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G. Salesi

Publications and source records attributed to G. Salesi.

At least 19 recordsLinked to original sources
arXiv2017

Modified Lorentz transformations in deformed special relativity

We extend a recent approach to Deformed Special Relativity based on deformed dispersion laws, entailing modified Lorentz transformations and, at the same time, noncommutative geometry and intrinsically discrete spacetime. In so doing we obtain the explicit form of the modified Lorentz transformations for a special class of modified momentum-energy relations often found in literature and arising from elementary particle physics. Actually, our theory looks as a very simple and natural extension of special relativity to include a momentum cut-off at the Planck scale. In particular, the new Lorentz transformations do imply that for high boost speed ($V \sim c$) the deformed Lorentz factor does not diverge as in ordinary relativity, but results to be upperly bounded by a large finite value of the order of the ratio between the Planck mass and the particle mass. We also predict that a generic boost leaves unchanged Planck energy and momentum, which result invariant with respect to any reference frame.

hep-th↗
arXiv2014

Delayed luminescence induced by complex domains in water and in aqueous solutions

Many recent studies on water have conjectured a complex structure composed of hydrogen bonded low- and high-density domains. In this work the structure of pure water and aqueous solutions of silica gel (TEOS) has been investigated by using delayed luminescence, which previously have showed significant increase in aqueous salt solutions where low-density domain formation is expected. Photon emission shows an Arrhenius trend with an activation energy in water-TEOS solutions larger than in pure water and salt-water solutions. Moreover, delayed photon emission decay shows an intrinsic lifetime of about 5 microseconds both in solutions and in pure water that, along with secondary lifetimes induced by the presence of TEOS, could be related to the formation of different domains.

physics.chem-ph↗
arXiv2013

A new dielectric effect in viscous liquids

An accurate experimental and theoretical study has been performed about a phenomenon, not previously reported in the literature, occurring in highly viscous liquids: the formation of a definite pipe structure induced by the passage of a heavy body, this structure lasting for quite a long time. A very rich phenomenology (including mechanical, optical and structural effects) associated with the formation of the pipe has been observed in different liquids. Actually, the peculiar dynamical evolution of that structure does not appear as a trivial manifestation of standard relaxation or spurious effects. In particular we have revealed different time scales during the evolution of the pipe and a non-monotonous decrease of the persistence time with decreasing viscosity (with the appearance of at least two different maxima). We put forward a microscopic model, consistent with the experimental data, where the pipe behaves as a "dielectric shell" whose time evolution is described through a simple thermodynamical approach, predicting several properties effectively observed.

cond-mat.soft↗
arXiv2013

High sensitivity measurements of thermal properties of textile fabrics

A new testing apparatus is proposed to measure the thermal properties of fabrics made from polymeric materials. The calibration of the apparatus and the data acquisition procedure are considered in detail in order to measure thermal conductivity, resistance, absorption and diffusivity constants of the tested fabric samples. Differences between dry and wet fabrics have been carefully detected and analyzed. We have developed a new measurement protocol, the "ThermoTex" protocol, which agrees with the UNI EN 31092 standard and entails an accurate quantification of the experimental errors according to a standard statistical analysis, thus allowing a rigorous investigation of the physical behavior of the phenomena involved. As a consequence, our machinery exhibits great potentialities for optimizing the thermal comfort of fabrics, according to the market demand, thanks to the possible development of a predictive phenomenological theory of the effects involved.

physics.ins-det↗
arXiv2011

Black hole dynamical evolution in a Lorentz-violating spacetime

We consider the black hole dynamical evolution in the framework of a Lorentz-violating spacetime endowed with a Schwarzchild-like momentum-dependent metric. Large deviations from the Hawking-Bekenstein predictions are obtained, depending on the values of the Lorentz-violating parameter lambda introduced. A non-trivial evolution comes out, following mainly from the existence of a non-vanishing minimum mass: for large Lorentz violations, most of the black hole evaporation takes place in the initial stage, which is then followed by a stationary stage (whose duration depends on the value of lambda) where the mass does not change appreciably. Furthermore, for the final stage of evolution, our model predicts a sweet slow death of the black hole, whose "slowness" again depends on lambda, in contrast with the violent final explosion predicted by the standard theory.

gr-qc↗
arXiv2009

Fundamental times, lengths and physical constants: some unknown contributions by Ettore Majorana

We review the introduction in physics of the concepts of an elementary space length and of a fundamental time scale, analyzing some related unknown contributions by Ettore Majorana. In particular, we discuss the quasi-Coulombian scattering in presence of a finite length scale, as well as the introduction of an intrinsic (universal) time delay in the expressions for the retarded electromagnetic potentials. Finally, we also review a special model considered by Majorana in order to deduce the value of the elementary charge, in such a way anticipating key ideas later introduced in quantum electrodynamics.

physics.hist-ph↗
arXiv2009

CPT-violating neutrino oscillations

We propose a simple phenomenological model predicting, through Lorentz symmetry breaking, a CPT-violating asymmetry between particle and antiparticle states in neutrino oscillations involving sterile neutrinos. Such a model is able to explain the apparently observed anomalous excess of low-energy ν_e-like events, reported by the MiniBooNE collaboration, as well as the non-observation of the corresponding anomalous excess of \ovν_e-like events. The present model leads to very specific physical predictions in the neutrino oscillations scenario, and account for the observed anomalies in terms of only one CPT-Lorentz violation parameter of the order of the Grand-Unification energy scale.

hep-ph↗
arXiv2009

Spin and Madelung fluid

Starting from the Pauli current we obtain the decomposition of the non-relativistic local velocity in two parts: one parallel and the other orthogonal to the momentum. The former is recognized to be the ``classical'' part, that is the velocity of the center-of-mass, and the latter the ``quantum'' one, that is the velocity of the motion in the center-of-mass frame (namely, the internal ``spin motion'' or {\em Zitterbewegung}). Inserting the complete expression of the velocity into the kinetic energy term of the classical non-relativistic (i.e., Newtonian) Lagrangian, we straightforwardly derive the so-called ``quantum potential'' associated to the Madelung fluid. In such a way, the quantum mechanical behaviour of particles appears to be strictly correlated to the existence of spin and Zitterbewegung.

quant-ph↗
arXiv2009

Generalized Ginzburg-Landau models for non-conventional superconductors

We review some recent extensions of the Ginzburg-Landau model able to describe several properties of non-conventional superconductors. In the first extension, s-wave superconductors endowed with two different critical temperatures are considered, their main thermodynamical and magnetic properties being calculated and discussed. Instead in the second extension we describe spin-triplet superconductivity (with a single critical temperature), studying in detail the main predicted physical properties. A thorough discussion of the peculiar predictions of our models and their physical consequences is as well performed.

hep-ph↗
arXiv2009

Describing Sr2RuO4 superconductivity in a generalized Ginzburg--Landau theory

We propose a simple explanation of unconventional thermodynamical and magnetic properties observed for Sr2RuO4. Actually, our two-phase model of superconductivity, based on a straight generalization of the Ginzburg-Landau theory, does predict two jumps in the heat capacity as well as a double curve for the dependence of the critical temperature on an external magnetic field. Such theoretical previsions well agree with the currently available experimental data for Sr2RuO4

cond-mat.supr-con↗
arXiv2009

Black hole evaporation within a momentum-dependent metric

We investigate the black hole thermodynamics in a "deformed" relativity framework where the energy-momentum dispersion law is Lorentz-violating and the Schwarzchild-like metric is momentum-dependent with a Planckian cut-off. We obtain net deviations of the basic thermodynamical quantities from the Hawking-Bekenstein predictions: actually, the black hole evaporation is expected to quit at a nonzero critical mass value (of the order of the Planck mass), leaving a zero temperature remnant, and avoiding a spacetime singularity. Quite surprisingly, the present semiclassical corrections to black hole temperature, entropy, and heat capacity turn out to be identical to the ones obtained within some quantum approaches.

gr-qc↗
arXiv2008

Pipe effect in viscous liquids

A detailed experimental and theoretical study has been performed about a phenomenon, not previously reported in the literature, occurring in highly viscous liquids: the formation of a definite pipe structure induced by the passage of a heavy body, this structure lasting for quite a long time. A very rich phenomenology (including mechanical, optical and structural effects) associated with the formation of the pipe has been observed in different liquids. Actually, the peculiar dynamical evolution of that structure does not appear as a trivial manifestation of standard relaxation or spurious effects. In particular we have revealed different time scales during the evolution of the pipe and a non-monotonous decreasing of the persistence time with decreasing viscosity (with the appearance of at least two different maxima). A microscopic model consistent with the experimental data, where the pipe behaves as a cylindrical dielectric shell, has been proposed. The general time evolution of the structure has been described in terms of a simple thermodynamical model, predicting several peculiarities effectively observed.

physics.chem-ph↗
arXiv2008

Dependence of the critical temperature on the Higgs field reparametrization

We show that, despite of the reparametrization symmetry of the Lagrangian describing the interaction between a scalar field and gauge vector bosons, the dynamics of the Higgs mechanism is really affected by the representation gauge chosen for the Higgs field. Actually, we find that, varying the parametrization for the two degrees of freedom of the complex scalar field, we obtain different expressions for the Higgs mass: in its turn this entails different expressions for the critical temperatures, ranging from zero to a maximum value, as well as different expressions for other basic thermodynamical quantities.

hep-ph↗
arXiv2007

Magnetic properties of two-phase superconductors

We have recently proposed a theoretical model for superconductors endowed with two distinct superconducting phases, described by two scalar order parameters which condensate at different critical temperatures. On analyzing the magnetic behavior of such systems, we have found some observable differences with respect to the case of ordinary Ginzburg-Landau superconductors. In particular, at low temperature the London penetration length is strongly reduced and the Ginzburg-Landau parameter k becomes a function of temperature. By contrast, in the temperature region between the two phase transitions k is constant and the system is a type-I or a type-II superconductor depending on the ratio between the critical temperatures.

cond-mat.supr-con↗
arXiv2007

Second discontinuity in the specific heat of two-phase superconductors

The recently proposed theoretical model of superconductors endowed with two distinct superconducting phases and critical temperatures is further analyzed by introducing two distinct order parameters, described by two scalar fields which condensate at different temperatures. We find some deviations in basic thermodynamical quantities with respect to the Ginzburg-Landau one-phase superconductors. In particular, by contrast to the usual case where only one jump in specific heat takes place at the normal-superconductor transition temperature, we actually predict an additional discontinuity for C_V when passing from a superconducting phase to the other one.

cond-mat.supr-con↗
arXiv2007

Baryon asymmetry in the Universe resulting from Lorentz violation

We analyze the phenomenological consequences of a Lorentz violating energy-momentum dispersion relation in order to give a simple explanation for the baryon asymmetry in the Universe. By assuming very few hypotheses, we propose a straightforward mechanism for generating the observed matter-antimatter asymmetry which entails a Lorentz-breakdown energy scale of the order of the Greisen-Zatsepin-Kuzmin cut-off.

hep-ph↗
arXiv2007

Quantum Lyapunov Exponents

We show that it is possible to associate univocally with each given solution of the time-dependent Schroedinger equation a particular phase flow ("quantum flow") of a non-autonomous dynamical system. This fact allows us to introduce a definition of chaos in quantum dynamics (quantum chaos), which is based on the classical theory of chaos in dynamical systems. In such a way we can introduce quantities which may be appelled "Quantum Lyapunov Exponents". Our approach applies to a non-relativistic quantum-mechanical system of n charged particles; in the present work numerical calculations are performed only for the hydrogen atom. In the computation of the trajectories we first neglect the spin contribution to chaos, then we consider the spin effects in quantum chaos. We show how the quantum Lyapunov exponents can be evaluated and give several numerical results which describe some properties found in the present approach. Although the system is very simple and the classical counterpart is regular, the most non-stationary solutions of the corresponding Schroeodinger equation are "chaotic" according to our definition.

quant-ph↗