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C. Providencia

Publications and source records attributed to C. Providencia.

At least 37 records · Page 2Linked to original sources
arXiv2013

Interplay between Spin Polarization and Color Superconductivity in High Density Quark Matter

Here, it is suggested that a four-point interaction of the tensor type may lead to spin polarization in quark matter at high density. It is found that the two-flavor superconducting phase and the spin polarized phase correspond to distinct local minima of a certain generalized thermodynamical potential. It follows that the transition from one to the other phase occurs passing through true minima with both a spin polarization and a color superconducting gap. It is shown that the quark spin polarized phase is realized at rather high density, while the two-flavor color superconducting phase is realized at a lower density region.

nucl-th↗
arXiv2013

A Pseudo su(1,1)-Algebraic Deformation of the Cooper-Pair in the su(2)-Algebraic Many-Fermion Model

A pseudo su(1,1)-algebra is formulated as a possible deformation of the Cooper-pair in the su(2)-algebraic many-fermion system. With the aid of this algebra, it is possible to describe behavior of individual fermions which are generated as the result of interaction with the external environment. The form presented in this paper is a generalization of a certain simple case developed recently by the present authors. Basic idea follows the su(1,1)-algebra in the Schwinger boson representation for treating energy transfer between the harmonic oscillator and the external environment. Hamiltonian is given under the idea of the phase space doubling in the thermo-field dynamics formalism and the time-dependent variational method is applied to this Hamiltonian. Its trial state is constructed in the frame deformed from the BCS-Bogoliubov approach to the superconductivity. Several numerical results are shown.

nucl-th↗
arXiv2012

Quark-Hadron Phase-Transition in an Extended NJL Model with Scalar-Vector Interaction

The quark-hadron phase transition at finite temperature and baryon chemical potential is investigated in an extended NJL model with scalar-vector eight-point interaction by comparing the pressure of symmetric nuclear matter with that of the quark matter. As a result, the extended NJL phase diagram is obtained in the temperature-baryon chemical potential plane and the effects of the scalar-vector coupling constant G_{sv}^q on the chiral phase transition are summarized. It is shown that a quarkyonic-like phase in which the chiral symmetry is restored but the elementary excitation modes are nucleonic appears just before deconfinement in this model.

hep-ph↗
arXiv2012

Effective Potential Approach to Quark Ferromagnetization in High Density Quark Matter

A possibility of spontaneous magnetization in high density symmetric quark matter is investigated using the NJL type effective model of QCD by means of an effective potential with respect to an auxiliary field. It is shown that the quark ferromagnetic condensate has non-vanishing value at high baryon density due to the tensor-type four-point interaction between quarks.

nucl-th↗
arXiv2012

The BCS-Bogoliubov and the su(2)-Algebraic Approach to the Pairing Model in Many-Fermion System

The relation between two approaches to the su(2)-algebraic many-fermion model is discussed: (1) the BCS-Bogoliubov approach in terms of the use of the quasiparticles representing all the degrees of freedom except those related to the Cooper-pairs and (2) the conventional algebraic approach in terms of the use of the minimum weight states, from which the Cooper-pairs are excluded. In order to arrive at the goal, the idea of the quasiparticles is brought up in the conservation of the fermion number. Under the c-number replacement for the three su(2)-generators, the quasiparticles suggested in this paper are reduced to those in the BCS-Bogoliubov approach. It is also shown that the two approaches are equivalent through the c-number replacement. Further, a certain modification of the BCS-Bogoliubov approach is discussed.

nucl-th↗
arXiv2012

A Role of the Quasiparticle in the Conservation of the Fermion Number

The role of the "quasiparticle" introduced in last paper by the present authors is discussed. It serves as a guide for the deformation of the Cooper-pair in the BCS-Bogoliubov approach. As an illustrative example, a certain case is treated. This case produces the su(1,1)-like behavior in the su(2)-algebraic many-fermion system.

nucl-th↗
arXiv2012

Color-Singlet Three-Quark States in the su(4)-Algebraic Many-Quark Model

As announced in last paper by the present authors, the color-singlet three-quark states are investigated for the case of the spherical j-j coupling and L-S coupling shell models. The latter case automatically leads to the su(4)*su(4)-model. For a certain type of Hamiltonian, the states of individual "nucleons" are characterized.

hep-ph↗
arXiv2011

Note on the Minimum Weight States in the su(2)-Algebraic Many-Fermion Model --- Extension of the Role of the Auxiliary su(2)-Algebra ---

The role of the auxiliary su(2)-algebra proposed by the present authors in the latest paper is extended. Its aim is to determine the minimum weight states completely. With the aid of scalar operators for the auxiliary algebra, new aspects are added to the minimum weight states in the aligned scheme discussed in the latest paper. Some simple examples are shown.

nucl-th↗
arXiv2011

Background of the su(2)-Algebraic Many-Fermion Models in the Boson Realization

The su(2)-algebraic many-fermion model is formulated so as to be able to get the unified understanding of the structures of three simple models: the single-level pairing, the isoscalar proton-neutron pairing and the two-level Lipkin model. Basic idea is to introduce an auxiliary su(2)-algebra, any generator of which commutes with any generator of the starting su(2)-algebra. With the aid of this algebra, the minimum weight states are completely determined in a simple forms. Further, concerning the two algebras, boson realization is presented. Through this formulation, the behavior of the total fermion in the Lipkin model is notably different of those in the other two models. As supplementary problem, the boson-fermion realization and the Lipkin model in the isovector pairing model are investigated.

nucl-th↗
arXiv2011

On the Color-Singlet States in Many-Quark Model with the su(4)-Algebraic Structure. II

Ground-state energies are investigated in a many-quark model with pairing interactions, which has the su(4)-algebraic structure. Exact eigenstates in the boson realization method are constructed by imposing a color-singlet condition developed in the previous paper. An interaction term breaking the su(4)-dynamical symmetry plays an important role to determine the ground state. As a result, a quark-pairing state or a quark-triplet state as a nucleon is realized with a certain value of a variable which is regarded as an order parameter. In addition to the parameter regions in which these ground states are realized, it is shown that there are two transition regions between the quark-pairing and the quark-triplet states with different values of the order parameter.

nucl-th↗
arXiv2011

On the Color-Singlet States in Many-Quark Model with the su(4)-Algebraic Structure. III

A phase structure and phase transitions are investigated in the modified Bonn quark model. The force strength, which represents the particle-hole type interaction, is devised so as to depend on the quark number, namely quark number density. As a result, it is shown that the phase transition from the quark-triplet state as a nucleon to the quark-pair state as a color-superconducting state occurs as the density increases.

nucl-th↗
arXiv2011

Landau parameters for asymmetric nuclear matter with a strong magnetic field

The Landau Fermi Liquid parameters are calculated for charge neutral asymmetric nuclear matter in beta equilibrium at zero temperature in the presence of a very strong magnetic field with relativistic mean-field models. Due to the isospin structure of the system, with different populations of protons and neutrons and spin alignment to the field, we find non-vanishing Landau mixing parameters. The existence of quantized Landau levels for the charged sector has some impact on the Landau parameters with the presence of discretized features in those involving the proton sector. Using the Fermi liquid formalism singlet and triplet excited quasiparticle states are analyzed, and we find that in-medium effects and magnetic fields are competing, however, the former are more important in the interaction energy range considered. It is found that for magnetic field strengths Log$_{10}$ B (G) $\le 17$ the relative low polarization of the system produces mild changes in the generalized Landau parameters with respect to the unmagnetized case, while for larger strengths there is a resolution of the degeneracy of the interaction energies of quasiparticles in the system.

nucl-th↗
arXiv2010

Two-Level Lipkin Model in Unconventional Boson Realization

With the aim of applying to the Lipkin model in the case of open shell system, a possible form of the boson realization for the su(2)-algebra is proposed both in the Schwinger and the Holstein-Primakoff representation. The basic idea is borrowed from the Schwinger boson realization for the su(4)-algebra for many-quark system recently presented by the present authors. As the simplest approximation, a certain approximate form is given and the result is a natural generalization of the RPA result in the case of closed shell system.

nucl-th↗
arXiv2010

New theorem of classical electromagnetism: equilibrium magnetic field and current density are zero inside ideal conductors

We prove a theorem on the magnetic energy minimum in a system of perfect, or ideal, conductors. It is analogous to Thomson's theorem on the equilibrium electric field and charge distribution in a system of conductors. We first prove Thomson's theorem using a variational principle. Our new theorem is then derived by similar methods. We find that magnetic energy is minimized when the current distribution is a surface current density with zero interior magnetic field; perfect conductors are perfectly diamagnetic. The results agree with currents in superconductors being confined near the surface. The theorem implies a generalized force that expels current and magnetic field from the interior of a conductor that loses its resistivity. Examples of solutions that obey the theorem are presented.

physics.class-ph↗
arXiv2010

First Order Quark-Hadron Phase Transition in the NJL-Type Nuclear and Quark Model

The quark-hadron phase transition at finite baryon chemical potential is investigated in the extended Nambu-Jona-Lasinio model in which the scalar-vector eight-point interaction is included holding the chiral symmetry. By comparing a pressure of the symmetric nuclear matter with that of the quark matter, the realized phase at given baryon density is determined. As a result, the first order quark-hadron phase transition is derived where the deconfinement transition occurs after the chiral symmetry restoration in this model.

hep-ph↗
arXiv2009

Minimum magnetic energy theorem predicts Meissner effect in perfect conductors

A theorem on the magnetic energy minimum in a perfect, or ideal, conductor is proved. Contrary to conventional wisdom the theorem provides a classical explanation of the expulsion of a magnetic field from the interior of a conductor that loses its resistivity. It is analogous to Thomson's theorem which states that static charge distributions in conductors are surface charge densities at constant potential since these have minimum energy. This theorem is proved here using a variational principle. Then an analogous result for the magnetic energy of current distributions is proved: magnetic energy is minimized when the current distribution is a surface current density with zero interior magnetic field. The result agrees with currents in superconductors being confined near the surface and indicates that the distinction between superconductors and hypothetical perfect conductors is artificial.

cond-mat.supr-con↗