Individual GRB sensitivity of a cubic-kilometer deep-sea neutrino telescope KM3NeT

Gamma-ray bursts (GRB) are powerful and highly variable sources of gamma rays that indicate the existence of cosmic particle accelerators. Under the assumption of hadronic acceleration in the jet, the expected neutrino energy spectrum is derived according to the intrinsic fireball model parameters and to the observed electromagnetic data of GRBs measured with ground-based and satellite observations. Using the performance characteristics of a cubic-kilometre scale neutrino detector placed in the Mediterranean Sea, the number of events is calculated individually for all the GRBs having a known redshift below the horizon of this detector. The good angular resolution of this detector and the narrow time windows around the GRB detection time allow suppression of almost all the atmospheric neutrino background. From the SWIFT GRB catalogue, we have derived the mean characteristics of a burst in order to be detected as an individual point source by a cubic-kilometre detector.Comment: 4 pages proceeding for the Very Large Volume Neutrino Telescopes VLVNT 0

Mapping Self-Organized Criticality onto Criticality

We present a general conceptual framework for self-organized criticality (SOC), based on the recognition that it is nothing but the expression, ''unfolded'' in a suitable parameter space, of an underlying {\em unstable} dynamical critical point. More precisely, SOC is shown to result from the tuning of the {\em order parameter} to a vanishingly small, but {\em positive} value, thus ensuring that the corresponding control parameter lies exactly at its critical value for the underlying transition. This clarifies the role and nature of the {\em very slow driving rate} common to all systems exhibiting SOC. This mechanism is shown to apply to models of sandpiles, earthquakes, depinning, fractal growth and forest-fires, which have been proposed as examples of SOC.Comment: 17 pages tota

Five-dimensional Superfield Supergravity

We present a projective superspace formulation for matter-coupled simple supergravity in five dimensions. Our starting point is the superspace realization for the minimal supergravity multiplet proposed by Howe in 1981. We introduce various off-shell supermultiplets (i.e. hypermultiplets, tensor and vector multiplets) that describe matter fields coupled to supergravity. A projective-invariant action principle is given, and specific dynamical systems are constructed including supersymmetric nonlinear sigma-models. We believe that this approach can be extended to other supergravity theories with eight supercharges in $D\leq 6$ space-time dimensions, including the important case of 4D N=2 supergravity.Comment: 18 pages, LaTeX; v2: comments added; v3: minor changes, references added; v4: comments, reference added, version to appear in PL