1,027 research outputs found
On the relationship of the scaled phase space and Skyrme-coherent state treatments of proton antiproton annihilation at rest
We discuss pion multiplicities and single pion momentum spectra from proton
antiproton annihilation at rest. Both the scaled phase space model and the
Skyrme-coherent state approach describe these observables well. In the coherent
state approach the puzzling size of the scale parameter relating the phase
space integrals for different multiplicities is replaced by a well defined
weight function. The strength of this function is determined by the intensity
of the classical pion field and its spatial extent is of order 1 fm.Comment: 11 pages including 4 figures(postscript
New ground-based observational methods and instrumentation for asteroseismology
Space instrumentation like SOHO, MOST, CoRoT and Kepler has been and is being
built to attain very high precision data to be used for asteroseismic analysis.
Nonetheless, there is a very strong need for providing additional information,
especially on mode identification. With this contribution I will review the
efforts been put on new ground-based instrumentation and the methodology that
can be used to achieve this aim.Comment: 6 pages. Review contribution to be published in Astrophysics and
Space Science Proceedings series (ASSP), in the proceedings of "20th Stellar
Pulsation Conference Series: Impact of new instrumentation and new insights
in stellar pulsations", 5-9 September 2011, Granada, Spai
A study of local approximation for polarization potentials
We discuss the derivation of an equivalent \textit{l}-independent
polarization potential for use in the optical Schr\"{o}dinger equation that
describes the elastic scattering of heavy ions. Three diffferent methods are
used for this purpose. Application of our theory to the low energy scattering
of the halo nucleus Li from a C target is made. It is found that
the notion of \textit{l}-independent polarization potential has some validity
but can not be a good substitute for the \textit{l}-dependent local equivalent
Feshbach polarization potential.Comment: 8 pages, 4 figure
Matrix Hamiltonians: SUSY approach to hidden symmetries
A new supersymmetric approach to the analysis of dynamical symmetries for
matrix quantum systems is presented. Contrary to standard one dimensional
quantum mechanics where there is no role for an additional symmetry due to
nondegeneracy, matrix hamiltonians allow for non-trivial residual symmetries.
This approach is based on a generalization of the intertwining relations
familiar in SUSY Quantum Mechanics. The corresponding matrix supercharges, of
first or of second order in derivatives, lead to an algebra which incorporates
an additional block diagonal differential matrix operator (referred to as a
"hidden" symmetry operator) found to commute with the superhamiltonian. We
discuss some physical interpretations of such dynamical systems in terms of
spin 1/2 particle in a magnetic field or in terms of coupled channel problem.
Particular attention is paid to the case of transparent matrix potentials.Comment: 20 pages, LaTe
Skyrmions and the Nuclear Force
The derivation of the nucleon-nucleon force from the Skyrme model is
reexamined. Starting from previous results for the potential energy of
quasistatic solutions, we show that a calculation using the Born-Oppenheimer
approximation properly taking into account the mixing of nucleon resonances,
leads to substantial central attraction. We obtain a potential that is in
qualitative agreement with phenomenological potentials. We also study the
non-adiabatic corrections, such as the velocity dependent transition
potentials, and discuss their importance.Comment: 24 pages, UPR-0124M
Unitary ambiguity in the extraction of the E2/M1 ratio for the transition
The resonant electric quadrupole amplitude in the transition is of great interest for the understanding of
baryon structure. Various dynamical models have been developed to extract it
from the corresponding photoproduction multipole of pions on nucleons. It is
shown that once such a model is specified, a whole class of unitarily
equivalent models can be constructed, all of them providing exactly the same
fit to the experimental data. However, they may predict quite different
resonant amplitudes. Therefore, the extraction of the E2/M1() ratio (bare or dressed) which is based on a dynamical
model using a largely phenomenological interaction is not unique.Comment: 10 pages revtex including 4 postscript figure
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