14,282 research outputs found
Occupation numbers in Self Consistent RPA
A method is proposed which allows to calculate within the SCRPA theory the
occupation numbers via the single particle Green function. This scheme complies
with the Hugenholtz van Hove theorem. In an application to the Lipkin model it
is found that this prescription gives consistently better results than two
other commonly used approximations: lowest order boson expansion and the number
operator method.Comment: 25 pages, 10 figures, submitted to Nucl. Phys.
Excited bands in odd-mass rare-earth nuclei
Normal parity bands are studied in 157Gd, 163Dy and 169Tm using the pseudo
SU(3) shell model. Energies and B(E2) transition strengths of states belonging
to six low-lying rotational bands with the same parity in each nuclei are
presented. The pseudo SU(3) basis includes states with pseudo-spin 0 and 1, and
1/2 and 3/2, for even and odd number of nucleons, respectively. States with
pseudo-spin 1 and 3/2 must be included for a proper description of some excited
bands.Comment: 8 pages, 6 figures, Submitted to Phys. Rev.
Microscopic description of the scissors mode in odd-mass heavy deformed nuclei
Pseudo-SU(3) shell-model results are reported for M1 excitation strengths in
157-Gd, 163-Dy and 169-Tm in the energy range between 2 and 4 MeV. Non-zero
pseudo-spin couplings between the configurations play a very important role in
determining the M1 strength distribution, especially its rapidly changing
fragmentation pattern which differs significantly from what has been found in
neighboring even-even systems. The results suggest one should examine
contributions from intruder levels.Comment: 5 pages, 3 figure
Microscopic mass estimations
The quest to build a mass formula which have in it the most relevant
microscopic contributions is analyzed. Inspired in the successful Duflo-Zuker
mass description, the challenges to describe the shell closures in a more
transparent but equally powerful formalism are discussed.Comment: 14 pages, 6 figures, submitted to Journal of Physics G, Focus issue
on Open Problems in Nuclear Structure Theor
k-Color Multi-Robot Motion Planning
We present a simple and natural extension of the multi-robot motion planning
problem where the robots are partitioned into groups (colors), such that in
each group the robots are interchangeable. Every robot is no longer required to
move to a specific target, but rather to some target placement that is assigned
to its group. We call this problem k-color multi-robot motion planning and
provide a sampling-based algorithm specifically designed for solving it. At the
heart of the algorithm is a novel technique where the k-color problem is
reduced to several discrete multi-robot motion planning problems. These
reductions amplify basic samples into massive collections of free placements
and paths for the robots. We demonstrate the performance of the algorithm by an
implementation for the case of disc robots and polygonal robots translating in
the plane. We show that the algorithm successfully and efficiently copes with a
variety of challenging scenarios, involving many robots, while a simplified
version of this algorithm, that can be viewed as an extension of a prevalent
sampling-based algorithm for the k-color case, fails even on simple scenarios.
Interestingly, our algorithm outperforms a well established implementation of
PRM for the standard multi-robot problem, in which each robot has a distinct
color.Comment: 2
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