81,452 research outputs found
Meson decay in the Fock-Tani Formalism
The Fock-Tani formalism is a first principle method to obtain effective
interactions from microscopic Hamiltonians. Usually this formalism was applied
to scattering, here we introduced it to calculate partial decay widths for
mesons.Comment: Presented at HADRON05 XI. "International Conference on Hadron
Spectroscopy" Rio de Janeiro, Brazil, August 21 to 26, 200
Meson decay in a corrected model
Extensively applied to both light and heavy meson decay and standing as one
of the most successful strong decay models is the model, in which
pair production is the dominant mechanism. The pair production can
be obtained from the non-relativistic limit of a microscopic interaction
Hamiltonian involving Dirac quark fields. The evaluation of the decay amplitude
can be performed by a diagrammatic technique for drawing quark lines. In this
paper we use an alternative approach which consists in a mapping technique, the
Fock-Tani formalism, in order to obtain an effective Hamiltonian starting from
same microscopic interaction. An additional effect is manifest in this
formalism associated to the extended nature of mesons: bound-state corrections.
A corrected is obtained and applied, as an example, to
and decays.Comment: 3 figures. To appear in Physical Review
Labyrinthine pathways towards supercycle attractors in unimodal maps
We uncover previously unknown properties of the family of periodic
superstable cycles in unimodal maps characterized each by a Lyapunov exponent
that diverges to minus infinity. Amongst the main novel properties are the
following: i) The basins of attraction for the phases of the cycles develop
fractal boundaries of increasing complexity as the period-doubling structure
advances towards the transition to chaos. ii) The fractal boundaries, formed by
the preimages of the repellor, display hierarchical structures organized
according to exponential clusterings that manifest in the dynamics as
sensitivity to the final state and transient chaos. iii) There is a functional
composition renormalization group (RG) fixed-point map associated to the family
of supercycles. iv) This map is given in closed form by the same kind of
-exponential function found for both the pitchfork and tangent bifurcation
attractors. v) There is a final stage ultra-fast dynamics towards the attractor
with a sensitivity to initial conditions that decreases as an exponential of an
exponential of time.Comment: 8 pages, 13 figure
Interpolation of bilinear operators and compactness
The behavior of bilinear operators acting on interpolation of Banach spaces
for the method in relation to the compactness is analyzed. Similar
results of Lions-Peetre, Hayakawa and Person's compactness theorems are
obtained for the bilinear case and the method.Comment: This work was published at "Nonlinear Analysis: Theory, Methods and
Applications, Volume 73, Issue 2, 2010, Pages 526-537". Since there are some
gaps in the original proof of Theorem 4.3, Here we give a new proof. For
this, we change the Lemma 4.
The two membranes problem for different operators
We study the two membranes problem for different operators, possibly
nonlocal. We prove a general result about the H\"older continuity of the
solutions and we develop a viscosity solution approach to this problem. Then we
obtain regularity of the solutions provided that the orders of
the two operators are different. In the special case when one operator
coincides with the fractional Laplacian, we obtain the optimal regularity and a
characterization of the free boundary
An evolutionary model for GHz Peaked Spectrum Sources. Predictions for high frequency surveys
We have explored, in the general framework of the ``young source'' scenario,
evolutionary models for GHz Peaked Spectrum (GPS) galaxies and quasars which
reproduce the observed counts, redshift and peak frequency distributions of
currently available samples. Substantially different cosmological evolution
properties are found for the two populations: the quasar luminosity function
must evolve strongly up to , while the data on galaxies may be
consistent with no evolution. The models show that GPS sources (mostly quasars)
may comprise quite a significant fraction of bright (Jy) radio sources
at GHz if the intrinsic distribution of peak frequencies extends
up to GHz. In any case, however, their fraction decreases rapidly
with decreasing flux and their contribution to small scale fluctuations in the
frequency range covered by the forthcoming space missions MAP and Planck
Surveyor is expected to be minor.Comment: 7 pages, 4 figures, A&A accepte
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