arXiv subjects

A. Lavagno

Publications and source records attributed to A. Lavagno.

At least 37 records · Page 2Linked to original sources

arXiv2009

Intermediate statistics as a consequence of deformed algebra

We present a formulation of the deformed oscillator algebra which leads to intermediate statistics as a continuous interpolation between the Bose-Einstein and Fermi-Dirac statistics. It is deduced that a generalized permutation or exchange symmetry leads to the introduction of the basic number and it is then established that this in turn leads to the deformed algebra of oscillators. We obtain the mean occupation number describing the particles obeying intermediate statistics which thus establishes the interpolating statistics and describe boson like and fermion like particles obeying intermediate statistics. We also obtain an expression for the mean occupation number in terms of an infinite continued fraction, thus clarifying successive approximations.

cond-mat.stat-mech↗

arXiv2009

Basic-deformed quantum mechanics

Starting on the basis of $q$-symmetric oscillator algebra and on the associate $q$-calculus properties, we study a deformed quantum mechanics defined in the framework of the basic square-integrable wave functions space. In this context, we introduce a deformed Schroedinger equation, which satisfies the main quantum mechanics assumptions and admits, in the free case, plane wave functions that can be expressed in terms of the q-deformed exponential, originally introduced in the framework of the basic-hypergeometric functions.

math-ph↗

arXiv2009

Non-extensive statistical effects in high-energy collisions

Following the basic prescriptions of the relativistic Tsallis' non-extensive thermostatistics, we investigate from a phenomenological point of view the relevance of non-extensive statistical effects on relativistic heavy-ion collisions observable, such as rapidity spectra of net proton production, transverse momentum distributions and transverse momentum fluctuations. Moreover, we study the nuclear and the subnuclear equation of state, investigating the critical densities of a phase transition to a hadron-quark-gluon mixed phase by requiring the Gibbs conditions on the global conservation of the electric and the baryon charges. The relevance of small deviations from the standard extensive statistics is studied in the context of intermediate and high energy heavy-ion collisions.

nucl-th↗

arXiv2008

Deformed quantum mechanics and q-Hermitian operators

Starting on the basis of the non-commutative q-differential calculus, we introduce a generalized q-deformed Schrödinger equation. It can be viewed as the quantum stochastic counterpart of a generalized classical kinetic equation, which reproduces at the equilibrium the well-known q-deformed exponential stationary distribution. In this framework, q-deformed adjoint of an operator and q-hermitian operator properties occur in a natural way in order to satisfy the basic quantum mechanics assumptions.

math-ph↗

arXiv2008

Deformed quantum statistics in two-dimensions

It is known from the early work of May in 1964 that ideal Bose gas do not exhibit condensation phenomenon in two dimensions. On the other hand, it is also known that the thermostatistics arising from q-deformed oscillator algebra has no connection with the spatial dimensions of the system. Our recent work concerns the study of important thermodynamic functions such as the entropy, occupation number, internal energy and specific heat in ordinary three spatial dimensions, where we established that such thermostatistics is developed by consistently replacing the ordinary thermodynamic derivatives by the Jackson derivatives. The thermostatistics of q-deformed bosons and fermions in two spatial dimensions is an unresolved question and that is the subject of this investigation. We study the principal thermodynamic functions of both bosons and fermions in the two dimensional q-deformed formalism and we find that, different from the standard case, the specific heat of q-boson and q-fermion ideal gas, at fixed temperature and number of particle, are no longer identical.

cond-mat.stat-mech↗

arXiv2007

Basic-deformed thermostatistics

Starting from the basic-exponential, a q-deformed version of the exponential function established in the framework of the basic-hypergeometric series, we present a possible formulation of a generalized statistical mechanics. In a q-nonuniform lattice we introduce the basic-entropy related to the basic-exponential by means of a q-variational principle. Remarkably, this distribution exhibits a natural cut-off in the energy spectrum. This fact, already encountered in other formulations of generalized statistical mechanics, is expected to be relevant to the applications of the theory to those systems governed by long-range interactions. By employing the q-calculus, it is shown that the standard thermodynamic functional relationships are preserved, mimicking, in this way, the mathematical structure of the ordinary thermostatistics which is recovered in the q=1 limit.

cond-mat.stat-mech↗

arXiv2006

Signals of non-extensive statistical mechanics in high-energy nuclear collisions

Starting from the presence of non-ideal plasma effects due to strongly coupled plasma in the early stage of relativistic heavy-ion collisions, we investigate, from a phenomenological point of view, the relevance of non-conventional statistical mechanics effects on the rapidity spectra of net proton yield at AGS, SPS and RHIC. We show that the broad rapidity shape measured at RHIC can be very well reproduced in the framework of a non-linear relativistic Fokker-Planck equation which incorporates non-extensive statistics and anomalous diffusion.

hep-ph↗

arXiv2006

Classical and quantum q-deformed physical systems

On the basis of the non-commutative q-calculus, we investigate a q-deformation of the classical Poisson bracket in order to formulate a generalized q-deformed dynamics in the classical regime. The obtained q-deformed Poisson bracket appears invariant under the action of the q-symplectic group of transformations. In this framework we introduce the q-deformed Hamilton's equations and we derive the evolution equation for some simple q-deformed mechanical systems governed by a scalar potential dependent only on the coordinate variable. It appears that the q-deformed Hamiltonian, which is the generator of the equation of motion, is generally not conserved in time but, in correspondence, a new constant of motion is generated. Finally, by following the standard canonical quantization rule, we compare the well known q-deformed Heisenberg algebra with the algebra generated by the q-deformed Poisson bracket.

quant-ph↗

arXiv2006

Testing Deconfinement at High Isospin Density

We study the transition from hadronic matter to a mixed phase of quarks and hadrons at high baryon and isospin densities reached in heavy ion collisions. We focus our attention on the role played by the nucleon symmetry energy at high density.In this respect the inclusion of a scalar isovector meson, the δ-coupling, in the Hadron Lagrangian appears rather important. We study in detail the formation of a drop of quark matter in the mixed phase, and we discuss the effects on the quark drop nucleation probability of the finite size and finite time duration of the high density region. We find that, if the parameters of quark models are fixed so that the existence of quark stars is allowed, then the density at which a mixed phase starts forming drops dramatically in the range Z/A \sim 0.3--0.4. This opens the possibility to verify the Witten-Bodmer hypothesis on absolute stability of quark matter using ground-based experiments in which neutron-rich nuclei are employed. These experiments can also provide rather stringent constraints on the Equation of State (EoS) to be used for describing the pre-Supernova gravitational collapse. Consistent simulations of neutron rich heavy ion collisions are performed in order to show that even at relatively low energies, in the few AGeV range, the system can enter such unstable mixed phase. Some precursor observables are suggested, in particular a ``neutron trapping'' effect.

nucl-th↗

arXiv2005

Classical q-deformed dynamics

On the basis of the quantum q-oscillator algebra in the framework of quantum groups and non-commutative q-differential calculus, we investigate a possible q-deformation of the classical Poisson bracket in order to extend a generalized q-deformed dynamics in the classical regime. In this framework, classical q-deformed kinetic equations, Kramers and Fokker-Planck equations, are also studied. Pacs: 05.20.Dd, 45.20.-d, 02.20.Uw Keywords: Kinetic theory, q-deformed classical mechanics, quantum groups, quantum algebras

cond-mat.stat-mech↗

arXiv2005

Bulk Viscosity in Hybrid Stars

We compute the bulk viscosity of a mixed quark-hadron phase. In the first scenario to be discussed, the mixed phase occurs at large densities and we assume that it is composed of a mixing of hyperonic matter and quarks in the Color Flavor Locked phase. In a second scenario, the mixed phase occurs at lower densities and it is composed of a mixing of nucleons and unpaired quark matter. We have also investigated the effect of a non-vanishing surface tension at the interface between hadronic and quark matter. In both scenarios, the bulk viscosity is large when the surface tension is absent, while the value of the viscosity reduces in the second scenario when a finite value for the surface tension is taken into account. In all cases, the r-mode instabilities of the corresponding hybrid star are suppressed.

astro-ph↗

arXiv2005

q-deformed structures and generalized thermodynamics

On the basis of the recently proposed formalism [A. Lavagno and P.N. Swamy, Phys. Rev. E 65, 036101 (2002)], we show that the realization of the thermostatistics of q-deformed algebra can be built on the formalism of q-calculus. It is found that the entire structure of thermodynamics is preserved if we use an appropriate Jackson derivative instead of the ordinary thermodynamic derivative. Furthermore, in analogy with the quantum q-oscillator algebra, we also investigate a possible q-deformation of the classical Poisson bracket in order to extend a generalized q-deformed dynamics in the classical regime.

cond-mat.stat-mech↗

arXiv2005

Nonextensive statistical effects on nuclear astrophysics and many-body problems

Density and temperature conditions in many stellar core (like the solar core) imply the presence of nonideal plasma effects with memory and long-range interactions between particles. This aspect suggests the possibility that the stellar core could not be in a global thermodynamical equilibrium but satisfies the conditions of a metastable state with a stationary (nonextensive) power law distribution function among ions. The order of magnitude of the deviation from the standard Maxwell-Boltzmann distribution can be derived microscopically by considering the presence of random electrical microfields in the stellar plasma. We show that such a nonextensive statistical effect can be very relevant in many nuclear astrophysical problems.

nucl-th↗

arXiv2005

Gapless color-flavor locked phase in quark and hybrid stars

We study the effects of the gapless color-flavor locked (gCFL) phase on the equation of state of strongly interacting matter in the range of baryonic chemical potential involved in a compact star. We analyze the possibility of a phase transition from hadronic matter to gCFL quark matter and we discuss, for different values of the strange quark mass and diquark coupling strength, the existence of a gCFL phase in quark or hybrid stars. The mass-radius relation and the structure of compact stars containing the gCFL phase are shown and the physical relevance of this superconducting phase inside a stellar object is also discussed.

nucl-th↗

arXiv2005

Metastable and stable equilibrium states of stellar electron-nuclear plasmas

By minimizing free energy density, we show that the stellar core of a hydrogen burning star is not in a global thermodynamical equilibrium unless density, temperature, mass and composition assume given values. The core (as the solar interior) may be viewed more appropriately as a metastable state with very long lifetime. Slightly non-extensive distribution function could be the natural distribution for a weakly non-ideal plasma like a stellar core and represents a more appropriate approximation to this system than a Maxwellian distribution, without affecting bulk properties of stars.

nucl-th↗

arXiv2004

Effects of color superconductivity on the structure and formation of compact stars

We show that if color superconducting quark matter forms in hybrid or quark stars it is possible to satisfy most of recent observational boundaries on masses and radii of compact stellar objects. An energy of the order of $10^{53}$ erg is released in the conversion from a (metastable) hadronic star into a (stable) hybrid or quark star in presence of a color superconducting phase. If the conversion occurs immediately after the deleptonization of the proto-neutron star, the released energy can help Supernovae to explode. If the conversion is delayed the energy released can power a Gamma Ray Burst. A delay between the Supernova and the subsequent Gamma Ray Burst is possible, in agreement with the delay proposed in recent analysis of astrophysical data.

nucl-th↗

arXiv2003

Temperature dependence of modified CNO nuclear reaction rates in dense stellar plasmas

We study the dependence of the CNO nuclear reaction rates on temperature, in the range of $10^7÷10^8$ K, the typical range of temperature evolution from a Sun-like star towards a white dwarf. We show that the temperature dependence of the CNO nuclear reaction rates is strongly affected by the presence of non-extensive statistical effects in the dense stellar core. A very small deviation from the Maxwell-Boltzmann particle distribution implies a relevant enhancement of the CNO reaction rate and could explain the presence of heavier elements (e.g. Fe, Mg) in the final composition of a white dwarf core. Such a behavior is consistent with the recent experimental upper limit to the fraction of energy that the Sun produces via the CNO fusion cycle.

nucl-th↗

arXiv2003

Nonextensive statistical effects on the relativistic nuclear equation of state

Following the basic prescriptions of the Tsallis' nonextensive thermodynamics, we study the relativistic nonextensive thermodynamics and the equation of state for a perfect gas at the equilibrium. The obtained results are used to study the relativistic nuclear equation of state in the hadronic and in the quark-gluon plasma phase. We show that small deviations from the standard extensive statistics imply remarkable effects into the shape of the equation of state.

nucl-th↗