1,018 research outputs found
Application of the -Hyperspherical Harmonics to the Study of the Continuum Limits of One-Dimensional -Models and to the Generation of High-Temperature Expansions in Higher Dimensions
In this talk we present the exact solution of the most general
one-dimensional -invariant spin model taking values in the sphere
, with nearest-neighbour interactions, and we discuss the possible
continuum limits. All these results are obtained using a high-temperature
expansion in terms of hyperspherical harmonics. Applications in higher
dimensions of the same technique are then discussed.Comment: 59208 bytes uuencoded gzip'ed (expands to 135067 bytes Postscript); 4
pages including all figures; contribution to Lattice '9
Structure of Light Scalar Mesons from D_s and D^0 Non-Leptonic Decays
Non-leptonic D meson decays may provide a reliable testbed for the multiquark
interpretation of light scalar mesons. In this letter we consider D_s decay and
show that a 4-quark f_0(980) meson could induce a decay pattern, which is
forbidden for a q-qbar constituent structure. Experimental tests to probe such
possibilities are within reach in the near future.Comment: 11 pages, 3 figures, minor changes. To appear in Phys. Lett.
Canine Antibody Response To Lutzomyia Longipalpis Saliva In Endemic Area Of Visceral Leishmaniasis
Introduction: Canine exposure to Lutzomyia longipalpis bites and the potential of Leishmania infantum transmissibility for the vector were evaluated. Methods: Immunoglobulin G (IgG) anti-Lu longipalpis saliva and -L. infantum, and blood parasite load were determined in dogs from endemic areas of visceral leishmaniasis. Results: Blood parasitism was similar between symptomatic and asymptomatic dogs. IgG anti-L. infantum was higher in symptomatic dogs, but IgG anti-Lu. longipalpis saliva was mostly observed in higher titers in asymptomatic dogs, indicating vector preference for feeding on asymptomatic dogs. Conclusions: Our data suggest a pivotal role of asymptomatic dogs in L. infantum transmission in endemic areas. © 2016, Sociedade Brasileira de Medicina Tropical. All rights reserved.49336136
Two dimensional SU(N) x SU(N) chiral models on the lattice
Lattice chiral models are analyzed by strong and weak
coupling expansions and by numerical simulations. order strong
coupling series for the free and internal energy are obtained for all . Three loop contributions to the internal energy and to the lattice
-function are evaluated for all and non-universal corrections to the
asymptotic parameter are computed in the ``temperature'' and the
``energy'' scheme. Numerical simulations confirm a faster approach to
asymptopia of the energy scheme. A phenomenological correlation between the
peak in the specific heat and the dip of the -function is observed.
Tests of scaling are performed for various physical quantities, finding
substantial scaling at . In particular, at three different
mass ratios are determined numerically and found in agreement, within
statistical errors of about 1\%, with the theoretical predictions from the
exact S-matrix theory.Comment: pre-print IFUP 29/93, revised version, 12 pages, 10 figures avaliable
on request by FAX or by mail. REVTE
Moments of the Virtual Photon Structure Function
The photon structure function is a useful testing ground for QCD. It is
perturbatively computable apart from a contribution from what is usually called
the hadronic component of the photon. There have been many proposals for this
nonperturbative part of the real photon structure function. By studying moments
of the virtual photon structure function, we explore the extent to which these
proposed nonperturbative contributions can be identified experimentally.Comment: LaTeX, 16 pages + 14 compressed and uuencoded postscript figures,
UMN-TH-1111/9
Spectrum of confining strings in SU(N) gauge theories
We study the spectrum of the confining strings in four-dimensional SU(N)
gauge theories. We compute, for the SU(4) and SU(6) gauge theories formulated
on a lattice, the string tensions sigma_k related to sources with Z_N charge k,
using Monte Carlo simulations. Our results are consistent with the sine formula
sigma_k/sigma = sin k pi/N / sin pi/N for the ratio between sigma_k and the
standard string tension sigma.
For the SU(4) and SU(6) cases the accuracy is approximately 1% and 2%,
respectively. The sine formula is known to emerge in various realizations of
supersymmetric SU(N) gauge theories. On the other hand, our results show
deviations from Casimir scaling. We also discuss an analogous behavior
exhibited by two-dimensional SU(N) x SU(N) chiral models.Comment: Latex, 34 pages, 10 figures. Results of new SU(4) simulations added.
The new data are included in the analysis, leading to improved final
estimates for SU(4). Conclusions unchange
Counter-propagating entangled photons from a waveguide with periodic nonlinearity
The conditions required for spontaneous parametric down-conversion in a
waveguide with periodic nonlinearity in the presence of an unguided pump field
are established. Control of the periodic nonlinearity and the physical
properties of the waveguide permits the quasi-phase matching equations that
describe counter-propagating guided signal and idler beams to be satisfied. We
compare the tuning curves and spectral properties of such counter-propagating
beams to those for co-propagating beams under typical experimental conditions.
We find that the counter-propagating beams exhibit narrow bandwidth permitting
the generation of quantum states that possess discrete-frequency entanglement.
Such states may be useful for experiments in quantum optics and technologies
that benefit from frequency entanglement.Comment: submitted to Phys. Rev.
Progress in Lattice Field Theory Algorithms
I present a summary of recent algorithmic developments for lattice field
theories. In particular I give a pedagogical introduction to the new
Multicanonical algorithm, and discuss the relation between the Hybrid
Overrelaxation and Hybrid Monte Carlo algorithms. I also attempt to clarify the
role of the dynamical critical exponent z and its connection with
`computational cost.' [Includes four PostScript figures]Comment: 27 page
Counting valence quarks at RHIC and LHC
We consider the Nuclear Modification Ratios in heavy ion collisions, R_CP and
R_AA, in the region of intermediate transverse momentum, and study the
dependency upon the constituent quark composition of the observed hadron.
Adopting a two component recombination/fragmentation model, validated by
experimental information from STAR and PHENIX, we show that a clear distinction
is predicted for the f0(980) between the assumptions of or
diquark-antidiquark content.Comment: 14 pages, 11 eps figures, added figures and minor corrections, to
appear in Phys. Lett.
Inorganic mercury modifies Ca2+ signals, triggers apoptosis and potentiates NMDA toxicity in cerebellar granule neurons
Hg2+ (0.1 microM-0.5 microM) modified the Ca2+ signals elicited by either KCl or the glutamate-receptor agonist, N-methyl-D-aspartate (NMDA), in cerebellar granule cells (CGCs). Hg2+ enhanced the intracellular Ca2+ transient elicited by high K+ and prevented a complete recovery of the resting intracellular Ca2+ concentration ([Ca2+]i) after either KCl or NMDA stimulation. Higher Hg2+ concentrations (up to 1 microM) increased [Ca2+]i directly. Following the short-term exposure to Hg2+, CGCs underwent apoptosis, which was identified by the cleavage of DNA into large (700-50 kbp) and oligonucleosomal DNA fragments, and by the appearance of typical apoptotic nuclei. Combined treatment with 0.1-0.3 microM Hg2+ and a sublethal NMDA concentration (50 microM) potentiated DNA fragmentation and apoptotic cell death. When the exposure to Hg2+ was carried out in Ca2+-free media or in the presence of Ca2+ channel blockers (L-type or NMDA-R antagonists), the effects on signalling and apoptosis were prevented. Our results suggest that very low Hg2+ concentrations can trigger apoptosis in CGCs by facilitating Ca2+ entry through membrane channels
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