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.Comment: RevTeX 4, 4 pages, as published in Phys. Rev. Let

Generalized seniority for the shell model with realistic interactions

The generalized seniority scheme has long been proposed as a means of dramatically reducing the dimensionality of nuclear shell model calculations, when strong pairing correlations are present. However, systematic benchmark calculations, comparing results obtained in a model space truncated according to generalized seniority with those obtained in the full shell model space, are required to assess the viability of this scheme. Here, a detailed comparison is carried out, for semimagic nuclei taken in a full major shell and with realistic interactions. The even-mass and odd-mass Ca isotopes are treated in the generalized seniority scheme, for generalized seniority v<=3. Results for level energies, orbital occupations, and electromagnetic observables are compared with those obtained in the full shell model space.Comment: 13 pages, 8 figures; published in Phys. Rev.

STAGGERED CATAMARANS: EXPERIMENTAL DATA AND FEASIBILITY STUDY FOR ENVIRONMENT FRIENDLY SERVICE

In the last years, displacement hulls for intermediate Froude numbers (Fn<0.6) have been studied at the Dipartimento di Ingegneria Navale of the Università degli Studi di Napoli FEDERICO II (DIN). Amongst the solutions tested, asymmetric multihulls seem to be quite interesting. Particularly, the scarce amount of experimental data available for staggered catamarans led to a research program in the towing tank, to evaluate the relation between total resistance of ship, stagger of demihulls and displacement. In this paper we will present the experimental data obtained in the first step of the carried out research. Particularly, hull performances evaluated for three Length to Displacement Ratios (L/1/3 = 4.62, 5.08, 5.76) and four staggers (6, 10, 20, 30 % of LWL) are shown for Fn < 0.5. The obtained results highlighted the suitability of the studied solutions for inland waterways and especially for urban services, where low environmental impact (wave wash and atmospheric pollution) is growing in social interest. The feasibility of the tested solutions was evaluated through a case study about passenger ferries in urban service. In the paper, general arrangements and cost considerations are presented

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.Comment: LaTeX (iopart); 10 pages; to be published in J. Phys.

Exact diagonalization of the Bohr Hamiltonian for rotational nuclei: Dynamical gamma softness and triaxiality

Detailed quantitative predictions are obtained for phonon and multiphonon excitations in well-deformed rotor nuclei within the geometric framework, by exact numerical diagonalization of the Bohr Hamiltonian in an SO(5) basis. Dynamical gamma deformation is found to significantly influence the predictions through its coupling to the rotational motion. Basic signatures for the onset of rigid triaxial deformation are also obtained.Comment: 17 pages, 10 figures; to be published Phys. Rev.

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.Comment: LaTeX (elsart), 53 pages; typographical correction to (3.15