635 research outputs found
Quasiparticle-vibration coupling in relativistic framework: shell structure of Z=120 isotopes
For the first time, the shell structure of open-shell nuclei is described in
a fully self-consistent extension of the covariant energy density functional
theory. The approach implies quasiparticle-vibration coupling for superfluid
systems. One-body Dyson equation formulated in the doubled quasiparticle space
of Dirac spinors is solved for nucleonic propagators in tin isotopes which
represent the reference case: the obtained energies of the single-quasiparticle
levels and their spectroscopic amplitudes are in agreement with data. The model
is applied to describe the shell evolution in a chain of superheavy isotopes
120 and finds a rather stable proton spherical shell
closure at Z = 120. An interplay of the pairing correlations and the
quasiparticle-phonon coupling gives rise for a smooth evolution of the neutron
shell gap between N = 172 and N = 184 neutron numbers. Vibrational corrections
to the alpha decay energies reach several hundred keV and can be either
positive and negative, thus also smearing the shell effects.Comment: 10 pages, 3 figure
Spectroscopy of the heaviest nuclei (theory)
Recent progress in the applications of covariant density functional theory
(CDFT) to the description of the spectroscopy of the heaviest nuclei is
reviewed. The analysis of quasiparticle spectra in actinides and the heaviest A
~ 250 nuclei provides a measure of the accuracy of the description of
single-particle energies in CDFT and an additional constraint for the choice of
effective interactions for the description of superheavy nuclei. The response
of these nuclei to the rotation is rather well described by cranked
relativistic Hartree+Bogoliubov theory and it serves as a supplementary tool in
configuration assignment in odd-mass nuclei. A systematic analysis of the
fission barriers with allowance for triaxial deformation shows that covariant
density functional theory is able to describe fission barriers on a level of
accuracy comparable with the best phenomenological macroscopic+microscopic
approaches.Comment: 10 pages, 7 figures, invited talk of A.V. Afanasjev at the
International Nuclear Physics Conference (INPC 2010), Vancouver, Canada, July
4-9, 2010, to be published in Journal of Physics G: Conference Series (JPCS
Self-consistent calculations within the Extended Theory of Finite Fermi Systems
The Extended Theory of Finite Fermi Systems(ETFFS) describes nuclear
excitations considering phonons and pairing degrees of freedom, using
experimental single particle energies and the effective Landau-Migdal
interaction. Here we use the Skyrme interactions in order to extend the range
of applicability of the ETFFS to experimentally not yet investigated
short-lived isotopes. We find that Skyrme interactions which reproduce at the
mean field level both ground state properties and nuclear excitations are able
to describe the spreading widths of the giant resonances in the new approach,
but produce shifts of the centroid energies. A renormalization of the Skyrme
interactions is required for approaches going beyond the mean field level.Comment: 7 pages, 5 figures, corrected typo
Female Scent Signals Enhances Male Resistance to Influenza
Scent of receptive females as signal to reproduction stimulate male mice to olfactory search of a potential breeding partner^1, 2^. This searching behavior is coupled with infection risk due to bacterial contamination of the fecal and urine scent marks^4^. The theoretical consideration of host evolution under inevitable parasitic pressures, including helminthes, bacteria, virus etc., predicts adaptations that help protect against parasites associated with breeding^7^. In this study, we propose that acceptation of female signals by male mice leads to adaptive redistribution of immune defense directed to protection against respiratory infection risks. Our results reveal migration of macrophages and neutrophils to upper airways upon exposure to female odor stimulus resulting in increased resistance to influenza virus in male mice. Contrary to widely accepted immunosuppressive function of female sexual signals, our data provide the first demonstration of the adaptive immunological response to female odor stimulus through induction of nonspecific immune response in upper airways
Relativistic quasiparticle time blocking approximation. II. Pygmy dipole resonance in neutron-rich nuclei
Theoretical studies of low-lying dipole strength in even-even spherical
nuclei within the relativistic quasiparticle time blocking approximation
(RQTBA) are presented. The RQTBA developed recently as an extension of the
self-consistent relativistic quasiparticle random phase approximation (RQRPA)
enables one to investigate effects of coupling of two-quasiparticle excitations
to collective vibrations within a fully consistent calculation scheme based on
covariant energy density functional theory. Dipole spectra of even-even
Sn -- Sn and Ni -- Ni isotopes calculated within
both RQRPA and RQTBA show two well separated collective structures: the
higher-lying giant dipole resonance (GDR) and the lower-lying pygmy dipole
resonance (PDR) which can be identified by a different behavior of the
transition densities of states in these regions.Comment: 28 pages, 13 figure
Microscopic description of the pygmy and giant electric dipole resonances in stable Ca isotopes
The properties of the pygmy (PDR) and giant dipole resonance (GDR)in the
stable , and isotopes have been calculated within
the \emph{Extended Theory of Finite Fermi Systems}(ETFFS). This approach is
based on the random phase approximation (RPA) and includes the single particle
continuum as well as the coupling to low-lying collectives states which are
considered in a consistent microscopic way. For we also include
pairing correlations. We obtain good agreement with the experimental data for
the gross properties of both resonances. It is demonstrated that the recently
measured A-dependence of the strength of the PDR below 10 MeV is well
understood in our model:due to the phonon coupling some of the strength in
is simply shifted beyond 10 MeV. The predicted fragmentation of the
PDR can be investigated in and experiments.
Whereas the isovector dipole strength of the PDR is small in all Ca isotopes,
we find in this region surprisingly strong isoscalar dipole states, in
agreement with an experiment. We conclude that for the
detailed understanding of the structure of excited nuclei e.g. the PDR and GDR
an approach like the present one is absolutely necessary.Comment: 6 figure
Covariant theory of particle-vibrational coupling and its effect on the single-particle spectrum
The Relativistic Mean Field (RMF) approach describing the motion of
independent particles in effective meson fields is extended by a microscopic
theory of particle vibrational coupling. It leads to an energy dependence of
the relativistic mass operator in the Dyson equation for the single-particle
propagator. This equation is solved in the shell-model of Dirac states. As a
result of the dynamics of particle-vibrational coupling we observe a noticeable
increase of the level density near the Fermi surface. The shifts of the
single-particle levels in the odd nuclei surrounding 208-Pb and the
corresponding distributions of the single-particle strength are discussed and
compared with experimental data.Comment: 27 pages, 8 figure
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