RT Journal Article
T1 Phase diagram of an extended Agassi model
A1 García Ramos, José Enrique
A1 Dukelsky, J.
A1 Pérez Fernández, Pedro
A1 Arias Carrasco, José Miguel
AB Background: The Agassi model [D. Agassi, Nucl. Phys. A 116, 49 (1968)] is an extension of the Lipkin-Meshkov-Glick (LMG) model [H. J. Lipkin, N. Meshkov, and A. J. Glick, Nucl. Phys. 62, 188 (1965)] that incorporates the pairing interaction. It is a schematic model that describes the interplay between particle-hole and pair correlations. It was proposed in the 1960s by D. Agassi as a model to simulate the properties of the quadrupole plus pairing model.Purpose: The aim of this work is to extend a previous study by Davis and Heiss [J. Phys. G: Nucl. Phys. 12, 805 (1986)] generalizing the Agassi model and analyze in detail the phase diagram of the model as well as the different regions with coexistence of several phases.Method: We solve the model Hamiltonian through the Hartree-Fock-Bogoliubov (HFB) approximation, introducing two variational parameters that play the role of order parameters. We also compare the HFB calculations with the exact ones.Results: We obtain the phase diagram of the model and classify the order of the different quantum phase transitions appearing in the diagram. The phase diagram presents broad regions where several phases, up to three, coexist. Moreover, there is also a line and a point where four and five phases are degenerated, respectively.Conclusions: The phase diagram of the extended Agassi model presents a rich variety of phases. Phase coexistence is present in extended areas of the parameter space. The model could be an important tool for benchmarking novel many-body approximations.
PB American Physical Society
SN 2469-9985
SN 2469-9993 (electrónico)
YR 2018
FD 2018
LK http://hdl.handle.net/10272/14736
UL http://hdl.handle.net/10272/14736
LA eng
DS Repositorio Institucional de la Universidad de Huelva
RD 30 may 2026