Weak Magnetism in Two Neutrino Double Beta Decay

We have extended the formalism for the two-neutrino double beta decay by including the weak-magnetism term, as well as other second-forbidden corrections. The weak magnetism diminishes the calculated half-lives in $\sim 10$, independently of the nuclear structure. Numerical computations were performed within the pn-QRPA, for $^{76}Ge$, $^{82}Se$, $^{100} Mo$, $^{128}Te$ and $^{130}Te$ nuclei. No one of the second-forbidden corrections modifies significantly the spectrum shapes. The total reduction in the calculated half lives varies from 6% up to 32%, and strongly depend on the nuclear interaction in the particle-particle $S=1,T=0$ channel. We conclude that the higher order effects in the weak Hamiltonian would hardly be observed in the two-neutrino double beta experiments.Comment: 8 pages, latex, 1ps figure, to appear in Phys. Lett.

SO(4,C)-covariant Ashtekar-Barbero gravity and the Immirzi parameter

An so(4,C)-covariant hamiltonian formulation of a family of generalized Hilbert-Palatini actions depending on a parameter (the so called Immirzi parameter) is developed. It encompasses the Ashtekar-Barbero gravity which serves as a basis of quantum loop gravity. Dirac quantization of this system is constructed. Next we study dependence of the quantum system on the Immirzi parameter. The path integral quantization shows no dependence on it. A way to modify the loop approach in the accordance with the formalism developed here is briefly outlined.Comment: 14 pages, LATEX; minor changes; misprints corrected; commutator of two secondary second class constraints correcte

Operational hydro-meteorological warning and real-time flood forecasting: the Piemonte Region case study

International audienceThe development and implementation of a real-time flood forecasting system in the context of the Piemonte Region's hydro-meteorological operational alert procedure is described. The area of interest is the Upper Po River basin (north-west Italy) of approximately 37000 km2 and its river network of about 3000 km and three big lakes. FloodWatch, a GIS-based decision support system for real-time flood forecasting, has been developed and used operationally at the Piemonte Region's Room for the Situation of Natural Hazards in Torino, Italy, since January 2000. The system is linked directly to the telemetric gauges system, uses daily quantitative precipitation and temperature forecasts issued by the Regional Meteorological Service and automatically supplies operational forecasts of water-level and discharge at about 30 locations for up to 48 hours. Strengths and limits of the system and its link with operational flood alert and management are discussed. The case study presented is the October 2000 flood event, when the north-west of Italy experienced one of the largest floods on record. Results highlight how the uncertainty linked to the use of meteorological forecasts greatly influences the quality of the hydrological forecasts. The proposed alert procedure, based on coded risk levels, can help effectively in facing forecast uncertainties

Nuclear moments for the neutrinoless double beta decay II

The recently developed formalism for the evaluation of nuclear form factors in neutrinoless double beta decay is applied to $^{48}Ca$, $^{76}Ge$, $^{82}Se$, $^{100}Mo$, $^{128}Te$ and $^{130}Te$ nuclei. Explicit analytical expressions that follows from this theoretical development, in the single mode model for the decay of $^{48}Ca$, have been worked out. They are useful both for testing the full numerical calculations, and for analytically checking the consistency with other formalisms. Large configuration space calculations are compared with previous studies, where alternative formulations were used. Yet, besides using the G-matrix as residual interaction, we here use a simple $\delta$-force. Attention is paid to the connected effects of the short range nuclear correlations and the finite nucleon size. Constraints on lepton number violating terms in the weak Hamiltonian (effective neutrino Majorana mass and effective right-handed current coupling strengths) are deduced.Comment: 18 pages, latex, minor changes, to appear in Nucl. Phys.

Remarks on the Reduced Phase Space of (2+1)-Dimensional Gravity on a Torus in the Ashtekar Formulation

We examine the reduced phase space of the Barbero-Varadarajan solutions of the Ashtekar formulation of (2+1)-dimensional general relativity on a torus. We show that it is a finite-dimensional space due to existence of an infinite dimensional residual gauge invariance which reduces the infinite-dimensional space of solutions to a finite-dimensional space of gauge-inequivalent solutions. This is in agreement with general arguments which imply that the number of physical degrees of freedom for (2+1)-dimensional Ashtekar gravity on a torus is finite.Comment: 13 pages, Latex. More details have been included and the expression for the finite residual gauge transformations has been worked ou