1,268 research outputs found
Baby Skyrmion chains
Previous results on multi-charged Baby Skyrmion solutions have pointed to a
modular structure, comprised of charge two rings and single charge one
Skyrmions, which combine to form higher charged structures. In this paper we
present numerical evidence which shows an alternative finite chain,
multi-charged global energy minimum Baby Skymion solution. We then proceed from
the infinite plane, to Baby Skyrmions on a cylinder and then a torus, to obtain
the solutions of periodic Baby Skyrmions, of which periodic segments will
correspond to sections of large charge Baby Skyrmions in the plane
Resonances, and mechanisms of Theta-production
After explaining necessity of exotic hadrons, we discuss mechanisms which
could determine production of the exotic Theta-baryon. A possible important
role of resonances (producing the Theta in real or virtual decays) is
emphasized for various processes. Several experimental directions for studies
of such resonances, and the Theta itself, are suggested. We briefly discuss
also recent negative results on the Theta-baryon.Comment: 6 page
Spectra of Free Diquark in the Bethe-Salpeter Approach
In this work, we employ the Bethe-Salpeter (B-S) equation to investigate the
spectra of free diquarks and their B-S wave functions. We find that the B-S
approach can be consistently applied to study the diqaurks with two heavy
quarks or one heavy and one light quarks, but for two light-quark systems, the
results are not reliable. There are a few free parameters in the whole scenario
which can only be fixed phenomenologically. Thus, to determine them, one has to
study baryons which are composed of quarks and diquarks.Comment: 16 pages, no figure
-Dimensional Large QCD coupled to Adjoint Fermions
We consider 1+1-dimensional QCD coupled to Majorana fermions in the adjoint
representation of the gauge group . Pair creation of partons (fermion
quanta) is not suppressed in the large- limit, where the glueball-like bound
states become free. In this limit the spectrum is given by a linear \lc\ Schr\"
odinger equation, which we study numerically using the discretized \lcq. We
find a discrete spectrum of bound states, with the logarithm of the level
density growing approximately linearly with the mass. The wave function of a
typical excited state is a complicated mixture of components with different
parton numbers. A few low-lying states, however, are surprisingly close to
being eigenstates of the parton number, and their masses can be accurately
calculated by truncated diagonalizations.Comment: 22 pages + 9 figures (available by request from
[email protected]), uses phyzzx.tex + tables.tex PUPT-1413,
IASSNS-HEP-93/4
Brane Gases in the Early Universe
Over the past decade it has become clear that fundamental strings are not the
only fundamental degrees of freedom in string theory. D-branes are also part of
the spectrum of fundamental states. In this paper we explore some possible
effects of D-branes on early Universe string cosmology, starting with two key
assumptions: firstly that the initial state of the Universe corresponded to a
dense, hot gas in which all degrees of freedom were in thermal equilibrium, and
secondly that the topology of the background space admits one-cycles. We argue
by t-duality that in this context the cosmological singularities are not
present. We derive the equation of state of the brane gases and apply the
results to suggest that, in an expanding background, the winding modes of
fundamental strings will play the most important role at late times. In
particular, we argue that the string winding modes will only allow four
space-time dimensions to become large. The presence of brane winding modes with
may lead to a hierarchy in the sizes of the extra dimensions.Comment: 8 pages, 1 figure; typos corrected; published in PR
Small Momentum Evolution of the Extended Drell--Hearn--Gerasimov Sum Rule
We investigate the momentum dependence of the extended Drell-Hearn-Gerasimov
sum rule. An economical formalism is developed which allows to express the
extended DHG sum rule in terms of a single virtual Compton amplitude in forward
direction. Rigorous results for the small momentum evolution are derived from
chiral perturbation theory within the one-loop approximation. Furthermore, we
evaluate some higher order contributions arising from
intermediate states and relativistic corrections. (2 figures available upon
request).Comment: 12 pages, TeX, BUTP-92/51 and CRN-92-5
Updated resonance photo-decay amplitudes to 2 GeV
We present the results of an energy-dependent and set of single-energy
partial-wave analyses of single-pion photoproduction data. These analyses
extend from threshold to 2 GeV in the laboratory photon energy, and update our
previous analyses to 1.8 GeV. Photo-decay amplitudes are extracted for the
baryon resonances within this energy range. We consider two photoproduction sum
rules and the contributions of two additional resonance candidates found in our
most recent analysis of elastic scattering data. Comparisons are made
with previous analyses.Comment: Revtex, 26 pages, 3 figures. Postscript figures available from
ftp://clsaid.phys.vt.edu/pub/pr or indirectly from
http://clsaid.phys.vt.edu/~CAPS
Polarization Phenomena in Small-Angle Photoproduction of e+e- Pairs and the Gerasimov-Drell-Hearn Sum Rule
Photoproduction of pairs at small angles is investigated as a tool
to determine the functions and entering the real-photon forward
Compton scattering amplitude. The method is based on an interference of the
Bethe-Heitler and the virtual Compton scattering mechanisms, generating an
azimuthal asymmetry in the versus yield. The general case of a
circularly polarized beam and a longitudinally polarized target allows one to
determine both the real and imaginary parts of as well as . The
imaginary part of requires target polarization only. We calculate cross
sections and asymmetries of the reaction , estimate
corrections and backgrounds, and propose suitable kinematical regions to
perform the experiment. Our investigation shows that photoproduction of
-pairs off the proton and light nuclei may serve as a rather sensitive
test of the validity of the Gerasimov-Drell-Hearn sum rule.Comment: 22 pages; revtex; 5 postscript figures included in submission;
submitted to Phys. Rev.
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