54,741 research outputs found
Exploration of The Duality Between Generalized Geometry and Extraordinary Magnetoresistance
We outline the duality between the extraordinary magnetoresistance (EMR),
observed in semiconductor-metal hybrids, and non-symmetric gravity coupled to a
diffusive gauge field. The corresponding gravity theory may be
interpreted as the generalized complex geometry of the semi-direct product of
the symmetric metric and the antisymmetric Kalb-Ramond field:
(). We construct the four dimensional covariant
field theory and compute the resulting equations of motion. The equations
encode the most general form of EMR within a well defined variational
principle, for specific lower dimensional embedded geometric scenarios. Our
formalism also reveals the emergence of additional diffusive pseudo currents
for a completely dynamic field theory of EMR. The proposed equations of motion
now include terms that induce geometrical deformations in the device geometry
in order to optimize the EMR. This bottom-up dual description between EMR and
generalized geometry/gravity lends itself to a deeper insight into the EMR
effect with the promise of potentially new physical phenomena and properties.Comment: 13 pages and 6 figures. Revised/edited for clarity and purpose.
Several references added. Updated title based on suggestions and comments
received. Version accepted for publication in Phys.Rev.
Microscopic description of fission in neutron-rich plutonium isotopes with the Gogny-D1M energy density functional
The most recent parametrization D1M of the Gogny energy density functional is
used to describe fission in the isotopes Pu. We resort to the
methodology introduced in our previous studies [Phys. Rev. C \textbf{88},
054325 (2013) and Phys. Rev. C \textbf {89}, 054310 (2014)] to compute the
fission paths, collective masses and zero point quantum corrections within the
Hartree-Fock-Bogoliubov framework. The systematics of the spontaneous fission
half-lives t, masses and charges of the fragments in Plutonium isotopes
is analyzed and compared with available experimental data. We also pay
attention to isomeric states, the deformation properties of the fragments as
well as to the competition between the spontaneous fission and -decay
modes. The impact of pairing correlations on the predicted t values is
demonstrated with the help of calculations for Pu in which the
pairing strengths of the Gogny-D1M energy density functional are modified by 5
and 10 , respectively. We further validate the use of the D1M
parametrization through the discussion of the half-lives in Fm. Our
calculations corroborate that, though the uncertainties in the absolute values
of physical observables are large, the Gogny-D1M Hartree-Fock-Bogoliubov
framework still reproduces the trends with mass and/or neutron numbers and
therefore represents a reasonable starting point to describe fission in heavy
nuclear systems from a microscopic point of view.Comment: 14 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1312.722
Properties of the predicted super-deformed band in ^{32}S
Properties like the excitation energy with respect to the ground state,
moments of inertia, B(E2) transition probabilities and stability against
quadrupole fluctuations at low spin of the predicted superdeformed band of
^{32}S are studied with the Gogny force D1S using the angular momentum
projected generator coordinate method for the axially symmetric quadrupole
moment. The Self Consistent Cranking method is also used to describe the
superdeformed rotational band. In addition, properties of some collective
normal deformed states are discussed.Comment: 7 pages, 3 figure
Microscopic description of fission in nobelium isotopes with the Gogny-D1M energy density functional
Constrained mean-field calculations, based on the Gogny-D1M energy density
functional, have been carried out to describe fission in the isotopes
No. The even-even isotopes have been considered within the standard
Hartree-Fock-Bogoliobov (HFB) framework while for the odd-mass ones the Equal
Filling Approximation (HFB-EFA) has been employed. Ground state quantum numbers
and deformations, pairing energies, one-neutron separation energies, inner and
outer barrier heights as well as fission isomer excitation energies are given.
Fission paths, collective masses and zero-point quantum vibrational and
rotational corrections are used to compute the systematic of the spontaneous
fission half-lives t both for even-even and odd-mass nuclei.
Though there exists a strong variance of the predicted fission rates with
respect to the details involved in their computation, it is shown that both the
specialization energy and the pairing quenching effects, taken into account
within the self-consistent HFB-EFA blocking procedure, lead to larger
t values in odd-mass nuclei as compared with their even-even
neighbors. Alpha decay lifetimes have also been computed using a
parametrization of the Viola-Seaborg formula. The high quality of the Gogny-D1M
functional regarding nuclear masses leads to a very good reproduction of
values and consequently of lifetimes.Comment: 13 pages, 9 figure
Microscopic description of fission in Uranium isotopes with the Gogny energy density functional
The most recent parametrizations D1S, D1N and D1M of the Gogny energy density
functional are used to describe fission in the isotopes U. Fission
paths, collective masses and zero point quantum corrections, obtained within
the constrained Hartree-Fock-Bogoliubov approximation, are used to compute the
systematics of the spontaneous fission half-lives , the masses
and charges of the fission fragments as well as their intrinsic shapes. The
Gogny-D1M parametrization has been benchmarked against available experimental
data on inner and second barrier heights, excitation energies of the fission
isomers and half-lives in a selected set of Pu, Cm, Cf, Fm, No, Rf, Sg, Hs and
Fl nuclei. It is concluded that D1M represents a reasonable starting point to
describe fission in heavy and superheavy nuclei. Special attention is also paid
to understand the uncertainties in the predicted values arising
from the different building blocks entering the standard semi-classical
Wentzel-Kramers-Brillouin formula. Although the uncertainties are large, the
trend with mass or neutron numbers are well reproduced and therefore the theory
still has predictive power. In this respect, it is also shown that
modifications of a few per cent in the pairing strength can have a significant
impact on the collective masses leading to uncertainties in the
values of several orders of magnitude.Comment: 22 pages, 17 figures; Minor modifications to previous versio
Shape evolution in Yttrium and Niobium neutron-rich isotopes
The isotopic evolution of the ground-state nuclear shapes and the systematics
of one-quasiproton configurations are studied in neutron-rich odd-A Yttrium and
Niobium isotopes. We use a selfconsistent Hartree-Fock-Bogoliubov formalism
based on the Gogny energy density functional with two parametrizations, D1S and
D1M. The equal filling approximation is used to describe odd-A nuclei
preserving both axial and time reversal symmetries. Shape-transition signatures
are identified in the N=60 isotopes in both charge radii and spin-parities of
the ground states. These signatures are a common characteristic for nuclei in
the whole mass region. The nuclear deformation and shape coexistence inherent
to this mass region are shown to play a relevant role in the understanding of
the spectroscopic features of the ground and low-lying one-quasiproton states.
Finally, a global picture of the neutron-rich A=100 mass region from Krypton up
to Molybdenum isotopes is illustrated with the systematics of the nuclear
charge radii isotopic shifts.Comment: 21 pages, 14 figures. To be published in Phys. Rev.
Shape evolution and the role of intruder configurations in Hg isotopes within the interacting boson model based on a Gogny energy density functional
The interacting boson model with configuration mixing, with parameters
derived from the self-consistent mean-field calculation employing the
microscopic Gogny energy density functional, is applied to the systematic
analysis of the low-lying structure in Hg isotopes. Excitation energies,
electromagnetic transition rates, deformation properties, and ground-state
properties of the Hg nuclei are obtained by mapping the microscopic
deformation energy surface onto the equivalent IBM Hamiltonian in the boson
condensate. These results point to the overall systematic trend of the
transition from the near spherical vibrational state in lower-mass Hg nuclei
close to Hg, onset of intruder prolate configuration as well as the
manifest prolate-oblate shape coexistence around the mid-shell nucleus
Hg, weakly oblate deformed structure beyond Hg up to the
spherical vibrational structure toward the near semi-magic nucleus Hg,
as observed experimentally. The quality of the present method in the
description of the complex shape dynamics in Hg isotopes is examined.Comment: 19 pages, 14 figures, revised version including new results and
discussions, title changed, accepted for publication in Phys. Rev.
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