Constraints on Extra-Dimensions and Variable Constants from Cosmological Gamma-Ray Bursts

Abstract

Abstract. The observation of the time delay between the soft emission and the high-energy radiation from cosmological gamma ray bursts can be used as an important observational test of multi-dimensional physical theories. The main source of the time delay is the variation of the electromagnetic coupling, due to dimensional reduction, which induces an energy dependence of the speed of light. For photons with energies around 1 TeV, the time delay could range from a few seconds in the case of Kaluza-Klein models to a few days for models with large extra-dimensions. Based on these results we suggest that the detection of the 18-GeV photon ∼4500 s after the keV/MeV burst in GRB 940217 provides a strong evidence for the existence of extra-dimensions. The time delay of photons, if observed by the next generation of high energy detectors, like, for example, the SWIFT and GLAST satellite based detectors, or the VERITAS ground-based TeV gamma-ray instrument, could differentiate between the different models with extra-dimensions.

Photon emission from bare quark stars

“…Thus the theoretical situation with the photon bremsstrahlung from the electrosphere is still controversial and uncertain. The main problem here, which was not solved in the previous analyses [13,14,15], is an accurate accounting for the photon energy in the electron Pauli-blocking. In the present paper we address the bremsstrahlung from the electrosphere in a way similar to the Arnold-Moore-Yaffe (AMY) [16] approach to the collinear photon emission from a hot quark-gluon plasma based on the thermal field theory.…”

“…In this way they obtained the radiated energy flux from the e − e − → e − e − γ process which is much smaller than that in [13], and than the energy flux from the tunnel e + e − pair creation [4,10]. In [15] there was an initial attempt to include the effect of the mean Coulomb field of the electrosphere on the photon emission. The authors obtained a considerable enhancement of the radiation rate.…”

“…The authors obtained a considerable enhancement of the radiation rate. However, similarly to [13] the analysis [15] treats incorrectly the Pauli-blocking effect. Note also that in the analyses [14,15] the photon quasiparticle mass was neglected.…”

“…However, similarly to [13] the analysis [15] treats incorrectly the Pauli-blocking effect. Note also that in the analyses [14,15] the photon quasiparticle mass was neglected. As we will show this approximation is clearly inadequate since the finite photon mass suppresses the radiation rate strongly.…”

“…It allows to evaluate the photon emission accounting for bending of the electron trajectories in the mean Coulomb potential of the electrosphere. Contrary to very crude and qualitative methods of [13,14,15] the treatment of the Pauli-blocking effects in [16,17] has robust quantum field theoretical grounds. Of course, our approach is only valid in the regime of collinear photon emission when the dominating photon energies exceed several units of the photon quasiparticle mass.…”