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L. Rosa

Publications and source records attributed to L. Rosa.

At least 19 recordsLinked to original sources
arXiv2022

Casimir energy for N superconducting cavities: a model for the YBCO (BSCCO)

In this paper we study the Casimir energy of a sample made by N cavities, with N >> 1, across the transition from the metallic to the superconducting phase of the constituting plates. After having characterized the energy for the configuration in which the layers constituting the cavities are made by dielectric and for the configuration in which the layers are made by plasma sheets, we concentrate our analysis on the latter. It represents the final step towards the macroscopic characterization of a "multi cavity" (with N large) necessary to fully understand the behaviour of the Casimir energy of a YBCO (or a BSCCO) sample across the transition. Our analysis is especially useful to the Archimedes experiment, aimed at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. To this purpose, we aim at modulating the Casimir energy of a layered structure, the multi cavity, by inducing a transition from the metallic to the superconducting phase. After having characterized the Casimir energy of such a structure for both the metallic and the superconducting phase, we give an estimate of the modulation of the energy across the transition.

quant-ph↗
arXiv2020

Numerical investigation of a particle system compared with first and second gradient continua: Deformation and fracture phenomena

A discrete system constituted of particles interacting by means of a centroid-based law is numerically investigated. The elements of the system move in the plane, and the range of the interaction can be varied from a more local form (first-neighbours interaction) up to a generalized nth order interaction. The aim of the model is to reproduce the behaviour of deformable bodies with standard (Cauchy model) or generalized (second gradient) deformation energy density. The numerical results suggest that the considered discrete system can effectively reproduce the behaviour of first and second gradient continua. Moreover, a fracture algorithm is introduced and some comparison between firstand second-neighbour simulations are provided.

cond-mat.soft↗
arXiv2017

Casimir energy for two and three superconducting coupled cavities

In this paper we study the behavior of the Casimir energy of a "multi-cavity" across the transition from the metallic to the superconducting phase of the constituting plates. Our analysis is carried out in the framework of the ARCHIMEDES experiment, aiming at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. For this purpose it is foreseen to modulate the Casimir energy of a layered structure composing a multi-cavity coupled system by inducing a transition from the metallic to the superconducting phase. This implies a thorough study of the behavior of the cavity, where normal metallic layers are alternated with superconducting layers, across the transition. Our study finds that, because of the coupling between the cavities, mainly mediated by the transverse magnetic modes of the radiation field, the variation of energy across the transition can be very large.

hep-th↗
arXiv2017

Double non-perturbative gluon exchange: an update on the soft Pomeron contribution to pp scattering

We employ a set of recent, theoretically motivated, fits to non-perturbative unquenched gluon propagators to check in how far double gluon exchange can be used to describe the soft sector of pp scattering data (total and differential cross section). In particular, we use the refined Gribov--Zwanziger gluon propagator (as arising from dealing with the Gribov gauge fixing ambiguity) and the massive Cornwall-type gluon propagator (as motivated from Dyson-Schwinger equations) in conjunction with a perturbative quark-gluon vertex, next to a model based on the non-perturbative quark-gluon Maris-Tandy vertex, popular from Bethe-Salpeter descriptions of hadronic bound states. We compare the cross sections arising from these models with "older" ISR and more recent TOTEM and ATLAS data. The lower the value of total energy \sqrt{s}, the better the results appear to be.

hep-ph↗
arXiv2015

Effect of the Gribov horizon on the Polyakov loop and vice versa

We consider finite temperature SU(2) gauge theory in the continuum formulation, which necessitates the choice of a gauge fixing. Choosing the Landau gauge, the existing gauge copies are taken into account by means of the Gribov-Zwanziger (GZ) quantization scheme, which entails the introduction of a dynamical mass scale (Gribov mass) directly influencing the Green functions of the theory. Here, we determine simultaneously the Polyakov loop (vacuum expectation value) and Gribov mass in terms of temperature, by minimizing the vacuum energy w.r.t. the Polyakov loop parameter and solving the Gribov gap equation. Inspired by the Casimir energy-style of computation, we illustrate the usage of Zeta function regularization in finite temperature calculations. Our main result is that the Gribov mass directly feels the deconfinement transition, visible from a cusp occurring at the same temperature where the Polyakov loop becomes nonzero. In this exploratory work we mainly restrict ourselves to the original Gribov-Zwanziger quantization procedure in order to illustrate the approach and the potential direct link between the vacuum structure of the theory (dynamical mass scales) and (de)confinement. We also present a first look at the critical temperature obtained from the Refined Gribov-Zwanziger approach. Finally, a particular problem for the pressure at low temperatures is reported.

hep-th↗
arXiv2010

A micro-structured continuum modelling compacting fluid-saturated grounds: the effects of pore-size scale parameter

The effect of a "pore-size" length-scale parameter l on compaction of grounds with fluid inclusions is studied. They are modelled as continua endowed with micro-structure by means of the macro-modelling procedure proposed in [2]. We show the dependence of field evolution equations on the micro-structure parameter l and compare our model with the homogenized asymptotic ones. The consideration of the pore size 1 allows us to forecast the onset of micro-displacement waves as a consequence of a ground settling and to suggest a possible description of the genesis of certain microearthquakes [5] [6].

math-ph↗
arXiv2010

Almansi-type boundary conditions for electric potential inducing flexure in linear piezoelectric beams

Using the recent results found in [1, 2] we prove that it is possible to induce flexur in linear piezoelectric beams by means of quadratic Almansi type boundary conditions for the electric potential. Beams constituted by transversely isotropic piezoelectric materials whose symmetry axis is parallel to the axis of the beam are considered. Our choice of boundary conditions for the electric potential has been suggested by the results found in [1, 3]. An explicit expression of material parameters that influenc flexur is given in terms of piezoelectric moduli.

math-ph↗
arXiv2003

Corsika+Herwig Monte Carlo Simulation of Neutrino Induced Atmospheric Air Showers

High-energy neutrino astronomy represents an open window both on astrophysical mechanisms of particle acceleration and on fundamental interactions. The possibility of detecting them in large earth-based apparatus, like AUGER, AMANDA, ANTARES, is quite challenging. In view of this, the capability of generating reliable simulations of air showers induced by neutrinos is mandatory in the analysis of experimental data. In this paper we describe preliminary results towards the development of a new version of the Monte Carlo CORSIKA, capable of handling neutrinos too as primary particles. In our approach the first interaction of the primary neutrino is simulated in CORSIKA with a call to the HERWIG event generator.

astro-ph↗
arXiv2002

Critical exponents of the Gross-Neveu model from the effective average action

The phase transition of the Gross-Neveu model with N fermions is investigated by means of a non-perturbative evolution equation for the scale dependence of the effective average action. The critical exponents and scaling amplitudes are calculated for various values of N in d=3. It is also explicitely verified that the Neveu-Yukawa model belongs to the same universality class as the Gross-Neveu model.

hep-th↗
arXiv2000

The Strange Quark Problem in the Framework of Statistical Distributions

A large class of polarized and unpolarized deep inelastic data is successfully described with Fermi-Dirac functions for the non-diffractive part of quark parton distributions. The NLO approach used here improves the agreement with experiment of the previous LO work. We get a broader distribution for the strange parton s(x) than for sbar(x).

hep-ph↗
arXiv1998

Probability representation in quantum field theory

The recently proposed probability representation of quantum mechanics is generalized to quantum field theory. We introduce a probability distribution functional for field configurations and find an evolution equation for such a distribution. The connection to the time-dependent generating functional of Green's functions is elucidated and the classical limit is discussed.

hep-th↗
arXiv1998

Renormalization Group Naturalness of GUT Higgs Potentials

We analyze the symmetry-breaking patterns of grand unified theories from the point of view of a recently-proposed criterion of renormalization-group naturalness. We perform the analysis on simple non-SUSY SU(5) and SO(10) and SUSY SU(5) GUTs. We find that the naturalness criterion can favor spontaneous-symmetry-breaking in the direction of the smallest of the maximal little groups. Some differences between theories with and without supersymmetry are also emphasized.

hep-ph↗
arXiv1998

A Positive Test for Fermi-Dirac Distributions of Quark-Partons

By describing a large class of deep inelastic processes with standard parameterization for the different parton species, we check the characteristic relationship dictated by Pauli principle: broader shapes for higher first moments. Indeed, the ratios between the second and the first moment and the one between the third and the second moment for the valence partons is an increasing function of the first moment and agrees quantitatively with the values found with Fermi-Dirac distributions.

hep-ph↗
arXiv1998

Time-Dependent Invariants and Green's Functions in the Probability Representation of Quantum Mechanics

In the probability representation of quantum mechanics, quantum states are represented by a classical probability distribution, the marginal distribution function (MDF), whose time dependence is governed by a classical evolution equation. We find and explicitly solve, for a wide class of Hamiltonians, new equations for the Green's function of such an equation, the so-called classical propagator. We elucidate the connection of the classical propagator to the quantum propagator for the density matrix and to the Green's function of the Schrödinger equation. Within the new description of quantum mechanics we give a definition of coherence solely in terms of properties of the MDF and we test the new definition recovering well known results. As an application, the forced parametric oscillator is considered . Its classical and quantum propagator are found, together with the MDF for coherent and Fock states.

quant-ph↗
arXiv1997

Quantum singular oscillator as a model of two-ion trap: an amplification of transition probabilities due to small time variations of the binding potential

Following the paper by M. Combescure [Ann. Phys. (NY) 204, 113 (1990)], we apply the quantum singular time dependent oscillator model to describe the relative one dimensional motion of two ions in a trap. We argue that the model can be justified for low energy excited states with the quantum numbers $n\ll n_{max}\sim 100$, provided that the dimensionless constant characterizing the strength of the repulsive potential is large enough, $g_*\sim 10^5$. Time dependent Gaussian-like wave packets generalizing odd coherent states of the harmonic oscillator, and excitation number eigenstates are constructed. We show that the relative motion of the ions, in contradistinction to its center of mass counterpart, is extremely sensitive to the time dependence of the binding harmonic potential, since the large value of $g_*$ results in a significant amplification of the transition probabilities between energy eigenstate even for slow time variations of the frequency.

quant-ph↗
arXiv1997

Limits on Neutrino Masses in SO(10) GUT's

Studying Renormalization Group Equations for the four typical SO(10) spontaneous symmetry breaking patterns we find the existence of lower limits on neutrino masses.

hep-ph↗
arXiv1997

SO(10) Unified Theories and Cosmology

We review the status of a class of gauge unified models based on SO(10) group. After a pedagogical introduction to SO(10) gauge theories, we discuss the main phenomenological implications of these models. The upper limit on proton lifetime are obtained and the prediction for neutrino masses are compared with the astrophysical and cosmological constraints coming from solar neutrino data and dark matter problem. Possible scenarios for the production of the baryon asymmetry of the universe required by primordial nucleosynthesis are also discussed.

hep-ph↗