386 research outputs found
Chiral Perturbation Theory, the expansion and Regge behaviour determine the structure of the lightest scalar meson
The leading behaviour of Unitarised Chiral Perturbation Theory
distinguishes the nature of the and the . At one loop order the
is a meson, while the is not. However, semi-local
duality between resonances and Regge behaviour cannot be satisfied for larger
, if such a distinction holds. While the at is inevitably
dominated by its di-pion component, Unitarised Chiral Perturbation Theory
beyond one loop order reveals that as increases above 6-8, the
has a sub-dominant fraction up at 1.2 GeV. Remarkably this ensures
semi-local duality is fulfilled for the range of , where the
unitarisation procedure adopted applies.Comment: 22 pages, 8 figures. Version to be published in Physical Review
Quema controlada en una comunidad típica del Sudoeste Bonaerense
El fuego controlado reduce significativamente la cobertura de las especies leñosas y favorece el aumento de la cobertura de las gramíneas deseables e intermedias. Una sola quema controlada no afecta la densidad de las especies leñosas ni de las gramíneas forrajeras perennes.Fil: Pelaez, Daniel V.. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Giorgetti, Hugo D.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Montenegro, Oscar A.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Elia, Omar Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Rodríguez, Gustavo D.. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Andrioli, Romina Jessica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); ArgentinaFil: Blazquez, Francisco Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida(i); Argentin
Vacuum energy in conical space with additional boundary conditions
Total vacuum energy of some quantized fields in conical space with additional
boundary conditions is calculated. These conditions are imposed on a
cylindrical surface which is coaxial with the symmetry axis of conical space.
The explicit form of the matching conditions depends on the field under
consideration. In the case of electromagnetic field, the perfectly conducting
boundary conditions or isorefractive matching conditions are imposed on the
cylindrical surface. For a massless scalar field, the semi-transparent
conditions (-potential) on the cylindrical shell are investigated. As a
result, the total Casimir energy of electromagnetic field and scalar field, per
a unit length along the symmetry axis, proves to be finite unlike the case of
an infinitely thin cosmic string. In these studies the spectral zeta functions
are widely used. It is shown briefly how to apply this technique for obtaining
the asymptotics of the relevant thermodynamical functions in the high
temperature limit.Comment: 29 pages, 2 figures, the title was changed for a more adequate one,
the abstract was rewritten, a few typos and minor grammar mistakes were
correcte
A Decadal Inversion of CO2 Using the Global Eulerian-Lagrangian Coupled Atmospheric Model (GELCA): Sensitivity to the Ground-Based Observation Network
We present an assimilation system for atmospheric carbon dioxide (CO2) using a Global Eulerian-Lagrangian Coupled Atmospheric model (GELCA), and demonstrate its capability to capture the observed atmospheric CO2 mixing ratios and to estimate CO2 fluxes. With the efficient data handling scheme in GELCA, our system assimilates non-smoothed CO2 data from observational data products such as the Observation Package (ObsPack) data products as constraints on surface fluxes. We conducted sensitivity tests to examine the impact of the site selections and the prior uncertainty settings of observation on the inversion results. For these sensitivity tests, we made five different sitedata selections from the ObsPack product. In all cases, the time series of the global net CO2 flux to the atmosphere stayed close to values calculated from the growth rate of the observed global mean atmospheric CO2 mixing ratio. At regional scales, estimated seasonal CO2 fluxes were altered, depending on the CO2 data selected for assimilation. Uncertainty reductions (URs) were determined at the regional scale and compared among cases. As measures of the model-data mismatch, we used the model-data bias, root-mean-square error, and the linear correlation. For most observation sites, the model-data mismatch was reasonably small. Regarding regional flux estimates, tropical Asia was one of the regions that showed a significant impact from the observation network settings. We found that the surface fluxes in tropical Asia were the most sensitive to the use of aircraft measurements over the Pacific, and the seasonal cycle agreed better with the results of bottom-up studies when the aircraft measurements were assimilated. These results confirm the importance of these aircraft observations, especially for constraining surface fluxes in the tropics
The preliminary lattice QCD calculation of meson decay width
We present a direct lattice QCD calculation of the meson decay width
with the s-wave scattering phase shift for the isospin pion-kaon () system. We employ a special finite size formula, which is the extension of
the Rummukainen-Gottlieb formula for the system in the moving frame, to
calculate the scattering phase, which indicates a resonance around
meson mass. Through the effective range formula, we extract the effective
coupling constant GeV and
decay width MeV. Our simulations are done with the MILC
gauge configurations with flavors of the "Asqtad" improved staggered
dynamical sea quarks on a lattice at and lattice spacing fm.Comment: To make it concise. arXiv admin note: text overlap with
arXiv:1110.1422, but much of v1 text overlap with articles by same and other
authors remove
Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere
The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy
Matching Regge Theory to the OPE
The spectra of masses and decay constants for non-strange meson resonances in
the energy range 0--2.5 GeV is analyzed. It is known from meson phenomenology
that for given quantum numbers these spectra approximately follow linear
trajectories with a universal slope. These facts can be understood in terms of
an effective string description for QCD. For light meson states the
trajectories deviate noticeably from the linear behavior. We investigate the
possible corrections to the linear trajectories by matching two-point
correlators of quark currents to the Operator Product Expansion (OPE). We find
that the allowed modifications to the linear Regge behavior must decrease
rapidly with the principal quantum number. After fitting the lightest states in
each channel and certain low-energy constants the whole spectrum for meson
masses and residues is obtained in a satisfactory agreement with phenomenology.
We briefly speculate on possible implications for the QCD effective string.Comment: 24 pages, Latex, significant changes in discussion of fits, more refs
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Unitarized Chiral Perturbation Theory in a finite volume: scalar meson sector
We develop a scheme for the extraction of the properties of the scalar mesons
f0(600), f0(980), and a0(980) from lattice QCD data. This scheme is based on a
two-channel chiral unitary approach with fully relativistic propagators in a
finite volume. In order to discuss the feasibility of finding the mass and
width of the scalar resonances, we analyze synthetic lattice data with a fixed
error assigned, and show that the framework can be indeed used for an accurate
determination of resonance pole positions in the multi-channel scattering.Comment: 15 pages, 17 figure
Chiral Symmetry and light resonances in hot and dense matter
We present a study of the scattering amplitude in the and
channels at finite temperature and nuclear density within a chiral
unitary framework. Meson resonances are dynamically generated in our approach,
which allows us to analyze the behavior of their associated scattering poles
when the system is driven towards chiral symmetry restoration. Medium effects
are incorporated in three ways: (a) by thermal corrections of the unitarized
scattering amplitudes, (b) by finite nuclear density effects associated to a
renormalization of the pion decay constant, and complementarily (c) by
extending our calculation of the scalar-isoscalar channel to account for finite
nuclear density and temperature effects in a microscopic many-body
implementation of pion dynamics. Our results are discussed in connection with
several phenomenological aspects relevant for nuclear matter and Heavy-Ion
Collision experiments, such as mass scaling vs broadening from dilepton
spectra and chiral restoration signals in the channel. We also
elaborate on the molecular nature of resonances.Comment: 14 pages, 14 figures. Contribution to Hard Probes 2008, Illa de A
Toxa, Spain, June 8th-14th 200
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