215 research outputs found
Proper-time methods in the presence of non-constant background fields
A formalism is developed to enable the construction of the effective action
and related quantities in QED for the case of time-varying background electric
fields. Some examples are studied and evidence is sought for a possible
transition to a phase in which chiral symmetry is spontaneously broken.
YCTP-P14-94Comment: 13 pages, YCTP-P14-9
Reality of Complex Affine Toda Solitons
There are infinitely many topological solitons in any given complex affine
Toda theories and most of them have complex energy density. When we require the
energy density of the solitons to be real, we find that the reality condition
is related to a simple ``pairing condition.'' Unfortunately, rather few soliton
solutions in these theories survive the reality constraint, especially if one
also demands positivity. The resulting implications for the physical
applicability of these theories are briefly discussed.Comment: LaTeX, 15 pages, UBTH-049
The Rho-Meson as a Collective Excitation
A model of the rho-meson as a collective excitation of pairs in a
system that obeys the modified Nambu--Jona-Lasinio Lagrangian is proposed. The
rho emerges as a dormant Goldstone boson. The origin of the rho-meson mass is
understood as a result of spontaneous chiral symmetry breaking. The low-energy
dynamics of rho, pi, omega and gamma is consistently described in this new
framework. The model accounts for the origin of the celebrated
Kawarabayashi--Suzuki--Riazuddin--Fayyazuddin relation.Comment: 8 pages, plain LaTe
Large Weinberg-Tomozawa interaction and spin-flavor symmetry
The construction of an extended version of the Weinberg-Tomozawa Lagrangian,
in which baryons and mesons form spin-flavor multiplets, is reviewed and some
of its properties discussed, for an arbitrary number of colors and flavors. The
coefficient tables of spin-flavor irreducible representations related by
crossing between the -, - and -channels are explicitly constructed.Comment: 3 pages, no figures. Presented at the IVth International Conference
on Quarks and Nuclear Physics, Madrid, June 5th-10th 200
Low-lying even parity meson resonances and spin-flavor symmetry
A study is presented of the wave meson-meson interactions involving
members of the nonet and of the octet. The starting point is an
SU(6) spin-flavor extension of the SU(3) flavor Weinberg-Tomozawa Lagrangian.
SU(6) symmetry breaking terms are then included to account for the physical
meson masses and decay constants, while preserving partial conservation of the
axial current in the light pseudoscalar sector. Next, the matrix amplitudes
are obtained by solving the Bethe Salpeter equation in coupled-channel with the
kernel built from the above interactions. The poles found on the first and
second Riemann sheets of the amplitudes are identified with their possible
Particle Data Group (PDG) counterparts. It is shown that most of the low-lying
even parity PDG meson resonances, specially in the and sectors,
can be classified according to multiplets of the spin-flavor symmetry group
SU(6). The , and some resonances cannot be
accommodated within this SU(6) scheme and thus they would be clear candidates
to be glueballs or hybrids. Finally, we predict the existence of five exotic
resonances ( and/or ) with masses in the range 1.4--1.6 GeV,
which would complete the , , and multiplets of
SU(3)SU(2).Comment: 43 pages, 2 figures, 61 tables. Improved discussion of Section II. To
appear in Physical Review
Dimensional Reduction and Dynamical Chiral Symmetry Breaking by a Magnetic Field in Dimensions
It is shown that in dimensions, a constant magnetic field is a catalyst
of dynamical chiral symmetry breaking, leading to generating a fermion mass
even at the weakest attractive interaction between fermions. The essence of
this effect is the dimensional reduction () in the dynamics of fermion pairing in a magnetic field. The effect is
illustrated in the Nambu-Jona-Lasinio model. Possible applications of this
effect are briefly discussed.Comment: 13 pages, LaTeX, no figure
Strong and Electromagnetic Decays of the Baryon Decuplet
We discuss the strong and radiative decays of the decuplet of baryon
resonances to the baryon octet in chiral perturbation theory. We comment on the
implications for the polarisability of the nucleon.Comment: 16 pages + 5 figures (.ps files) appended to file. Uses tables.tex
and harvmac.te
Up-scaling a Sol-Gel Process for the Production of a Multi-Component Xerogel Powder
A sol-gel process for the synthesis of a multi-component oxide material from the system SiO2-ZrO2-Al2O3underwent optimization and up-scaling. Initially, on a laboratory scale, components including precursors, catalysts, and additives were methodically evaluated to ensure a safe and efficient transition to larger volumes. Subsequently, the equipment for the whole setup of the sol-gel process was strategically selected. Leveraging insights from these optimizations, the process was successfully scaled-up to pilot-scale operation, conducting hydrolysis, condensation reactions, gelation, aging, and drying within a single, integrated conical dryer system for an 80 L batch. A visual test and FTIR spectroscopy were applied for process control and monitoring
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