Discrete and finite Genral Relativity

We develop the General Theory of Relativity in a formalism with extended causality that describes physical interaction through discrete, transversal and localized pointlike fields. The homogeneous field equations are then solved for a finite, singularity-free, point-like field that we associate to a ``classical graviton". The standard Einstein's continuous formalism is retrieved by means of an averaging process, and its continuous solutions are determined by the chosen imposed symetry. The Schwarzschild metric is obtained by the imposition of spherical symmetry on the averaged field.Comment: Modified conform the version to appear in Classical and Quantum Gravit

Electromagnetic Form Factors and the Hypercentral CQM

New results about the electromagnetic form factors of the nucleon are obtained with a semirelativistic version of the hypercentral constituent quark model (hCQM) and a relativistic current. The complex structure of the constituent quarks is taken into account implicitly by means of phenomenological constituent quark form factors. We obtain a detailed reproduction of the experimental data up to $5 GeV^2$, moreover our findings about constituent quark root mean square radii are of the same order than the recent ones obtained analyzing the proton structure functions.Comment: 11 pages, 4 figure

Is room-temperature superconductivity with phonons possible?

By recognizing the vital importance of two-hole Cooper pairs (CPs) in addition to the usual two-electron ones in a strongly-interacting many-electron system, the concept of CPs was re-examined with striking conclusions. Based on this, Bose-Einstein condensation (BEC) theory has been generalized to include not boson-boson interactions (also neglected in BCS theory) but rather boson-fermion (BF)interaction vertices reminiscent of the Frohlich electron-phonon interaction in metals. Unlike BCS theory, the GBEC model is not a mean-field theory restricted to weak-coupling as it can be diagonalized exactly. In weak coupling it reproduces the BCS condensation energy. Each kind of CP is responsible for only half the condensation energy. The GBEC theory reduces to all the old known statistical theories as special cases including the so-called "BCS-Bose crossover" picture which in turn generalizes BCS theory by not assuming that the electron chemical potential equals the Fermi energy. Indeed, a BCS condensate is precisely the weak-coupling limit of a GBE condensate with equal numbers of both types of CPs. With feasible Cooper/BCS model interelectonic interaction parameter values, and even without BF interactions, the GBEC theory yields transition temperatures [including room-temperature superconductivity (RTSC)] substantially higher than the BCS ceiling of around 45K, without relying on non-phonon dynamics involving excitons, plasmons, magnons or otherwise purely-electronic mechanisms.Comment: 14 pages, 2 figures, Mini-course delivered at "X Training Course in the Physics of Correlated-Electron Systems and High Tc Superconductors" Salerno, Italy, 3-14 October, 200

The OPERA experiment: on the way to the direct observation of νμ→ντ\nu_\mu \to \nu_\tau oscillation

OPERA (\emph{O}scillation \emph{P}roject with \emph{E}mulsion t\emph{R}acking \emph{A}pparatus) is a long-baseline neutrino experiment, designed to provide the first direct proof of $\nu_\mu \to \nu_\tau$ oscillation in the atmospheric sector using the \emph{C}ERN \emph{N}eutrinos to \emph{G}ran \emph{S}asso (CNGS) $\nu_\mu$ beam. The detector, consisting of a modular target made of lead - nuclear emulsion units complemented by electronic trackers and muon spectrometers, has been conceived to select $\rm{\nu_\tau}$ charged current interactions, among all neutrino flavour events, through the observation of the outcoming tau leptons and subsequent decays. In this paper, the detector, the event analysis chain and the preliminary results from the first OPERA physics run are reported.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

On the propagation of semiclassical Wigner functions

We establish the difference between the propagation of semiclassical Wigner functions and classical Liouville propagation. First we re-discuss the semiclassical limit for the propagator of Wigner functions, which on its own leads to their classical propagation. Then, via stationary phase evaluation of the full integral evolution equation, using the semiclassical expressions of Wigner functions, we provide the correct geometrical prescription for their semiclassical propagation. This is determined by the classical trajectories of the tips of the chords defined by the initial semiclassical Wigner function and centered on their arguments, in contrast to the Liouville propagation which is determined by the classical trajectories of the arguments themselves.Comment: 9 pages, 1 figure. To appear in J. Phys. A. This version matches the one set to print and differs from the previous one (07 Nov 2001) by the addition of two references, a few extra words of explanation and an augmented figure captio

A theory of stochastic integration for bond markets

We introduce a theory of stochastic integration with respect to a family of semimartingales depending on a continuous parameter, as a mathematical background to the theory of bond markets. We apply our results to the problem of super-replication and utility maximization from terminal wealth in a bond market. Finally, we compare our approach to those already existing in literature.Comment: Published at http://dx.doi.org/10.1214/105051605000000548 in the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org