The Nambu-Jona Lasinio mechanism and the electroweak symmetry breaking in the Standard Model

This is a short report of the entire work developed during the study of the possible realizations of the "Top Mode" Standard Model. Here it is examined the breaking of internal symmetries from another point of view showing that is possible to reproduce the gauged electroweak panorama of the traditional Standard Model in a exhaustive and selfconsistent way. The result is reached applying the main futures of the Nambu-Jona Lasinio (NJL) mechanism to an electroweak invariant Lagrangian. In this context the use of functional formalism for composite operators naturally leads to a different dynamical approach. Meanwhile the Higgs mechanism acts on the Lagrangian form, a NJL like model looks directly at the physics of the system showing the real dynamical content hidden in the Green functions of the theory.Comment: 18 Pages, no figures, LaTex, corrected typos, references remove

Block Iterative Eigensolvers for Sequences of Correlated Eigenvalue Problems

In Density Functional Theory simulations based on the LAPW method, each self-consistent field cycle comprises dozens of large dense generalized eigenproblems. In contrast to real-space methods, eigenpairs solving for problems at distinct cycles have either been believed to be independent or at most very loosely connected. In a recent study [7], it was demonstrated that, contrary to belief, successive eigenproblems in a sequence are strongly correlated with one another. In particular, by monitoring the subspace angles between eigenvectors of successive eigenproblems, it was shown that these angles decrease noticeably after the first few iterations and become close to collinear. This last result suggests that we can manipulate the eigenvectors, solving for a specific eigenproblem in a sequence, as an approximate solution for the following eigenproblem. In this work we present results that are in line with this intuition. We provide numerical examples where opportunely selected block iterative eigensolvers benefit from the reuse of eigenvectors by achieving a substantial speed-up. The results presented will eventually open the way to a widespread use of block iterative eigensolvers in ab initio electronic structure codes based on the LAPW approach.Comment: 12 Pages, 5 figures. Accepted for publication on Computer Physics Communication

Multiparametric Quantum Algebras and the Cosmological Constant

With a view towards applications for de Sitter, we construct the multi-parametric $q$-deformation of the so(5,\IC) algebra using the Faddeev-Reshetikhin-Takhtadzhyan (FRT) formalism.Comment: v4: cosmetic changes from the published versio

Correlated dynamics of water and amphiphilic molecules in thin Newton black films

The dynamical properties of amphiphilics in Newton black films, as well as those of the water confined between the two charged hydrophilic surfaces, have been calculated via a series of molecular dynamic calculations in several films with different water content. A charged semi-flexible amphiphilic model and the TIP5P model of water are used in our simulations [J. Chem. Phys. 129, 164901 (2008)]. We calculate the diffusion coefficients, reorientational dynamics and the atomic density profile of water molecules as a function of the number of water molecules per amphiphilic (nw). We also analyse the reorientational motion of the amphiphilics and  determine a strong correlation between the dynamics of water molecules and the translational and reorientational dynamics of the amphiphilics, as well as a correlation between the reorientational dynamics of the amphiphilics belonging to the  upper and lower halves of the studied thin films.Fil: Di Napoli, Solange Mariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Gamba, Z.. Comisión Nacional de Energía Atómica; Argentin

The Trigger System of the ARGO-YBJ detector

The ARGO-YBJ experiment has been designed to detect air shower events over a large size scale and with an energy threshold of a few hundreds GeV. The building blocks of the ARGO-YBJ detector are single-gap Resistive Plate Counters (RPCs). The trigger logic selects the events on the basis of their hit multiplicity. Inclusive triggers as well as dedicated triggers for specific physics channels or calibration purposes have been developed. This paper describes the architecture and the main features of the trigger system.Comment: 4 pages, to be published in the Proceedings of the 28th International Cosmic Ray Conference (Tsukuba, Japan 2003

Families and Social Media Use: The Role of Parents' Perceptions about Social Media Impact on Family Systems in the Relationship between Family Collective Efficacy and Open Communication

Communication through social media characterizes modern lifestyles and relationships, including family interactions. The present study aims at deepening the role that parents’ perceptions about social media effects on family systems can exert within their family functioning, specifically referring to the relationship between collective family efficacy and open communications within family systems with adolescents. A questionnaire to detect the openness of family communications, thecollectivefamilyefficacyandtheperceptionsabouttheimpactsofsocialmediaonfamilysystems wasadministeredto227Italianparentswhohadoneormoreteenagechildren,andwhouseFacebook and WhatsApp to communicate with them. From the results, these perceptions emerge as a mediator in the relationship between the collective family efficacy and the openness of communications, suggestingthatitisnotonlytheactualimpactofsocialmediaonfamilysystemsthatmattersbutalso parents’ perceptions about it and how much they feel able to manage their and their children’s social media use without damaging their family relationships. Thus, the need to foster parents’ positive perceptions about social media’s potential impact on their family relationships emerges. A strategy could be the promotion of knowledge on how to functionally use social media

An Optimized and Scalable Eigensolver for Sequences of Eigenvalue Problems

In many scientific applications the solution of non-linear differential equations are obtained through the set-up and solution of a number of successive eigenproblems. These eigenproblems can be regarded as a sequence whenever the solution of one problem fosters the initialization of the next. In addition, in some eigenproblem sequences there is a connection between the solutions of adjacent eigenproblems. Whenever it is possible to unravel the existence of such a connection, the eigenproblem sequence is said to be correlated. When facing with a sequence of correlated eigenproblems the current strategy amounts to solving each eigenproblem in isolation. We propose a alternative approach which exploits such correlation through the use of an eigensolver based on subspace iteration and accelerated with Chebyshev polynomials (ChFSI). The resulting eigensolver is optimized by minimizing the number of matrix-vector multiplications and parallelized using the Elemental library framework. Numerical results show that ChFSI achieves excellent scalability and is competitive with current dense linear algebra parallel eigensolvers.Comment: 23 Pages, 6 figures. First revision of an invited submission to special issue of Concurrency and Computation: Practice and Experienc

An Example of Symmetry Exploitation for Energy-related Eigencomputations

One of the most used approaches in simulating materials is the tight-binding approximation. When using this method in a material simulation, it is necessary to compute the eigenvalues and eigenvectors of the Hamiltonian describing the system. In general, the system possesses few explicit symmetries. Due to them, the problem has many degenerate eigenvalues. The ambiguity in choosing a orthonormal basis of the invariant subspaces, associated with degenerate eigenvalues, will result in eigenvectors which are not invariant under the action of the symmetry operators in matrix form. A meaningful computation of the eigenvectors needs to take those symmetries into account. A natural choice is a set of eigenvectors, which simultaneously diagonalizes the Hamiltonian and the symmetry matrices. This is possible because all the matrices commute with each other. The simultaneous eigenvectors and the corresponding eigenvalues will be in a parametrized form in terms of the lattice momentum components. This functional dependence of the eigenvalues is the dispersion relation and describes the band structure of a material. Therefore it is important to find this functional dependence in any numerical computation related to material properties.Comment: To appear in the proceedings of the 7th International Conference on Computational Methods in Science and Engineering (ICCMSE '09

Mean radiant temperature from global-scale numerical weather prediction models

In human biometeorology, the estimation of mean radiant temperature (MRT) is generally considered challenging. This work presents a general framework to compute the MRT at the global scale for a human subject placed in an outdoor environment and irradiated by solar and thermal radiation both directly and diffusely. The proposed framework requires as input radiation fluxes computed by numerical weather prediction (NWP) models and generates as output gridded globe-wide maps of MRT. It also considers changes in the Sun’s position affecting radiation components when these are stored by NWP models as an accumulated-over-time quantity. The applicability of the framework was demonstrated using NWP reanalysis radiation data from the European Centre for Medium-Range Weather Forecasts. Mapped distributions of MRT were correspondingly computed at the global scale. Comparison against measurements from radiation monitoring stations showed a good agreement with NWP-based MRT (coefficient of determination greater than 0.88; average bias equal to 0.42 °C) suggesting its potential as a proxy for observations in application studies