A substantial fraction of prompt GRB spectra have soft spectral indexes exceeding the maximum allowed by the synchrotron model αmax = −2/3. Some spectra also exhibit very sharp break at Ep, inconsistent with the smooth synchrotron spectra. These facts pose a serious problem for the “optically thin synchrotron” interpretation of the prompt emission. We review various models suggested in order to...

Acoustic communication is widespread in animals. According to the sensory drive hypothesis [Endler JA (1993) Philos Trans R Soc Lond B Biol Sci 340(1292):215-225], communication signals and perceptual systems have coevolved. A clear illustration of this is the evolution of the tetrapod middle ear, adapted to life on land. Here we report the discovery of a bone conduction-mediated stimulation of...

BeppoSAX observations of Mkn501 in April 1997 (Pian et al. 1998), have revealed an extraordinary X–ray emission from this BL Lac object, during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA and CAT Cerenkov telescopes. The 0.1–200 keV spectrum was hard, and the X–ray power output peaked at or above 100 keV, 2 or 3 orders of magnitude more than what indicated by ...

BeppoSAX observations of Mkn501 in April 1997 (Pian et al. 1998), have revealed an extraordinary X–ray emission from this BL Lac object, during a phase of high activity at TeV energies, as monitored with the Whipple, HEGRA and CAT Cerenkov telescopes. The 0.1–200 keV spectrum was hard, and the X–ray power output peaked at or above 100 keV, 2 or 3 orders of magnitude more than what indicated by ...

We study the departures from the classical synchrotron radiation due to noncommutativity of coordinates. We find that these departures are significant, but do not give tight bounds on the magnitude of the noncommutative parameter. On the other hand, these results could be used in future investigations in this direction. We also find an acausal behavior for the electromagnetic field due to the p...