Subir Sarkar

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The recent confirmation that at least some gamma-ray bursters (GRBs) are indeed at cosmological distances [1, 2, 3, 4] raises the possibility that observations of these could provide interesting constraints on the fundamental laws of physics. Here we demonstrate that the fine-scale time structure and hard spectra of GRB emissions are very sensitive to the(More)
Received (received date) Revised (revised date) A satisfactory theory of quantum gravity will very likely require modification of our classical perception of space-time, perhaps by giving it a 'foamy' structure at scales of order the Planck length. This is expected to modify the propagation of photons and other relativistic particles such as neutrinos, such(More)
The temperature uctuations in the cosmic microwave background observed by COBE provide strong support for an innationary phase in the early universe, below the GUT scale. We argue that a singlet eld in a hidden sector of an eeective supergravity theory yields the required innationary potential without ne tuning. Reheating occurs to a temperature low enough(More)
We discuss possible signatures of quantum gravity for the propagation of light, including an energy-dependent velocity (refractive index), dispersion in velocity at a given energy, and birefringence. We also compare the sensitivities of different astrophysical observations, including BATSE data on GRB 920229, BeppoSAX data on GRB 980425, the possible HEGRA(More)
We derive constraints on the relic abundance of a generic particle of mass ∼ 1 − 10 14 TeV which decays into neutrinos at cosmological epochs, using data from the Fréjus and IMB nucleon decay detectors and the Fly's Eye air shower array. The lifetime of such unstable particles which may constitute the dark matter today is bounded to be greater than ∼ 10 14(More)
We study the impact of the assumed velocity distribution of galactic dark matter particles on the interpretation of results from nuclear recoil detectors. By converting experimental data to variables that make the astrophysical unknowns explicit, different experiments can be compared without implicit assumptions concerning the dark matter halo. We extend(More)