arXiv subjects

M. A. Caprio

Publications and source records attributed to M. A. Caprio.

46 records · Page 3Linked to original sources

arXiv2007

Excited state quantum phase transitions in many-body systems

Phenomena analogous to ground state quantum phase transitions have recently been noted to occur among states throughout the excitation spectra of certain many-body models. These excited state phase transitions are manifested as simultaneous singularities in the eigenvalue spectrum (including the gap or level density), order parameters, and wave function properties. In this article, the characteristics of excited state quantum phase transitions are investigated. The finite-size scaling behavior is determined at the mean field level. It is found that excited state quantum phase transitions are universal to two-level bosonic and fermionic models with pairing interactions.

quant-ph↗

arXiv2007

Analytic descriptions for transitional nuclei near the critical point

Exact solutions of the Bohr Hamiltonian with a five-dimensional square well potential, in isolation or coupled to a fermion by the five-dimensional spin-orbit interaction, are considered as examples of a new class of dynamical symmetry or Bose-Fermi dynamical symmetry. The solutions provide baselines for experimental studies of even-even [E(5)] and odd-mass [E(5|4)] nuclei near the critical point of the spherical to deformed gamma-unstable phase transition.

nucl-th↗

arXiv2005

Effects of beta-gamma coupling in transitional nuclei and the validity of the approximate separation of variables

Exact numerical diagonalization is carried out for the Bohr Hamiltonian with a beta-soft, axially stabilized potential. Wave function and observable properties are found to be dominated by strong beta-gamma coupling effects. The validity of the approximate separation of variables introduced with the X(5) model, extensively applied in recent analyses of axially stabilized transitional nuclei, is examined, and the reasons for its breakdown are analyzed.

nucl-th↗

arXiv2005

LevelScheme: A level scheme drawing and scientific figure preparation system for Mathematica

LevelScheme is a scientific figure preparation system for Mathematica. The main emphasis is upon the construction of level schemes, or level energy diagrams, as used in nuclear, atomic, molecular, and hadronic physics. LevelScheme also provides a general infrastructure for the preparation of publication-quality figures, including support for multipanel and inset plotting, customizable tick mark generation, and various drawing and labeling tasks. Coupled with Mathematica's plotting functions and powerful programming language, LevelScheme provides a flexible system for the creation of figures combining diagrams, mathematical plots, and data plots.

physics.comp-ph↗

arXiv2005

Phase structure of a two-fluid bosonic system

The phase diagram of a two-fluid bosonic system is investigated. The proton-neutron interacting boson model (IBM-2) possesses a rich phase structure involving three control parameters and multiple order parameters. The surfaces of quantum phase transition between spherical, axially-symmetric deformed, and SU*(3) triaxial phases are determined, and the evolution of classical equilibrium properties across these transitions is investigated. Spectroscopic observables are considered in relation to the phase diagram.

nucl-th↗

arXiv2005

Application of the coherent state formalism to multiply excited states

A general expression is obtained for the matrix element of an m-body operator between coherent states constructed from multiple orthogonal coherent boson species. This allows the coherent state formalism to be applied to states possessing an arbitrarily large number of intrinsic excitation quanta. For illustration, the formalism is applied to the two-dimensional vibron model [U(3) model], to calculate the energies of all excited states in the large-N limit.

math-ph↗

arXiv2005

Triaxiality, chirality and gamma-softness

Current work explores the impact of gamma-softness on partner bands built on the h11/2h11/2 proton-particle-neutron-hole configurations in triaxial odd-odd nuclei. The results of calculations conducted using a core-particle-hole coupling are presented. The model Hamiltonian includes the collective core, the single-particle valence nucleons, and separable quadrupole-quadrupole interactions. The Kerman-Klein method was applied to find eigenstates, which provided a convenient way for exploring core effects. Calculations were made for triaxial cores with various gamma-softness using the General Collective Model keeping the expectation value for the triaxiality parameter fixed at =30 deg. The degeneracy in the proton-neutron h11/2h11/2 bands results from the calculations for the gamma-rigid core but is lifted for the gamma-unstable core.

nucl-th↗

arXiv2004

Phase structure of the two-fluid proton-neutron system

The phase structure of a two-fluid bosonic system is investigated. The proton-neutron interacting boson model (IBM-2) posesses a rich phase structure involving three control parameters and multiple order parameters. The surfaces of quantum phase transition between spherical, axially-symmetric deformed, and SU*(3) triaxial phases are determined.

nucl-th↗

arXiv2004

Consequences of wall stiffness for a beta-soft potential

Modifications of the infinite square well E(5) and X(5) descriptions of transitional nuclear structure are considered. The eigenproblem for a potential with linear sloped walls is solved. The consequences of the introduction of sloped walls and of a quadratic transition operator are investigated.

nucl-th↗

arXiv2003

Simplified approach to the application of the geometric collective model

The predictions of the geometric collective model (GCM) for different sets of Hamiltonian parameter values are related by analytic scaling relations. For the quartic truncated form of the GCM -- which describes harmonic oscillator, rotor, deformed gamma-soft, and intermediate transitional structures -- these relations are applied to reduce the effective number of model parameters from four to two. Analytic estimates of the dependence of the model predictions upon these parameters are derived. Numerical predictions over the entire parameter space are compactly summarized in two-dimensional contour plots. The results considerably simplify the application of the GCM, allowing the parameters relevant to a given nucleus to be deduced essentially by inspection. A precomputed mesh of calculations covering this parameter space and an associated computer code for extracting observable values are made available through the Electronic Physics Auxiliary Publication Service. For illustration, the nucleus 102Pd is considered.

nucl-th↗