The QCD vacuum as a disordered medium: A simplified model for the QCD Dirac operator

We model the QCD Dirac operator as a power-law random banded matrix (RBM) with the appropriate chiral symmetry. Our motivation is the form of the Dirac operator in a basis of instantonic zero modes with a corresponding gauge background of instantons. We compare the spectral correlations of this model to those of an instanton liquid model (ILM) and find agreement well beyond the Thouless energy. In the bulk of the spectrum the (dimensionless) Thouless energy of the RBM scales with the square root of system size in agreement with the ILM and chiral perturbation theory. Near the origin the scaling of the (dimensionless) Thouless energy in the RBM remains the same as in the bulk which agrees with chiral perturbation theory but not with the ILM. Finally we discuss how this RBM should be modified in order to describe the spectral correlations of the QCD Dirac operator at the finite temperature chiral restoration transition.Comment: 4 pages, 3 figure

Neutrino Masses and Mixing: Where We Stand and Where We are Going

In this talk I review our present knowledge on neutrino masses and mixing as well as the expectations from near future experiments.Comment: 19 Pages, 11 figures. Review talk given at the 10th International Conference on Supersymmetry and Unification of Fundamental Interactions, SUSY02 (June 17-23, 2002, DESY, Hamburg

Impact of two mass-scale oscillations on the analysis of atmospheric and reactor neutrino data

We study the stability of the results of 3-nu oscillation analysis of atmospheric and reactor neutrino data under departures of the one--dominant mass scale approximation. In order to do so we perform the analysis of atmospheric and reactor neutrino data in terms of three--neutrino oscillations where the effect of both mass differences is explicitly considered. We study the allowed parameter space resulting from this analysis as a function of the mass splitting hierarchy parameter alpha = Delta m^2/Delta M^2 which parametrizes the departure from the one--dominant mass scale approximation. We consider schemes with both direct and inverted mass ordering. Our results show that in the analysis of atmospheric data the derived range of the largest mass splitting, Delta M^2$, is stable while the allowed ranges of mixing angles sin^2 theta_{23} and sin^2 theta_{13} are wider than those obtained in the one--dominant mass scale approximation. Inclusion of the CHOOZ reactor data in the analysis results into the reduction of the parameter space in particular for the mixing angles. As a consequence the final allowed ranges of parameters from the combined analysis are only slightly broader than when obtained in the one--dominant mass scale approximation.Comment: Updated data, references added and typos corrected. Version to appear in Eur.Phys.J.

Status of Global Analysis of Neutrino Oscillation Data

In this talk we discuss some details of the analysis of neutrino data and our present understanding of neutrino masses and mixing. This talk is based on hep-ph/0306001, hep-ph/0306226 and hep-ph/0404085.Comment: 10 pages, LaTeX file using ws-procs9x6, 6 figures included. Talk given by MCGG at the 5th Workshop on "Neutrino Oscillations and their Origin" (NOON2004), Tokyo, Japan, February 11-15, 200