220 research outputs found
Average formation lengths of baryons and antibaryons in string model
In this work it is continued the investigation of the space-time scales of
the hadronization process in the framework of string model. The average
formation lengths of several widely using species of baryons (antibaryons) such
as (), (), (),
() and () are studied. It is shown that
they depend from electrical charges or, more precise, from quark contents of
the hadrons. In particular, the average formation lengths of positively charged
hadrons, for example protons, are considerably larger than of their negatively
charged antiparticles, antiprotons. This statement is fulfilled for all nuclear
targets and any value of the Bjorken scaling variable . The main
mechanism is direct production. Additional production mechanism in result of
decay of resonances gives small contribution. It is shown that the average
formation lengths of protons (antiprotons) are slowly rising (decreasing)
functions of , the ones of neutrons and antineutrons are slowly
decreasing functions of . The shape and behavior of average formation
lengths for baryons qualitatively coincide with the ones for pseudoscalar
mesons obtained earlier.Comment: 7 pages, 6 figure
Average formation length in string model
The space-time scales of the hadronization process in the framework of string
model are investigated. It is shown that the average formation lengths of
pseudoscalar mesons, produced in semi-inclusive deep inelastic scattering (DIS)
of leptons on different targets, depend from their electrical charges. In
particular the average formation lengths of positively charged hadrons are
larger than of negatively charged ones. This statement is fulfiled for all
using scaling functions, for (the fraction of the virtual photon energy
transferred to the detected hadron) larger than 0.15, for all nuclear targets
and any value of the Bjorken scaling variable . In all cases, the main
mechanism is direct production of pseudoscalar mesons. Including in
consideration additional mechanism of production in result of decay of
resonances, leads to decrease of average formation lengths. It is shown that
the average formation lengths of positively (negatively) charged mesons are
slowly rising (decreasing) functions of . The obtained results can be
important, in particular, for the understanding of the hadronization process in
nuclear environment
Scalar field critical collapse in 2+1 dimensions
We carry out numerical experiments in the critical collapse of a spherically
symmetric massless scalar field in 2+1 spacetime dimensions in the presence of
a negative cosmological constant and compare them against a new theoretical
model. We approximate the true critical solution as the Garfinkle
solution, matched at the lightcone to a Vaidya-like solution, and corrected to
leading order for the effect of . This approximation is only
at the lightcone and has three growing modes. We {\em conjecture} that
pointwise it is a good approximation to a yet unknown true critical solution
that is analytic with only one growing mode (itself approximated by the top
mode of our amended Garfinkle solution). With this conjecture, we predict a
Ricci-scaling exponent of and a mass-scaling exponent of
, compatible with our numerical experiments.Comment: 27 page
Nonlinear perturbations of the Kaluza-Klein monopole
We consider the nonlinear stability of the Kaluza-Klein monopole viewed as
the static solution of the five dimensional vacuum Einstein equations. Using
both numerical and analytical methods we give evidence that the Kaluza-Klein
monopole is asymptotically stable within the cohomogeneity-two biaxial Bianchi
IX ansatz recently introduced in \cite{bcs}. We also show that for sufficiently
large perturbations the Kaluza-Klein monopole loses stability and collapses to
a Kaluza-Klein black hole. The relevance of our results for the stability of
BPS states in M/String theory is briefly discussed.Comment: 4 pages, 4 figure
Anomalously small wave tails in higher dimensions
We consider the late-time tails of spherical waves propagating on
even-dimensional Minkowski spacetime under the influence of a long range radial
potential. We show that in six and higher even dimensions there exist
exceptional potentials for which the tail has an anomalously small amplitude
and fast decay. Along the way we clarify and amend some confounding arguments
and statements in the literature of the subject.Comment: 13 page
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