980 research outputs found
Infinite Hopf family of elliptic algebras and bosonization
Elliptic current algebras E_{q,p}(\hat{g}) for arbitrary simply laced finite
dimensional Lie algebra g are defined and their co-algebraic structures are
studied. It is shown that under the Drinfeld like comultiplications, the
algebra E_{q,p}(\hat{g}) is not co-closed for any g. However putting the
algebras E_{q,p}(\hat{g}) with different deformation parameters together, we
can establish a structure of infinite Hopf family of algebras. The level 1
bosonic realization for the algebra E_{q,p}(\hat{g}) is also established.Comment: LaTeX, 11 pages. This is the new and final versio
Note on the Algebra of Screening Currents for the Quantum Deformed W-Algebra
With slight modifications in the zero modes contributions, the positive and
negative screening currents for the quantum deformed W-algebra W_{q,p}(g) can
be put together to form a single algebra which can be regarded as an elliptic
deformation of the universal enveloping algebra of \hat{g}, where g is any
classical simply-laced Lie algebra.Comment: LaTeX file, 9 pages. Errors in Serre relation corrected. Two
references to Awata,H. et al adde
Cosmology in Nonlinear Born-Infeld Scalar Field Theory With Negative Potentials
The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar
field theory with negative potentials was investigated. The cosmological
solutions in some important evolutive epoches were obtained. The different
evolutional behaviors between NLBI and linear(canonical) scalar field theory
have been presented. A notable characteristic is that NLBI scalar field behaves
as ordinary matter nearly the singularity while the linear scalar field behaves
as "stiff" matter. We find that in order to accommodate current observational
accelerating expanding universe the value of potential parameters and
must have an {\it upper bound}. We compare different cosmological
evolutions for different potential parameters .Comment: 18 pages, 18 figures, some references added, revised version for
Int.J.Mod.Phys.A, appeared in Int.J.Mod.Phys.
Vertex--IRF correspondence and factorized L-operators for an elliptic R-operator
As for an elliptic -operator which satisfies the Yang--Baxter equation,
the incoming and outgoing intertwining vectors are constructed, and the
vertex--IRF correspondence for the elliptic -operator is obtained. The
vertex--IRF correspondence implies that the Boltzmann weights of the IRF model
satisfy the star--triangle relation. By means of these intertwining vectors,
the factorized L-operators for the elliptic -operator are also constructed.
The vertex--IRF correspondence and the factorized L-operators for Belavin's
-matrix are reproduced from those of the elliptic -operator.Comment: 25 pages, amslatex, no figure
Dynamical differential equations compatible with rational qKZ equations
For the Lie algebra we introduce a system of differential operators
called the dynamical operators. We prove that the dynamical differential
operators commute with the rational quantized Knizhnik-Zamolodchikov
difference operators. We describe the transformations of the dynamical
operators under the natural action of the Weyl group.Comment: 7 pages, AmsLaTe
Dynamics of Symmetry Breaking and Tachyonic Preheating
We reconsider the old problem of the dynamics of spontaneous symmetry
breaking using 3d lattice simulations, and develop a theory of tachyonic
preheating, which occurs due to the spinodal instability of the scalar field.
Tachyonic preheating is so efficient that symmetry breaking typically completes
within a single oscillation of the field distribution as it rolls towards the
minimum of its effective potential. As an application of this theory we
consider preheating in the hybrid inflation scenario, including SUSY-motivated
F-term and D-term inflationary models. We show that preheating in hybrid
inflation is typically tachyonic and the stage of oscillations of a homogeneous
component of the scalar fields driving inflation ends after a single
oscillation. Our results may also be relevant for the theory of the formation
of disoriented chiral condensates in heavy ion collisions.Comment: 7 pages, 6 figures. Higher quality figures and computer generated
movies in gif format illustrating our results can be found at
http://physics.stanford.edu/gfelder/hybri
The SIEA SHRIMP flap: An ultrathin axial pattern free flap useable in obese patients
The reconstruction of distal extremity wounds poses a unique surgical challenge. In free tissue transfer, a thin, pliable skin flap is the ideal. Obese patients have a paucity of thin skin donor sites. Herein we report the discovery of a free SHRIMP flap (Superthin Harvest of a Reliable Islanded Medial Pannus flap) based on the SIEA vessels, harvested from a thick abdominal pannus at the time of cosmetic abdominoplasty. A 61-year-old woman with a chronic wound of the right Achilles tendon was evaluated for reconstruction after failing conservative measures. At the time of consultation, the patient expressed interest in abdominoplasty. Therefore, a skin flap from the abdomen or rectus abdominis muscle flap in the context of an abdominoplasty was offered. Despite obesity affecting the pannus, the superficial inferior epigastric vessels were found to course superficially beneath the dermis at time of abdominoplasty. This allowed straightforward harvest of a superthin flap of skin and minimal subcutaneous fat, which contoured to the ankle with an aesthetically pleasing outcome. The patient was satisfied with the results of her abdominoplasty and coverage of her chronic wound. The SHRIMP flap provides a straightforward, axial pattern, superthin free skin flap based on the superficial inferior epigastric vessels, and represents a useful option in obese patients. The flap can be combined with abdominoplasty for an aesthetic donor site
Limb bone scaling in hopping diprotodonts and quadrupedal artiodactyls
Bone adaptation is modulated by the timing, direction, rate, and magnitude of mechanical loads. To investigate whether frequent slow, or infrequent fast, gaits could dominate bone adaptation to load, we compared scaling of the limb bones from two mammalian herbivore clades that use radically different high-speed gaits, bipedal hopping and quadrupedal galloping. Forelimb and hindlimb bones were collected from 20 artiodactyl and 15 diprotodont species (body mass M 1.05 - 1536 kg) and scanned in clinical computed tomography or X-ray microtomography. Second moment of area (Imax) and bone length (l) were measured. Scaling relations (y = axb) were calculated for l vs M for each bone and for Imax vs M and Imax vs l for every 5% of length. Imax vs M scaling relationships were broadly similar between clades despite the diprotodont forelimb being nearly unloaded, and the hindlimb highly loaded, during bipedal hopping. Imax vs l and l vs M scaling were related to locomotor and behavioural specialisations. Low-intensity loads may be sufficient to maintain bone mass across a wide range of species. Occasional high-intensity gaits might not break through the load sensitivity saturation engendered by frequent low-intensity gaits
Preheating in Supersymmetric Theories
We examine the particle production via preheating at the end of inflation in
supersymmetric theories. The inflaton and matter scalars are now necessarily
complex fields, and their relevant interactions are restricted by holomorphy.
In general this leads to major changes both in the inflaton dynamics and in the
efficiency of the preheating process. In addition, supersymmetric models
generically contain multiple isolated vacua, raising the possibility of
non-thermal production of dangerous topological defects. Because of these
effects, the success of leptogenesis or WIMPZILLA production via preheating
depends much more sensitively on the detailed parameters in the inflaton sector
than previously thought.Comment: 24 pages, 3 figures; references adde
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