arXiv subjects

S. Cruz-Barrios

Publications and source records attributed to S. Cruz-Barrios.

7 recordsLinked to original sources

arXiv2019

Analysis of quasielastic $(e,e')$ electromagnetic responses and scaling for nuclear matter in the relativistic mean field model

A detailed study of the electromagnetic responses for quasielastic $(e,e')$ reactions from nuclear matter is presented within the framework of a relativistic model including momentum dependent scalar and vector mean field potentials in both the initial and final nucleon wave function states. The effects ascribed to the use of energy-dependent potentials are carefully analyzed by comparing their predictions with the responses obtained in the case of constant, i.e., energy-independent, potentials, as well as with the plane wave limit in the final state. The study is extended to the scaling phenomenon. Results are provided for the scaling functions corresponding to different nuclear systems evaluated at several kinematics ranging from intermediate to high values of the transfer momentum. Emphasis is placed on scaling of the first and second kinds and the role played by the relativistic scalar and vector mean field potentials.

nucl-th↗

arXiv2004

Quantum mechanical description of Stern-Gerlach experiments

The motion of neutral particles with magnetic moments in an inhomogeneous magnetic field is described in a quantum mechanical framework. The validity of the semi-classical approximations which are generally used to describe these phenomena is discussed. Approximate expressions for the evolution operator are derived and compared to the exact calculations. Focusing and spin-flip phenomena are predicted. The reliability of Stern-Gerlach experiments to measure spin projections is assessed in this framework.

quant-ph↗

arXiv2002

Stern-Gerlach Entanglement in Spinor Bose-Einstein Condensates

Entanglement of spin and position variables produced by spatially inhomogeneous magnetic fields of Stern-Gerlach type acting on spinor Bose-Einstein condensates may lead to interference effects at the level of one-boson densities. A model is worked out for these effects which is amenable to analytical calculation for gaussian shaped condensates. The resulting interference effects are sensitive to the spin polarization properties of the condensate.

cond-mat↗

arXiv2000

Semiclassical description of Stern-Gerlach experiments

The motion of neutral particles with magnetic moments in an inhomogeneous magnetic field is described in a semi-classical framework. The concept of Coherent Internal States is used in the formulation of the semiclassical approximation from the full quantum mechanical expression. The classical trajectories are defined only for certain spin state, that satusfy the conditions for being Coherent Internal State. The raalibility of Stern-Gerlach experiments to measure spin projectons is assessed in this framework.

quant-ph↗

arXiv1998

Isospin structure of one- and two-phonon GDR excitations

Isospin is included in the description of Coulomb excitation of multiple giant isovector dipole resonances. In the excitation of even-even nuclei, a relevant portion of the excitation strength is shown to be associated with 1+ two-phonon states, which tends to be hindered or completely supressed in calculations in which the isospin degree of freedom is not considered. We find that the excitation cross sections is strongly dependent on the ground state isospin.

nucl-th↗

arXiv1998

Multiphonon and ``hot''-phonon Isovector Electric-Dipole Excitations

We argue that a substantial increase in the cross section for Coulomb excitation in the region of the Double Giant Dipole Resonance should be expected from Coulomb excitation of excited states involved in the spreading of the one-phonon resonance, in a manifestation of the Brink-Axel phenomenon. This generates an additional fluctuating amplitude and a corresponding new term to be added incoherently to the usual cross-section. The appropriate extension of an applicable reaction calculation is considered in order to estimate this effect.

nucl-th↗

arXiv1993

Mean Field Approximation to two-subsystems: Examples

Using the Funtional Integrals Formulation is developes a self-consistent mean field expansion to evolution operators of a system composed by two subsystems. This is a general expansion and can be generalized for more of two subsystems, which can be as system composed by fermions and bosons with an interaction between their ($σ$-model , $σ-ω$ model or maser model) as a fermionic system with two or more different interactions between fermions particles, (NJL model ).

nucl-th↗