5,473 research outputs found
Hybrid Multideterminant calculation of energy levels of carbon isotopes with a chiral effective nucleon-nucleon interaction
We perform calculations for the binding energies and low-lying levels of
nuclei starting from the chiral
nucleon-nucleon potential within the framework of the Hybrid
Multideterminant scheme. The calculations are restricted to 4 major harmonic
oscillator shells, via the Lee-Suzuki renormalization scheme. The results are
compared with the experimental data.Comment: 24 pages 6 figure
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.
Many-body calculations with Deuteron based single-particle bases and their associated natural orbits
We use the recently introduced single-particle states obtained from localized
Deuteron wave-functions as a basis for nuclear many-body calculations. We show
that energies can be substantially lowered if the natural orbits obtained from
this basis are used. We use this modified basis for , and
employing the bare Nucleon-Nucleon interaction. The
lowering of the energies increases with the mass. Although in principle natural
orbits require a full scale preliminary many-body calculation, we found that an
approximate preliminary many-body calculation, with a marginal increase in the
computational cost, is sufficient. The use of natural orbits based on an
harmonic oscillator basis leads to a much smaller lowering of the energies for
a comparable computational cost.Comment: Accepted Physica Script
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
SPA+RPA approach to canonical and grandcanonical treatments of nuclear level densities
Using an exactly solvable pairing model Hamiltonian in the static path
approximation together with small-amplitude quantal fluctuation corrections in
random phase approximation (SPA+RPA), we have analyzed the behaviour of
canonical (number projected) and grandcanonical treatments of nuclear level
densities as a function of temperature and number of particles. For small
particle numbers at a low temperature, we find that though the grandcanonical
partition function in SPA+RPA approach is quite close to its exact value, the
small errors in its estimation causes significant suppression of level density
obtained using number projected partition function. The results are also
compared with the smoothed out exact values of level density. Within this model
study, it appears that due to saddle point approximation to multiple
Laplace-back transform, the grandcanonical treatment of level density at low
temperature may be reliable only for relatively large number of particles.Comment: 11 pages(LaTex), figure available by the author, accepted for
publication in Physics Letters
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