Probing a possible vacuum refractive index with gamma-ray telescopes

TY - JOUR

T1 - Probing a possible vacuum refractive index with gamma-ray telescopes

AU - Ellis, John

AU - Mavromatos, N. E.

AU - Nanopoulos, D. V.

PY - 2009/4/13

Y1 - 2009/4/13

N2 - We have used a stringy model of quantum space-time foam to Suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on gamma-ray energy: eta - 1 similar to E-gamma/M-QG1, where M-QG is some mass scale typical of quantum gravity that may be similar to 10(18) GeV: see [J. Ellis, N.E. Mavromatos, D.V. Nanopolous, Phys. Lett. B 665 (2008) 412] and references therein. The MAGIC, HESS and Fermi gamma-ray telescopes have recently probed the possible existence of such an energy-dependent vacuum refractive index. All rind indications of time-lags for higher-energy photons, but cannot exclude the possibility that they are due to intrinsic delays at the sources. However, the MAGIC and HESS observations of time-lags in emissions from AGNs Mkn 501 and PKS 2155-304 are compatible with each other and a refractive index depending linearly on the gamma-ray energy, with M-QG1 similar to 10(18) GeV. We combine their results to estimate the time-lag Delta t to be expected for the highest-energy photon from GRB 080916c measured by the Fermi telescope, which has ail energy similar to 13.2 GeV, assuming the redshift z = 4.35 +/- 0.15 measured by GROND. In the case of a refractive index depending linearly on the gamma-ray energy we predict Delta t = 26 +/- 11 s. This is compatible with the time-lag Delta t

AB - We have used a stringy model of quantum space-time foam to Suggest that the vacuum may exhibit a non-trivial refractive index depending linearly on gamma-ray energy: eta - 1 similar to E-gamma/M-QG1, where M-QG is some mass scale typical of quantum gravity that may be similar to 10(18) GeV: see [J. Ellis, N.E. Mavromatos, D.V. Nanopolous, Phys. Lett. B 665 (2008) 412] and references therein. The MAGIC, HESS and Fermi gamma-ray telescopes have recently probed the possible existence of such an energy-dependent vacuum refractive index. All rind indications of time-lags for higher-energy photons, but cannot exclude the possibility that they are due to intrinsic delays at the sources. However, the MAGIC and HESS observations of time-lags in emissions from AGNs Mkn 501 and PKS 2155-304 are compatible with each other and a refractive index depending linearly on the gamma-ray energy, with M-QG1 similar to 10(18) GeV. We combine their results to estimate the time-lag Delta t to be expected for the highest-energy photon from GRB 080916c measured by the Fermi telescope, which has ail energy similar to 13.2 GeV, assuming the redshift z = 4.35 +/- 0.15 measured by GROND. In the case of a refractive index depending linearly on the gamma-ray energy we predict Delta t = 26 +/- 11 s. This is compatible with the time-lag Delta t

U2 - 10.1016/j.physletb.2009.02.030

DO - 10.1016/j.physletb.2009.02.030

M3 - Article

SN - 1873-2445

VL - 674

SP - 83

EP - 86

JO - Physics Letters B

JF - Physics Letters B

IS - 2

ER -