2 research outputs found
Quantum phase transitions in the interacting boson model
This review is focused on various properties of quantum phase transitions
(QPTs) in the Interacting Boson Model (IBM) of nuclear structure. The model in
its infinite-size limit exhibits shape-phase transitions between spherical,
deformed prolate, and deformed oblate forms of the ground state. Finite-size
precursors of such behavior are verified by robust variations of nuclear
properties (nuclear masses, excitation energies, transition probabilities for
low lying levels) across the chart of nuclides. Simultaneously, the model
serves as a theoretical laboratory for studying diverse general features of
QPTs in interacting many-body systems, which differ in many respects from
lattice models of solid-state physics. We outline the most important fields of
the present interest: (a) The coexistence of first- and second-order phase
transitions supports studies related to the microscopic origin of the QPT
phenomena. (b) The competing quantum phases are characterized by specific
dynamical symmetries and novel symmetry related approaches are developed to
describe also the transitional dynamical domains. (c) In some parameter
regions, the QPT-like behavior can be ascribed also to individual excited
states, which is linked to the thermodynamic and classical descriptions of the
system. (d) The model and its phase structure can be extended in many
directions: by separating proton and neutron excitations, considering
odd-fermion degrees of freedom or different particle-hole configurations, by
including other types of bosons, higher order interactions, and by imposing
external rotation. All these aspects of IBM phase transitions are relevant in
the interpretation of experimental data and important for a fundamental
understanding of the QPT phenomenon.Comment: a review article, 71 pages, 18 figure