2,991 research outputs found
Effect of residual many-body forces due to the evolution in the in-medium similarity renormalization group method
In the past few years in-medium similarity renormalization group methods have
been introduced and developed. In these methods the Hamiltonian is evolved
using a unitary transformation in order to decouple a reference state from the
rest of the Hilbert space. The evolution by itself will generate, even if we
start from a two-body interaction, many-body forces which are usually
neglected. In this work we estimate the effect of these residual many-body
forces by comparing results obtained with the Hybrid Multi-determinant method,
which keeps the Hamiltonian within the two-body sector, with the corresponding
ones obtained with the in-medium similarity renormalization group. Although
percentage-wise the effect of neglecting these induced many-body forces is not
too large, they can be appreciable depending on the nucleus, the shell model
space and the harmonic oscillator frequency.Comment: accepted version J. of Phys.
A Time Dependent Multi-Determinant approach to nuclear dynamics
We study a multi-determinant approach to the time evolution of the nuclear
wave functions (TDMD). We employ the Dirac variational principle and use as
anzatz for the nuclear wave-function a linear combination of Slater
determinants and derive the equations of motion. We demonstrate explicitly that
the norm of the wave function and the energy are conserved during the time
evolution. This approach is a direct generalization of the time dependent
Hartree-Fock method. We apply this approach to a case study of using
the N3LO interaction renormalized to 4 major harmonic oscillator shells. We
solve the TDMD equations of motion using Krylov subspace methods of Lanczos
type. We discuss as an application the isoscalar monopole strength function.Comment: 38 pages, additional calculations included. Accepted for publication,
Int. J. of Mod. Phys.
Ab-initio calculation of the binding energy with the Hybrid Multideterminant scheme
We perform an ab-initio calculation for the binding energy of using
the CD-Bonn 2000 NN potential renormalized with the Lee-Suzuki method. The
many-body approach to the problem is the Hybrid Multideterminant method. The
results indicate a binding energy of about , within a few hundreds KeV
uncertainty. The center of mass diagnostics are also discussed.Comment: 18 pages with 3 figures. More calculations added, to be published in
EPJ
Intensity correlations, entanglement properties and ghost imaging in multimode thermal-seeded parametric downconversion: Theory
We address parametric-downconversion seeded by multimode pseudo-thermal
fields. We show that this process may be used to generate multimode pairwise
correlated states with entanglement properties that can be tuned by controlling
the seed intensities. Multimode pseudo-thermal fields seeded
parametric-downconversion represents a novel source of correlated states, which
allows one to explore the classical-quantum transition in pairwise correlations
and to realize ghost imaging and ghost diffraction in regimes not yet explored
by experiments.Comment: 9 pages, 3 figure
The Luminosity Function of 81 Abell Clusters from the CRoNaRio catalogues
We present the composite luminosity function (hereafter LF) of galaxies for
81 Abell clusters studied in our survey of the Northern Hemisphere, using DPOSS
data processed by the CRoNaRio collaboration. The derived LF is very accurate
due to the use of homogeneous data both for the clusters and the control fields
and to the local estimate of the background, which takes into account the
presence of large-scale structures and of foreground clusters and groups. The
global composite LF is quite flat down to has a slope
with minor variations from blue to red filters, and
mag ( km s Mpc) in the
and filters, respectively (errors are detailed in the text). We find a
significant difference between rich and poor clusters thus arguing in favour of
a dependence of the LF on the properties of the environment.Comment: 8 pages, 5 figures. Contribution to the IAP 2000 Conference
"Constructing the Universe with Clusters of Galaxies", Paris, July 200
Morphology of low-redshift compact galaxy clusters I. Shapes and radial profiles
The morphology of clusters of galaxies may be described with a set of
parameters which contain information about the formation and evolutionary
history of these systems. In this paper we present a preliminary study of the
morphological parameters of a sample of 28 compact Abell clusters extracted
from DPOSS data. The morphology of galaxy clusters is parameterized by their
apparent ellipticity, position angle of the major axis, centre coordinates,
core radius and beta-model power law index. Our procedure provides estimates of
these parameters by simultaneously fitting them all, overcoming some of the
difficulties induced by sparse data and low number statistics typical of this
kind of analysis. The cluster parameters were fitted in a 3 x 3 h^-2 sqMpc
region, measuring the background in a 2 <R< 2.5 h^-1Mpc annulus. We also
explore the correlations between shape and profile parameters and other cluster
properties. One third of this compact cluster sample has core radii smaller
than 50 h^-1 kpc, i.e. near the limit that our data allow us to resolve,
possibly consistent with cusped models. The remaining clusters span a broad
range of core radii up to 750 h^-1 kpc. More than 80 per cent of this sample
has ellipticity higher than 0.2. The alignment between the cluster and the
major axis of the dominant galaxy is confirmed, while no correlation is
observed with other bright cluster members. No significant correlation is found
between cluster richness and ellipticity. Instead, cluster richness is found to
correlate, albeit with large scatter, with the cluster core radius.[abridged]Comment: 23 pages, 17 figures, accepted for publication in MNRAS. Full paper
including full resolution figures 2 and 9 at
http://www.eso.org/~vstrazzu/P/ME1030fv.pd
An efficient method to evaluate energy variances for extrapolation methods
The energy variance extrapolation method consists in relating the approximate
energies in many-body calculations to the corresponding energy variances and
inferring eigenvalues by extrapolating to zero variance. The method needs a
fast evaluation of the energy variances. For many-body methods that expand the
nuclear wave functions in terms of deformed Slater determinants, the best
available method for the evaluation of energy variances scales with the sixth
power of the number of single-particle states. We propose a new method which
depends on the number of single-particle orbits and the number of particles
rather than the number of single-particle states. We discuss as an example the
case of using the chiral N3LO interaction in a basis consisting up to
184 single-particle states.Comment: 16 pages, 2 figure
An automatic procedure to extract galaxy clusters from CRoNaRio catalogs
We present preliminary results of a simple peak finding algorithm applied to
catalogues of galaxies, extracted from the Second Palomar Sky Survey in the
framework of the CRoNaRio project. All previously known Abell and Zwicky
clusters in a test region of 5x5 sq. deg. are recovered and new candidate
clusters are also detected. This algorithm represents an alternative way of
searching for galaxy clusters with respect to that implemented and tested at
Caltech on the same type of data (Gal et al. 1998).Comment: in the proceeding of the XLIII SAIt national conference Mem. Soc.
Astr. It., in pres
The Determination of Nuclear Level Densities from Experimental Information -
A novel Information Theory based method for determining the density of states
from prior information is presented. The energy dependence of the density of
states is determined from the observed number of states per energy interval and
model calculations suggest that the method is sufficiently reliable to
calculate the thermal properties of nuclei over a reasonable temperature range.Comment: 7 pages + 6 eps figures, REVTEX 3.
Recommended from our members
Optimization of blade profiles for the Wells turbine
A Wells turbine, when coupled with an oscillating water column, allows the generation of power from the energy in waves on the surface of the ocean. In the present work, a tabu search is used to control the process of optimising the blade profile in the Wells turbine for greater performance, by maximising the torque coefficient. A free form deformation method is used as an efficient means of manipulating the blade profile and computational fluid dynamics in OpenFOAM are used to assess each profile in both two and three dimensions. Investigations into both the flow coefficient at which the optimisation is performed and the number of control variables in the free form deformation tool are performed before optimisations are done on a two-dimensional blade at the hub and tip solidities. This results in increases to the torque coefficient of 34% and 32% at the tip and hub solidities, respectively. These results are then applied to the three-dimensional turbine, giving a 14% increase in the torque coefficient. The results are assessed and an improved method of optimising the blade in two dimensions is proposed.Regione Autonoma Sardegna (grant funding co-authors from University of Cagliari
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