5,328 research outputs found
The scalar glueball spectrum
We discuss scenarios for scalar glueballs using arguments based on sum rules,
spectral decomposition, the approximation, the scales of the
strong interaction and the topology of the flux tubes. We analyze the
phenomenological support of those scenarios and their observational
implications. Our investigations hint a rich low lying glueball spectrum.Comment: 11 pages: New title, figure, table and a more detailed comparison
with experiment
Hadronic aspects of exotic baryons
In this talk I look into three different topics, addressing first the
possibility that the is a bound state of , exploiting the
results of this study to find out the contribution of two meson and one baryon
components in the baryon antidecuplet and in the third place I present results
on a new resonant exotic baryonic state which appears as dynamically generated
by the Weinberg Tomozawa interaction.Comment: Talk at the International Workshop PENTAQUARK0
On the determination of quantum numbers and other topics of exotic baryons
In this talk I look into three different topics, addressing first a method to
determine the quantum numbers of the , then exploiting the
possibility that the is a bound state of and in the third
place I present results on a new resonant exotic baryonic state which appears
as dynamically generated by the Weinberg Tomozawa interaction.Comment: 9 pags. Talk in the NSTAR04 Workshop, Grenoble, march 200
Leading SU(3)-breaking corrections to the baryon magnetic moments in Chiral Perturbation Theory
We calculate the baryon magnetic moments using covariant Chiral Perturbation
Theory (PT) within the Extended-on-mass-shell (EOMS) renormalization
scheme. By fitting the two available low-energy constants (LECs), we improve
the Coleman-Glashow description of the data when we include the leading SU(3)
breaking effects coming from the lowest-order loops. This success is in
dramatic contrast with previous attempts at the same order using Heavy Baryon
(HB) PT and covariant Infrared (IR) PT. We also analyze the source
of this improvement with particular attention on the comparison between the
covariant results.Comment: 4 pages, 2 figures, accepted for publication in PR
Neutrino induced threshold production of two pions and N^*(1440) electroweak form factors
We study the threshold production of two pions induced by neutrinos in
nucleon targets. The contribution of nucleon, pion and contact terms are
calculated using a chiral Lagrangian. The contribution of the Roper resonance,
neglected in earlier studies, has also been taken into account. The numerical
results for the cross sections are presented and compared with the available
experimental data. It has been found that in the two pion channels with
and in the final state, the contribution of the
is quite important and could be used to determine the
electroweak transition form factors if experimental data with better statistics
become available in the future.Comment: This version corrects a mistake on the helicity amplitudes sign.
Additional comments on resonance-background relative sign are added. Other
minor corrections. Matches published version. 17 pages, 7 figure
In-medium pi-pi Correlation Induced by Partial Restoration of Chiral Symmetry
We show that both the linear and the non-linear chiral models give an
enhancement of the pi-pi cross section near the 2pi threshold in the
scalar-iso-scalar (I=J=0) channel in nuclear matter. The reduction of the
chiral condensate, i.e., the partial chiral restoration in nuclear matter, is
responsible for the enhancement in both cases. We extract an effective
4pi-nucleon vertex which is responsible for the enhancement but has not been
considered in the non-liear models for in-medium pi-pi interaction. Relation of
this vertex and a next-to-leading order terms in the heavy-baryon chiral
lagrangian, L_piN^(2), is also discussed.Comment: 5 pages, 5 eps figure, REVTe
A solvable model of the genesis of amino-acid sequences via coupled dynamics of folding and slow genetic variation
We study the coupled dynamics of primary and secondary structure formation
(i.e. slow genetic sequence selection and fast folding) in the context of a
solvable microscopic model that includes both short-range steric forces and and
long-range polarity-driven forces. Our solution is based on the diagonalization
of replicated transfer matrices, and leads in the thermodynamic limit to
explicit predictions regarding phase transitions and phase diagrams at genetic
equilibrium. The predicted phenomenology allows for natural physical
interpretations, and finds satisfactory support in numerical simulations.Comment: 51 pages, 13 figures, submitted to J. Phys.
Exponential energy decay of solutions for a system of viscoelastic wave equations of Kirchhoff type with strong damping
The initial boundary value problem for a system of viscoelastic wave
equations of Kirchhoff type with strong damping is considered. We prove that,
under suitable assumptions on relaxation functions and certain initial data,
the decay rate of the solutions energy is exponential
Statistical Mechanics Analysis of LDPC Coding in MIMO Gaussian Channels
Using analytical methods of statistical mechanics, we analyse the typical
behaviour of a multiple-input multiple-output (MIMO) Gaussian channel with
binary inputs under LDPC network coding and joint decoding. The saddle point
equations for the replica symmetric solution are found in particular
realizations of this channel, including a small and large number of
transmitters and receivers. In particular, we examine the cases of a single
transmitter, a single receiver and the symmetric and asymmetric interference
channels. Both dynamical and thermodynamical transitions from the ferromagnetic
solution of perfect decoding to a non-ferromagnetic solution are identified for
the cases considered, marking the practical and theoretical limits of the
system under the current coding scheme. Numerical results are provided, showing
the typical level of improvement/deterioration achieved with respect to the
single transmitter/receiver result, for the various cases.Comment: 25 pages, 7 figure
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