Measurement of the Atmospheric Muon Neutrinos with the MACRO Detector

The flux of muons induced by atmospheric neutrinos has been measured with the MACRO detector. Different event topologies have been detected, due to neutrino interactions in the apparatus and in the rock below it. The upward-throughgoing muon sample is the larger one and is generated by neutrinos with a peak energy of ~100 GeV. The observed upward-throughgoing muons are 26 % fewer than expected and the zenith angle distribution does not fit with the expected one. Assuming \mutau neutrino oscillation, the angular shape and the normalization factor suggest maximal mixing and \Delta m^2 of a few times 10^{-3} eV^2. Also the other event categories induced by low-energy neutrinos (peak energy ~ 4 GeV) show a deficit of observed events. The value of this deficit and its uniformity with respect to the angular bins are in agreement with the oscillation parameters suggested by the analysis of the upward-throughgoing muon sample.Comment: 13 pages, 9 figures, Proceedings of La Thuile Conferenc

Polarization fields in nitride nanostructures: ten points to think about

Macroscopic polarization, both of intrinsic and piezoelectric nature, is unusually strong in III-V nitrides, and the built in electric fields in the layers of nitride-based nanostructures, stemming from polarization changes at heterointerfaces, have a major impact on the properties of single and multiple quantum wells, high mobility transistors, and thin films. The concepts involved in the theory and applications of polarization in nitrides have encountered some resistance in the field. Here we discuss critically ten ``propositions'' aimed at clarifying the main controversial issues.Comment: RevTeX 5 pages, 2 embedded figure

Dynamical neutrino masses in the generalized Chaplygin gas scenario with mass varying CDM

Neutrinos coupled to an underlying scalar field in the scenario for unification of mass varying dark matter and cosmon-{\em like} dark energy is examined. In the presence of a tiny component of mass varying neutrinos, the conditions for the present cosmic acceleration and for the stability issue are reproduced. It is assumed that {\em sterile} neutrinos behave like mass varying dark matter coupled to mass varying {\em active} neutrinos through the {\em seesaw} mechanism, in a kind of {\em mixed} dark matter sector. The crucial point is that the dark matter mass may also exhibit a dynamical behavior driven by the scalar field. The scalar field mediates the nontrivial coupling between the mixed dark matter and the dark energy responsible for the accelerated expansion of the universe. The equation of state of perturbations reproduce the generalized Chaplygin gas (GCG) cosmology so that all the effective results from the GCG paradigm are maintained, being perturbatively modified by neutrinos.Comment: 19 pages, 5 figure

Relativistic tunneling and accelerated transmission

We obtain the solutions for the tunneling zone of a one-dimensional electrostatic potential in the relativistic (Dirac to Klein-Gordon) wave equation regime when the incoming wave packet exhibits the possibility of being almost totally transmitted through the potential barrier. The conditions for the occurrence of accelerated and, eventually, superluminal tunneling transmission probabilities are all quantified and the problematic superluminal interpretation originated from the study based on non-relativistic dynamics of tunneling is overcome. The treatment of the problem suggests revealing insights into condensed-matter experiments using electrostatic barriers in single- and bi-layer graphene, for which the accelerated tunneling effect deserves a more careful investigation.Comment: 10 pages, 1 figur

The relationship between ILL/document supply and journal subscriptions

Purpose: The purpose of this article is to provide insights into the relationship between ILL/ document supply and journal subscriptions and to assess recent trends in the ILL service. Design/methodology/Approach: This survey is based on data from the ILL service conducted over the five year period 2005-2009 through the Italian NILDE (Network for Inter-Library Document Exchange) network. Findings: This article bears out important previous findings that ILL is not used as a surrogate for journal subscriptions. This is supported by the analysis of a broad number of titles and over a wide time-range. On the contrary, analysis of data transactions, particularly of the most requested journals, can bring about positive effects on new title acquisitions and negotiations with publishers. This paper also shows, at least for Italy, an overall growth and vitality of ILL, in spite of the widespread availability of e-journals acquired through consortia purchasing. Originality/Value: An insight into the relationship between ILL and journal subscriptions in Italy, a country where few studies have been carried out, and none at all for such a large number of libraries and transactions

First-principles calculation of the piezoelectric tensor d of III-V nitrides

We report direct first-principles density-functional calculations of the piezoelectric tensor \tensor{d} relating polarization to applied stress for the binary compounds AlN, GaN, and InN. The values of \tensor{d} are rather sensitive to the choice of the exchange-correlation functional, and results are presented for both the local-density and gradient approximations. A comparison with experiment and with values predicted indirectly from the elastic and e-piezoconstant tensors is also presented.Comment: RevTeX 3 pages, no figure