuss the MAGIC and FERMI findings in this context and I argue on a theoretical model of space-time foam in string/brane theory that can accommodate the findings of those experiments in agreement with all other stringent tests of Lorentz invariance. However, I stress the current ambiguities/uncertainties on the source mechanisms, which need to be resolved first before definite conclusions are reached regarding quantum gravity foam scenarios.

34 pages latex, 12 eps figures incorporated, uses special macros. Based on invited plenary talk at DICE 2008 Conference (Castiglioncello, Italy), September 22-26 2008

References in corpus (18)

• An Exceptional VHE Gamma-Ray Flare of PKS 2155-304
• Variable VHE gamma-ray emission from Markarian 501
• Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope
• Lorentz-violation-induced arrival delays of cosmological particles
• Derivation of a Vacuum Refractive Index in a Stringy Space-Time Foam Model
• Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays
• Limits on an Energy Dependence of the Speed of Light from a Flare of the Active Galaxy PKS 2155-304
• Superluminality and UV Completion
• The Refractive Index of Curved Spacetime: the Fate of Causality in QED
• Lorentz Violation and Ultrahigh-Energy Photons
• Probes of Lorentz Violation in Neutrino Propagation
• Causality and Micro-Causality in Curved Spacetime
• New constraints on Planck-scale Lorentz Violation in QED from the Crab Nebula
• Gamma-ray polarization constraints on Planck scale violations of special relativity
• Relativistic Modified Newtonian Dynamics from String Theory?
• A model for delayed emission in a very-high energy gamma-ray flare in Markarian 501
• Bulk photons in Asymmetrically Warped Space-times and Non-trivial Vacuum Refractive Index
• GLAST and Lorentz violation

Cited by in corpus (9)

• Analysis of the consistency of parity-odd nonbirefringent modified Maxwell theory
• Implications of a Stochastic Microscopic Finsler Cosmology
• Stringy Space-Time Foam, Finsler-like Metrics and Dark Matter Relics
• White Paper and Roadmap for Quantum Gravity Phenomenology in the Multi-Messenger Era
• Physical Properties of Brane-World Black Hole Solutions via a Confining Potential
• Light Speed Variation with Brane/String-Inspired Space-Time Foam
• Lorentz violation effects in asymmetric two brane models: a nonperturbative analysis
• Stringy Space-Time Foam and High-Energy Cosmic Photons
• Constraining super-critical string/brane cosmologies with astrophysical data