2,170 research outputs found
Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials
We analyze the spin-orbit coupling term in the nuclear energy density
functional in terms of a zero-range NN-contact interaction and finite-range
contributions from two-pion exchange. We show that the strength of the
spin-orbit contact interaction as extracted from high-precision nucleon-nucleon
potentials is in perfect agreement with that of phenomenological Skyrme forces
employed in non-relativistic nuclear structure calculations. Additional
long-range contributions from chiral two-pion exchange turn out to be
relatively small. These explicitly density-dependent contributions reduce the
ratio of the isovector to the isoscalar spin-orbit strength significantly below
the Skyrme value 1/3. We perform a similar analysis for the strength function
of the -term and find values not far from those of
phenomenological Skyrme parameterizations.Comment: 10 pages, 3 figures, accepted for publication in Physical Review C70
(2004
Levy flights and Levy -Schroedinger semigroups
We analyze two different confining mechanisms for L\'{e}vy flights in the
presence of external potentials. One of them is due to a conservative force in
the corresponding Langevin equation. Another is implemented by
Levy-Schroedinger semigroups which induce so-called topological Levy processes
(Levy flights with locally modified jump rates in the master equation). Given a
stationary probability function (pdf) associated with the Langevin-based
fractional Fokker-Planck equation, we demonstrate that generically there exists
a topological L\'{e}vy process with the very same invariant pdf and in the
reverse.Comment: To appear in Cent. Eur. J. Phys. (2010
Overlap distributions for quantum quenches in the anisotropic Heisenberg chain
The dynamics after a quantum quench is determined by the weights of the
initial state in the eigenspectrum of the final Hamiltonian, i.e., by the
distribution of overlaps in the energy spectrum. We present an analysis of such
overlap distributions for quenches of the anisotropy parameter in the
one-dimensional anisotropic spin-1/2 Heisenberg model (XXZ chain). We provide
an overview of the form of the overlap distribution for quenches from various
initial anisotropies to various final ones, using numerical exact
diagonalization. We show that if the system is prepared in the
antiferromagnetic N\'eel state (infinite anisotropy) and released into a
non-interacting setup (zero anisotropy, XX point) only a small fraction of the
final eigenstates gives contributions to the post-quench dynamics, and that
these eigenstates have identical overlap magnitudes. We derive expressions for
the overlaps, and present the selection rules that determine the final
eigenstates having nonzero overlap. We use these results to derive concise
expressions for time-dependent quantities (Loschmidt echo, longitudinal and
transverse correlators) after the quench. We use perturbative analyses to
understand the overlap distribution for quenches from infinite to small nonzero
anisotropies, and for quenches from large to zero anisotropy.Comment: 23 pages, 8 figure
Particle Dispersion on Rapidly Folding Random Hetero-Polymers
We investigate the dynamics of a particle moving randomly along a disordered
hetero-polymer subjected to rapid conformational changes which induce
superdiffusive motion in chemical coordinates. We study the antagonistic
interplay between the enhanced diffusion and the quenched disorder. The
dispersion speed exhibits universal behavior independent of the folding
statistics. On the other hand it is strongly affected by the structure of the
disordered potential. The results may serve as a reference point for a number
of translocation phenomena observed in biological cells, such as protein
dynamics on DNA strands.Comment: 4 pages, 4 figure
Effective DBHF Method for Asymmetric Nuclear Matter and Finite Nuclei
A new decomposition of the Dirac structure of nucleon self-energies in the
Dirac Brueckner-Hartree-Fock (DBHF) approach is adopted to investigate the
equation of state for asymmetric nuclear matter. The effective coupling
constants of , , and mesons with a density
dependence in the relativistic mean field approach are deduced by reproducing
the nucleon self-energy resulting from the DBHF at each density for symmetric
and asymmetric nuclear matter. With these couplings the properties of finite
nuclei are investigated. The agreement of charge radii and binding energies of
finite nuclei with the experimental data are improved simultaneously in
comparison with the projection method. It seems that the properties of finite
nuclei are sensitive to the scheme used for the DBHF self-energy extraction. We
may conclude that the properties of the asymmetric nuclear matter and finite
nuclei could be well described by the new decomposition approach of the G
matrix.Comment: 16 pages, 5 figure
In-medium chiral SU(3) dynamics and hypernuclear structure
A previously introduced relativistic energy density functional, successfully
applied to ordinary nuclei, is extended to hypernuclei. The density-dependent
mean field and the spin-orbit potential are consistently calculated for a
hyperon in the nucleus using the SU(3) extension of in-medium chiral
perturbation theory. The leading long range interaction arises from
kaon-exchange and -exchange with hyperon in the intermediate
state. Scalar and vector mean fields reflecting in-medium changes of the quark
condensates are constrained by QCD sum rules. The model, applied to oxygen as a
test case, describes spectroscopic data in good agreement with experiment. In
particular, the smallness of the spin-orbit interaction finds a
natural explanation in terms of an almost complete cancellation between
scalar-vector background contributions and long-range terms generated by
two-pion exchange.Comment: 10 pages, 2 figures, elsart class. Minor revision
Quark mean field model with density dependent couplings for finite nuclei
The quark mean field model, which describes the nucleon using the constituent
quark model, is applied to investigate the properties of finite nuclei. The
couplings of the scalar and vector mesons with quarks are made density
dependent through direct coupling to the scalar field so as to reproduce the
relativistic Brueckner-Hartree-Fock results of nuclear matter. The present
model provides satisfactory results on the properties of spherical nuclei, and
predicts an increasing size of the nucleon as well as a reduction of the
nucleon mass in the nuclear environmentComment: 8 pages, REVTeX, 8 ps figures, accepted for publication in Phys. Rev.
Neutron star properties and the equation of state of neutron-rich matter
We calculate total masses and radii of neutron stars (NS) for pure neutron
matter and nuclear matter in beta-equilibrium. We apply a relativistic nuclear
matter equation of state (EOS) derived from Dirac-Brueckner-Hartree-Fock (DBHF)
calculations. We use realistic nucleon-nucleon (NN) interactions defined in the
framework of the meson exchange potential models. Our results are compared with
other theoretical predictions and recent observational data. Suggestions for
further study are discussed.Comment: 13 pages, 9 figures, 1 table; Revised version, accepted for
publication in Physical Review
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