245 research outputs found
Landau-Migdal vs. Skyrme
The magnitude and density-dependence of the non-spin dependent Landau-Migdal
parameters are derived from Skyrme energy functionals and compared with the
phenomenological ones. We perform RPA calculations with various approximations
for the Landau-Migdal particle-hole interaction and compare them with the
results obtained with the full Skyrme interaction. For the first time the next
to leading order in the Landau-Migdal approach is considered in nuclear
structure calculations.Comment: Dedicated to the memory of G.E. Brow
Large-scale nuclear structure studies
The problem of microscopic nuclear structure theory in large single particle basis
systems is reviewed. Several approaches are discussed, which attempt to approximate
the large model spaces numerically inaccessible in complete shell model expansions
of the nuclear wavefunctions. All of them use symmetry projected Hartree-Fock-
Bogoliubov quasiparticle configurations as basic building blocks of the theory. They
differ, however, in the degree of sophistication of the variational procedures which
are used to determine the corresponding mean fields as well as the configuration mixing,
up to a level, on which the construction of the configuration space itself is entirely left
to the dynamics of the considered system. The mathematical formalism underlying
these models is briefly summarised and the steps towards a numerical realisation are
discussed. In several examples the possibilities and the power of the models are
demonstrated and their limitations are shown. The models may provide a powerful
tool for the analysis of experimental data as well as for predictions in still unexplored
regions. On the other hand they may lead to a much better theoretical understanding
of effective nuclear interactions as well as the underlying fundamental forces
Spontaneous fission modes and lifetimes of super-heavy elements in the nuclear density functional theory
Lifetimes of super-heavy (SH) nuclei are primarily governed by alpha decay
and spontaneous fission (SF). Here we study the competing decay modes of
even-even SH isotopes with 108 <= Z <= 126 and 148 <= N <= 188 using the
state-of-the-art self-consistent nuclear density functional theory framework
capable of describing the competition between nuclear attraction and
electrostatic repulsion. The collective mass tensor of the fissioning
superfluid nucleus is computed by means of the cranking approximation to the
adiabatic time-dependent Hartree-Fock-Bogoliubov approach. Along the path to
fission, our calculations allow for the simultaneous breaking of axial and
space inversion symmetries; this may result in lowering SF lifetimes by more
than seven orders of magnitude in some cases. We predict two competing SF
modes: reflection-symmetric and reflection-asymmetric.The shortest-lived SH
isotopes decay by SF; they are expected to lie in a narrow corridor formed by
Hs, Fl, and Uuo that separates the regions of SH
nuclei synthesized in "cold fusion" and "hot fusion" reactions. The region of
long-lived SH nuclei is expected to be centered on Ds with a total
half-life of ?1.5 days.Comment: 6 pages, 4 figure
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
Log-periodic self-similarity: an emerging financial law?
A hypothesis that the financial log-periodicity, cascading self-similarity
through various time scales, carries signatures of a law is pursued. It is
shown that the most significant historical financial events can be classified
amazingly well using a single and unique value of the preferred scaling factor
lambda=2, which indicates that its real value should be close to this number.
This applies even to a declining decelerating log-periodic phase. Crucial in
this connection is identification of a "super-bubble" (bubble on bubble)
phenomenon. Identifying a potential "universal" preferred scaling factor, as
undertaken here, may significantly improve the predictive power of the
corresponding methodology. Several more specific related results include
evidence that: (i) the real end of the high technology bubble on the stock
market started (with a decelerating log-periodic draw down) in the begining of
September 2000; (ii) a parallel 2000-2002 decline seen in the Standard & Poor's
500 from the log-periodic perspective is already of the same significance as
the one of the early 1930s and of the late 1970s; (iii) all this points to a
much more serious global crash in around 2025, of course from a level much
higher (at least one order of magnitude) than in 2000.Comment: Talk given by S. Drozdz at International Econophysics Conference,
Bali, August 28-31, 2002; typos correcte
Neutron rich nuclei in density dependent relativistic Hartree-Fock theory with isovector mesons
Density dependent relativistic Hartree-Fock theory has been extended to
describe properties of exotic nuclei. The effects of Fock exchange terms and of
pi - and rho - meson contributions are discussed. These effects are found to be
more important for neutron rich nuclei than for nuclei near the valley of
stability.Comment: 10 pages, 5 figures, LaTeX, macro packages graphicx and time
Self-consistent calculations of the electric giant dipole resonances in light and heavy mass nuclei
While bulk properties of stable nuclei are successfully reproduced by
mean-field theories employing effective interactions, the dependence of the
centroid energy of the electric giant dipole resonance on the nucleon number A
is not. This problem is cured by considering many-particle correlations beyond
mean-field theory, which we do within the "Quasiparticle Time Blocking
Approximation". The electric giant dipole resonances in O, Ca,
and Pb are calculated using two new Skyrme interactions.Comment: 4 pages, 4 figure
Decomposing the stock market intraday dynamics
The correlation matrix formalism is used to study temporal aspects of the
stock market evolution. This formalism allows to decompose the financial
dynamics into noise as well as into some coherent repeatable intraday
structures. The present study is based on the high-frequency Deutsche
Aktienindex (DAX) data over the time period between November 1997 and September
1999, and makes use of both, the corresponding returns as well as volatility
variations. One principal conclusion is that a bulk of the stock market
dynamics is governed by the uncorrelated noise-like processes. There exists
however a small number of components of coherent short term repeatable
structures in fluctuations that may generate some memory effects seen in the
standard autocorrelation function analysis. Laws that govern fluctuations
associated with those various components are different, which indicates an
extremely complex character of the financial fluctuations.Comment: 15 pages, 13 PostScript figure
Quantifying dynamics of the financial correlations
A novel application of the correlation matrix formalism to study dynamics of
the financial evolution is presented. This formalism allows to quantify the
memory effects as well as some potential repeatable intradaily structures in
the financial time-series. The present study is based on the high-frequency
Deutsche Aktienindex (DAX) data over the time-period between November 1997 and
December 1999 and demonstrates a power of the method. In this way two
significant new aspects of the DAX evolution are identified: (i) the memory
effects turn out to be sizably shorter than what the standard autocorrelation
function analysis seems to indicate and (ii) there exist short term repeatable
structures in fluctuations that are governed by a distinct dynamics. The former
of these results may provide an argument in favour of the market efficiency
while the later one may indicate origin of the difficulty in reaching a
Gaussian limit, expected from the central limit theorem, in the distribution of
returns on longer time-horizons.Comment: 10 pages, 7 PostScript figures, talk presented by the first Author at
the NATO ARW on Econophysics, Prague, February 8-10, 2001; to be published in
proceedings (Physica A
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