19,182 research outputs found
Classical Integrable N=1 and Super Sinh-Gordon Models with Jump Defects
The structure of integrable field theories in the presence of jump defects is
discussed in terms of boundary functions under the Lagrangian formalism.
Explicit examples of bosonic and fermionic theories are considered. In
particular, the boundary functions for the N=1 and N=2 super sinh-Gordon models
are constructed and shown to generate the Backlund transformations for its
soliton solutions. As a new and interesting example, a solution with an
incoming boson and an outgoing fermion for the N=1 case is presented. The
resulting integrable models are shown to be invariant under supersymmetric
transformation.Comment: talk presented at the V International Symposium on Quantum Theory and
Symmetries, Valladolid, Spain, July 22-28,200
On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344
The main goal of this study is to carry out a spatially resolved
investigation of the warm interstellar medium (ISM) in the extremely metal-poor
Blue Compact Dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on the
analysis of the spatial distribution of chemical abundances, emission-line
ratios and kinematics of the ISM, and to the recent star-forming activity in
this galaxy. This study is based on optical integral field unit spectroscopy
data from Gemini Multi-Object Spectrograph at the Gemini North telescope and
archival Sloan Digital Sky Survey images. The data were obtained in two
different positions across the galaxy, obtaining a total 4 arcsec X 8 arcsec
field which encompasses most of its ISM. Emission-line maps and broad-band
images obtained in this study indicate that HS 2236+1344 hosts three Giant HII
regions. Our data also reveal some faint curved features in the BCD periphery
that might be due to tidal perturbations or expanding ionized-gas shells. The
ISM velocity field shows systematic gradients along the major axis of the BCD,
with its south-eastern and north-western half differing by ~80 km/s in their
recessional velocity. The Ha and Hb equivalent width distribution in the
central part of HS 2236+1344 is consistent with a very young (~3 Myr) burst.
Our surface photometry analysis indicates that the ongoing starburst provides
~50% of the total optical emission, similar to other BCDs. It also reveals an
underlying lower-surface brightness component with moderately red colors, which
suggest that the galaxy has undergone previous star formation. We derive an
integrated oxygen abundance of 12+log(O/H)=7.53\pm0.06 and a nitrogen-to-oxygen
ratio of log(N/O)=-1.57\pm0.19. Our results are consistent, within the
uncertainties, with a homogeneous distribution of oxygen and nitrogen within
the ISM of the galaxy. (abridged)Comment: 15 pages, 16 figures, accepted for publication in A&
Assessing the adequacy of the bare optical potential in near-barrier fusion calculation
We critically examine the differences among the different bare nuclear
interactions used in near-barrier heavy ion fusion analysis and
Coupled-Channels calculations, and discuss the possibility of extracting the
barrier parameters of the bare potential from above-barrier data. We show that
the choice of the bare potential may be critical for the analysis of the fusion
cross sections. We show also that the barrier parameters taken from above
barrier data may be very wrong.Comment: 8 pages, 3 tables, 8 figures. Submitted to Physical Review
Complete Fusion Enhancement and Suppression of Weakly Bound Nuclei at Near Barrier Energies
We consider the influence of breakup channels on the complete fusion of
weakly bound systems in terms of dynamic polarization potentials. It is argued
that the enhancement of the cross section at sub-barrier energies may be
consistent with recent experimental observations that nucleon transfer, often
leading to breakup, is dominant compared to direct breakup. The main trends of
the experimental complete fusion cross section for Li + Bi are
analyzed in the framework of the DPP approach.Comment: 12 pages, 2 figure
Continuum-continuum coupling and polarization potentials for weakly bound system
We investigate the influence of couplings among continuum states in
collisions of weakly bound nuclei. For this purpose, we compare cross sections
for complete fusion, breakup and elastic scattering evaluated by continuum
discretized coupled channel (CDCC) calculations, including and not including
these couplings. In our study, we discuss this influence in terms of the
polarization potentials that reproduce the elastic wave function of the coupled
coupled channel method in single channel calculations. We find that the
inclusion of couplings among the continuum states renders the real part of the
polarization potential more repulsive, whereas it leads to weaker apsorption to
the breakup channel. We show that the non-inclusion of continuum-continuum
couplings in CDCC calculations may not lead to qualitative and quantitative
wrong conclusions.Comment: 4 pages, 4 figures. Submitted to Phys. Rev.
Counting solutions from finite samplings
We formulate the solution counting problem within the framework of inverse
Ising problem and use fast belief propagation equations to estimate the entropy
whose value provides an estimate on the true one. We test this idea on both
diluted models (random 2-SAT and 3-SAT problems) and fully-connected model
(binary perceptron), and show that when the constraint density is small, this
estimate can be very close to the true value. The information stored by the
salamander retina under the natural movie stimuli can also be estimated and our
result is consistent with that obtained by Monte Carlo method. Of particular
significance is sizes of other metastable states for this real neuronal network
are predicted.Comment: 9 pages, 4 figures and 1 table, further discussions adde
Integrable Field Theories with Defects
The structure of integrable field theories in the presence of defects is
discussed in terms of boundary functions under the Lagrangian formalism.
Explicit examples of bosonic and fermionic theories are considered. In
particular, the boundary functions for the super sinh-Gordon model is
constructed and shown to generate the Backlund transformations for its soliton
solutions.Comment: talk presented at the XVth International Colloquium on Integrable
Systems and Quantum Symmetries, to appear in Czechoslovak Journal of Physics
(2006
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