7 research outputs found
Shell-model phenomenology of low-momentum interactions
The first detailed comparison of the low-momentum interaction V_{low k} with
G matrices is presented. We use overlaps to measure quantitatively the
similarity of shell-model matrix elements for different cutoffs and oscillator
frequencies. Over a wide range, all sets of V_{low k} matrix elements can be
approximately obtained from a universal set by a simple scaling. In an
oscillator mean-field approach, V_{low k} reproduces satisfactorily many
features of the single-particle and single-hole spectra on closed-shell nuclei,
in particular through remarkably good splittings between spin-orbit partners on
top of harmonic oscillator closures. The main deficiencies of pure two-nucleon
interactions are associated with binding energies and with the failure to
ensure magicity for the extruder-intruder closures. Here, calculations
including three-nucleon interactions are most needed. V_{low k} makes it
possible to define directly a meaningful unperturbed monopole Hamiltonian, for
which the inclusion of three-nucleon forces is tractable.Comment: 5 pages, 4 figures, minor additions, to appear as Rapid Comm. in
Phys. Rev.
The anatomy of the simplest Duflo-Zuker mass formula
The simplest version of the Duflo-Zuker mass model (due entirely to the late
Jean Duflo) is described by following step by step the published computer code.
The model contains six macroscopic monopole terms leading asymptotically to a
Liquid Drop form, three microscopic terms supposed to mock configuration mixing
(multipole) corrections to the monopole shell effects, and one term in charge
of detecting deformed nuclei and calculating their masses. A careful analysis
of the model suggests a program of future developments that includes a
complementary approach to masses based on an independently determined monopole
Hamiltonian, a better description of deformations and specific suggestions for
the treatment of three body forces.Comment: 30 pages, 21 figures, extensives changes to improve presentation and
clarity, with an ample discussion of the anomalous term. Accepted for
publication in Nuclear Physics
Ground state energy fluctuations in the Nuclear Shell Model
Statistical fluctuations of the nuclear ground state energies are estimated
using shell model calculations in which particles in the valence shells
interact through well defined forces, and are coupled to an upper shell
governed by random 2-body interactions. Induced ground-state energy
fluctuations are found to be one order of magnitude smaller than those
previously associated with chaotic components, in close agreement with
independent perturbative estimates based on the spreading widths of excited
states.Comment: 4 pages, 4 figures, to be published in Physics Leters
Balanced gene losses, duplications and intensive rearrangements led to an unusual regularly sized genome in Arbutus unedo chloroplasts
Completely sequenced plastomes provide a valuable source of information about the duplication, loss, and transfer events of chloroplast genes and phylogenetic data for resolving relationships among major groups of plants. Moreover, they can also be useful for exploiting chloroplast genetic engineering technology. Ericales account for approximately six per cent of eudicot diversity with 11,545 species from which only three complete plastome sequences are currently available. With the aim of increasing the number of ericalean complete plastome sequences, and to open new perspectives in understanding Mediterranean plant adaptations, a genomic study on the basis of the complete chloroplast genome sequencing of Arbutus unedo and an updated phylogenomic analysis of Asteridae was implemented. The chloroplast genome of A. unedo shows extensive rearrangements but a medium size (150,897 nt) in comparison to most of angiosperms. A number of remarkable distinct features characterize the plastome of A. unedo: five-fold dismissing of the SSC region in relation to most angiosperms; complete loss or pseudogenization of a number of essential genes; duplication of the ndhH-D operon and its location within the two IRs; presence of large tandem repeats located near highly re-arranged regions and pseudogenes. All these features outline the primary evolutionary split between Ericaceae and other ericalean families. The newly sequenced plastome of A. unedo with the available asterid sequences allowed the resolution of some uncertainties in previous phylogenies of Asteridae