GARCÍA RAMOS , José Enrique

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The influence of Franco Iachello in Physics during the last 50 years and, in particular, in the use of algebraic methods applied to very different physical problems has been broad, extense and have permeated most branches of Physics, from Nuclear and Molecular to Particle and Condensed Matter physics. Apart of many other contributions, at the...

The connections between the E(5) models [the original E(5) using an infinite square well, E(5)-β4, E(5)-β6, and E(5)-β8], based on particular solutions of the geometrical Bohr Hamiltonian with γ-unstable potentials, and the interacting boson model (IBM) are explored. For that purpose, the general IBM Hamiltonian for the U(5)-O(6) transition...

The connections between the Ε(5)-models (the original Ε(5) using an infinite square well, Ε(5) - β4 Ε(5) - β6 and Ε(5) - β8), based on particular solutions of the geometrical Bohr Hamiltonian with γ -unstable potentials, and the interacting boson model (IBM) are explored. For that purpose, the general IBM Hamiltonian for the U(5) - O(6)...

Exact numerical results of the interacting boson model Hamiltonian along the integrable line from U(5) to O(6) are obtained by diagonalization within boson seniority subspaces. The matrix Hamiltonian reduces to a block tridiagonal form that can be diagonalized for large number of bosons. We present results for the low-energy spectrum and the...

We study the quantum phase transition mechanisms that arise in the interacting boson model. We show that the second-order nature of the phase transition from U(5) to O(6) may be attributed to quantum integrability, whereas all the first-order phase transitions of the model are due to level repulsion with one singular point of level crossing. We...

We introduce the basic concepts of catastrophe theory needed to derive analytically the phase diagram of the proton–neutron interacting boson model (IBM-2). Previous studies [1–3] were based on numerical solutions. We here explain the whole IBM-2 phase diagram including the precise order of the phase transitions in terms of the cusp catastrophe .

The connections between the X(5) models [the original X(5) using an infinite square well, X(5)-β8, X(5)-β6, X(5)-β4, and X(5)-β2], based on particular solutions of the geometrical Bohr Hamiltonian with harmonic potential in the γ degree of freedom, and the interacting boson model (IBM) are explored. This work is the natural extension of the...

We study the phase diagram of the proton-neutron interacting boson model with special emphasis on the phase transitions leading to triaxial phases. The existence of a new critical point between spherical and triaxial shapes is reported.

Double−γ vibrations in deformed nuclei are analyzed in the context of the interacting boson model. A simple extension of the original version of the model towards higher-order interactions is required to explain the observed anharmonicities of nuclear vibrations. The influence of three- and four-body interactions on the moments of inertia of...

Background: Composed systems have become of great interest in the framework of ground-state quantum phase transitions (QPTs) and many of their properties have been studied in detail. However, in these systems, the study of the so-called excited-state quantum phase transitions (ESQPTs) has not received so much attention. Purpose: A quantum...

A systematic study of isotope chains in the rare-earth region is presented. For chains 60 144 2 154Nd, 62 146 2 160Sm, 64 148 2 162Gd, and 66 150 2 166 Dy, energy levels, E2 transition rates, and two-neutron separation energies are described by using the most general ~ up to two-body terms interacting boson model ~ IBM Hamiltonian. For...

We introduce a simple two-level boson model with the same energy surface as the Q-consistent interacting boson model Hamiltonian. The model can be diagonalized for large number of bosons and the results used to check analytical finite-size corrections to the energy gap and the order parameter in the critical region.

Background: The Agassi model [D. Agassi, Nucl. Phys. A 116, 49 (1968)NUPABL0375-947410.1016/0375-9474(68)90482-X] is an extension of the Lipkin-Meshkov-Glick (LMG) model [H. J. Lipkin, N. Meshkov, and A. J. Glick, Nucl. Phys. 62, 188 (1965)NUPHA70029-558210.1016/0029-5582(65)90862-X] that incorporates the pairing interaction. It is a schematic...

The Agassi model (Agassi 1968 Nucl. Phys. A 116 49) is a schematic two-level model that involves pairing and monopole-monopole interactions. It is, therefore, an extension of the well known Lipkin-Meshkov-Glick model (Lipkin et al 1965 Nucl. Phys. 62 188). In this paper we review the algebraic formulation of an extension of the Agassi model as...

An intrinsic-state formalism for the interacting boson model IBM-4 is presented. A basis of deformed bosons is introduced which allows the construction of a general trial wave function that has Wigner's spin-isospin SU(4) symmetry as a particular limit. Intrinsic-state calculations are compared with exact ones, showing good agreement.