2,743 research outputs found
A deformed QRPA formalism for single and two-neutrino double beta decay
We use a deformed QRPA formalism to describe simultaneously the energy
distributions of the single beta Gamow-Teller strength and the two-neutrino
double beta decay matrix elements. Calculations are performed in a series of
double beta decay partners with A = 48, 76, 82, 96, 100, 116, 128, 130, 136 and
150, using deformed Woods-Saxon potentials and deformed Skyrme Hartree-Fock
mean fields. The formalism includes a quasiparticle deformed basis and residual
spin-isospin forces in the particle-hole and particle-particle channels. We
discuss the sensitivity of the parent and daughter Gamow-Teller strength
distributions in single beta decay, as well as the sensitivity of the double
beta decay matrix elements to the deformed mean field and to the residual
interactions. Nuclear deformation is found to be a mechanism of suppression of
the two-neutrino double beta decay. The double beta decay matrix elements are
found to have maximum values for about equal deformations of parent and
daughter nuclei. They decrease rapidly when differences in deformations
increase. We remark the importance of a proper simultaneous description of both
double beta decay and single Gamow-Teller strength distributions. Finally, we
conclude that for further progress in the field it would be useful to improve
and complete the experimental information on the studied Gamow-Teller strengths
and nuclear deformations.Comment: 33 pages, 19 figures. To be published in Phys. Rev.
Role of three-body interactions in formation of bulk viscosity in liquid argon
With the aim of locating the origin of discrepancy between experimental and
computer simulation results on bulk viscosity of liquid argon, a molecular
dynamic simulation of argon interacting via ab initio pair potential and
triple-dipole three-body potential has been undertaken. Bulk viscosity,
obtained using Green-Kubo formula, is different from the values obtained from
modeling argon using Lennard-Jones potential, the former being closer to the
experimental data. The conclusion is made that many-body inter-atomic
interaction plays a significant role in formation of bulk viscosity.Comment: 4 pages, 3 figure
Multi-antikaonic nuclei in the relativistic mean-field theory
Properties of multi-antikaonic nuclei (MKN), where several numbers of
mesons are bound, are studied in the relativistic mean-field model, combined
with chiral dynamics for kaonic part of the thermodynamic potential. The
density profiles for nucleons and mesons, the single particle energy of
the mesons, and binding energy of the MKN are obtained. The effects of
the interactions on these quantities are discussed in
comparison with other meson (, , and )-exchange models.
It is shown that the interactions originate from two
contributions: One is the contact interaction between antikaons inherent in
chiral symmetry, and the other is the one generated through coupling between
the and meson mean fields. Both effects of the repulsive
interactions become large on the ground state properties of the MKN as the
number of the embedded mesons increases. A relation between the
multi-antikaonic nuclei and kaon condensation in infinite and uniform matter is
mentioned.Comment: 27 pages, 13 figure
Stepwise Projection: Toward Brane Setups for Generic Orbifold Singularities
The construction of brane setups for the exceptional series E6,E7,E8 of SU(2)
orbifolds remains an ever-haunting conundrum. Motivated by techniques in some
works by Muto on non-Abelian SU(3) orbifolds, we here provide an algorithmic
outlook, a method which we call stepwise projection, that may shed some light
on this puzzle. We exemplify this method, consisting of transformation rules
for obtaining complex quivers and brane setups from more elementary ones, to
the cases of the D-series and E6 finite subgroups of SU(2). Furthermore, we
demonstrate the generality of the stepwise procedure by appealing to Frobenius'
theory of Induced Representations. Our algorithm suggests the existence of
generalisations of the orientifold plane in string theory.Comment: 22 pages, 3 figure
Shell Model Study of the Double Beta Decays of Ge, Se and Xe
The lifetimes for the double beta decays of Ge, Se and
Xe are calculated using very large shell model spaces. The two neutrino
matrix elements obtained are in good agreement with the present experimental
data. For eV we predict the following upper bounds to the
half-lives for the neutrinoless mode: , and . These results are the first from a new generation of Shell
Model calculations reaching O(10) dimensions
Nuclear deformation and neutrinoless double- decay of Zr, Mo, Ru, Pd, Te and Nd nuclei in mass mechanism
The decay of Zr, Mo,
Ru, Pd, Te and Nd isotopes for the
transition is studied in the Projected Hartree-Fock-Bogoliubov
framework. In our earlier work, the reliability of HFB intrinsic wave functions
participating in the decay of the above mentioned nuclei
has been established by obtaining an overall agreement between the
theoretically calculated spectroscopic properties, namely yrast spectra,
reduced : transition probabilities, quadrupole moments
, gyromagnetic factors as well as half-lives
for the transition and the available
experimental data. In the present work, we study the decay for the transition in the mass mechanism
and extract limits on effective mass of light as well as heavy neutrinos from
the observed half-lives using nuclear
transition matrix elements calculated with the same set of wave functions.
Further, the effect of deformation on the nuclear transition matrix elements
required to study the decay in the mass
mechanism is investigated. It is noticed that the deformation effect on nuclear
transition matrix elements is of approximately same magnitude in and decay.Comment: 15 pages, 1 figur
Significance of many-body contributions to Casimir energies
Irreducible many-body contributions to Green's functions and Casimir energies
are defined. We show that the irreducible three-body contribution to Casimir
energies are significant and can be more than twenty percent of the total
interaction energy. Irreducible three-body contribution for three parallel
semitransparent plates in the limit when two plates overlap is obtained in
terms of irreducible two-body contributions and shown to be finite and well
defined in this limit.Comment: 9 pages. Submission to proceedings of the tenth conference on quantum
field theory under the influence of external conditions (QFEXT11
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