22,869 research outputs found
Measurement of anisotropies in the large-scale diffuse gamma-ray emission
We have performed the first measurement of the angular power spectrum in the
large-scale diffuse emission at energies from 1-50 GeV. We compared results
from data and a simulated model in order to identify significant differences in
anisotropy properties. We found angular power above the photon noise level in
the data at multipoles greater than ~ 100 for energies 1< E <10 GeV. The excess
power in the data suggests a contribution from a point source population not
present in the model.Comment: Contribution to SciNeGHE 2010, Trieste, Italy, September 2010; 4
pages, 5 figure
Optimum matchings in weighted bipartite graphs
Given an integer weighted bipartite graph we consider the problems of finding all the edges that occur in
some minimum weight matching of maximum cardinality and enumerating all the
minimum weight perfect matchings. Moreover, we construct a subgraph of
which depends on an -optimal solution of the dual linear program
associated to the assignment problem on that allows us to reduced
this problems to their unweighed variants on . For instance, when
has a perfect matching and we have an -optimal solution of the dual
linear program associated to the assignment problem on , we solve the
problem of finding all the edges that occur in some minimum weight perfect
matching in linear time on the number of edges. Therefore, starting from
scratch we get an algorithm that solves this problem in time
, where , , and .Comment: 11 page
Microscopic study of neutron-rich Dysprosium isotopes
Microscopic studies in heavy nuclei are very scarce due to large valence
spaces involved. This computational problem can be avoided by means of the use
of symmetry based models. Ground-state, gamma and beta-bands, and their B(E2)
transition strengths in 160-168Dy isotopes, are studied in the framework of the
pseudo-SU(3) model which includes the preserving symmetry Q.Q term and the
symmetry-breaking Nilsson and pairing terms, systematically parametrized.
Additionally, three rotor-like terms are considered whose free parameters,
fixed for all members of the chain are used to fine tune the moment of inertia
of rotational bands and the band-head of gamma and beta-bands. The model
succesfully describes in a systematic way rotational features in these nuclei
and allows to extrapolate toward the midshell nucleus 170Dy. The results
presented show that it is possible to study full chain of isotopes or isotones
in the region with the present model
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
Non-Hermitian robust edge states in one-dimension: Anomalous localization and eigenspace condensation at exceptional points
Capital to topological insulators, the bulk-boundary correspondence ties a
topological invariant computed from the bulk (extended) states with those at
the boundary, which are hence robust to disorder. Here we put forward an
ordering unique to non-Hermitian lattices, whereby a pristine system becomes
devoid of extended states, a property which turns out to be robust to disorder.
This is enabled by a peculiar type of non-Hermitian degeneracy where a
macroscopic fraction of the states coalesce at a single point with geometrical
multiplicity of , that we call a phenomenal point.Comment: 6 pages, 4 figure
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