1,110 research outputs found
Slow equivariant lump dynamics on the two sphere
The low-energy, rotationally equivariant dynamics of n CP^1 lumps on S^2 is
studied within the approximation of geodesic motion in the moduli space of
static solutions. The volume and curvature properties of this moduli space are
computed. By lifting the geodesic flow to the completion of an n-fold cover of
the moduli space, a good understanding of nearly singular lump dynamics within
this approximation is obtained.Comment: 12 pages, 3 figure
Formation of singularities for equivariant 2+1 dimensional wave maps into the two-sphere
In this paper we report on numerical studies of the Cauchy problem for
equivariant wave maps from 2+1 dimensional Minkowski spacetime into the
two-sphere. Our results provide strong evidence for the conjecture that large
energy initial data develop singularities in finite time and that singularity
formation has the universal form of adiabatic shrinking of the degree-one
harmonic map from into .Comment: 14 pages, 5 figures, final version to be published in Nonlinearit
Supersymmetric WZW Model on Full and Half Plane
We study classical integrability of the supersymmetric U(N) model
with the Wess-Zumino-Witten term on full and half plane. We demonstrate the
existence of nonlocal conserved currents of the model and derive general
recursion relations for the infinite number of the corresponding charges in a
superfield framework. The explicit form of the first few supersymmetric charges
are constructed. We show that the considered model is integrable on full plane
as a concequence of the conservation of the supersymmetric charges. Also, we
study the model on half plane with free boundary, and examine the conservation
of the supersymmetric charges on half plane and find that they are conserved as
a result of the equations of motion and the free boundary condition. As a
result, the model on half plane with free boundary is integrable. Finally, we
conclude the paper and some features and comments are presented.Comment: 12 pages. submitted to IJMP
The Casimir energy of skyrmions in the 2+1-dimensional O(3)-model
One-loop quantum corrections to the classical vortices in 2+1 dimensional
O(3)-models are evaluated. Skyrme and Zeeman potential terms are used to
stabilize the size of topological solitons. Contributions from zero modes,
bound-states and scattering phase-shifts are calculated for vortices with
winding index n=1 and n=2. For both cases the S-matrix shows a pronounced
series of resonances for magnon-vortex scattering in analogy to the
well-established baryon resonances in hadron physics, while vortices with n>2
are already classically unstable against decay. The quantum corrections
destabilize the classically bound n=2 configuration. Approximate independence
of the results with respect to changes in the renormalization scale is
demonstrated.Comment: 24 pages LaTeX, 14 figure
Magnetothermodynamics of BPS baby skyrmions
The magnetothermodynamics of skyrmion type matter described by the gauged BPS
baby Skyrme model at zero temperature is investigated. We prove that the BPS
property of the model is preserved also for boundary conditions corresponding
to an asymptotically constant magnetic field. The BPS bound and the
corresponding BPS equations saturating the bound are found. Further, we show
that one may introduce pressure in the gauged model by a redefinition of the
superpotential. Interestingly, this is related to non-extremal type solutions
in the so-called fake supersymmetry method. Finally, we compute the equation of
state of magnetized BSP baby skyrmions inserted into an external constant
magnetic field and under external pressure , i.e., , where
is the "volume" (area) occupied by the skyrmions. We show that the BPS baby
skyrmions form a ferromagnetic medium.Comment: Latex, 39 pages, 14 figures. v2: New results and references added,
physical interpretation partly change
Postâdischarge tobacco cessation rates among hospitalized US veterans with and without diabetes
Aimsâ Smoking is a major risk factor for cardiovascular complications among patients with diabetes. Hospitalization has been shown to enhance cessation rates. The purpose of this study was to compare 6âmonth postâhospitalization tobacco cessation rates among US veterans with and without diabetes. Methodsâ This was a longitudinal study among inpatient veterans who used tobacco in the past month ( n â=â496). Patients were recruited and surveyed from three Midwestern Department of Veterans Affairs hospitals during an acuteâcare hospitalization. They were also asked to complete a followâup survey 6âmonths postâdischarge. Bivariateâ and multivariableâadjusted analyses were conducted to determine differences in tobacco cessation rates between patients with and without a diagnosis of diabetes. Resultsâ The mean age of patients was 55.2âyears and 62% were white. Twentyânine per cent had coâmorbid diabetes. A total of 18.8% of patients with diabetes reported tobacco cessation at 6âmonths compared with 10.9% of those without diabetes ( P â=â0.02). Cotinineâverified cessation rates were 12.5 vs. 7.4% in the groups with and without diabetes, respectively ( P â=â0.07). Controlling for psychiatric coâmorbidities, depressive symptoms, age, selfârated health and nicotine dependence, the multivariableâadjusted logistic regression showed that patients with diabetes had three times higher odds of 6âmonth cotinineâverified tobacco cessation as compared with those without diabetes (odds ratioâ3.17, P â=â0.005). Conclusionsâ Postâhospitalization rates of smoking cessation are high among those with diabetes. Intensive tobacco cessation programmes may increase these cessation rates further.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92145/1/j.1464-5491.2012.03635.x.pd
A geometric interpretation of the spectral parameter for surfaces of constant mean curvature
Considering the kinematics of the moving frame associated with a constant
mean curvature surface immersed in S^3 we derive a linear problem with the
spectral parameter corresponding to elliptic sinh-Gordon equation. The spectral
parameter is related to the radius R of the sphere S^3. The application of the
Sym formula to this linear problem yields constant mean curvature surfaces in
E^3. Independently, we show that the Sym formula itself can be derived by an
appropriate limiting process R -> infinity.Comment: 12 page
New Integrable Sectors in Skyrme and 4-dimensional CP^n Model
The application of a weak integrability concept to the Skyrme and
models in 4 dimensions is investigated. A new integrable subsystem of the
Skyrme model, allowing also for non-holomorphic solutions, is derived. This
procedure can be applied to the massive Skyrme model, as well. Moreover, an
example of a family of chiral Lagrangians providing exact, finite energy
Skyrme-like solitons with arbitrary value of the topological charge, is given.
In the case of models a tower of integrable subsystems is obtained. In
particular, in (2+1) dimensions a one-to-one correspondence between the
standard integrable submodel and the BPS sector is proved. Additionally, it is
shown that weak integrable submodels allow also for non-BPS solutions.
Geometric as well as algebraic interpretations of the integrability conditions
are also given.Comment: 23 page
A Skyrme-type proposal for baryonic matter
The Skyrme model is a low-energy effective field theory for QCD, where the
baryons emerge as soliton solutions. It is, however, not so easy within the
standard Skyrme model to reproduce the almost exact linear growth of the
nuclear masses with the baryon number (topological charge), due to the lack of
Bogomolny solutions in this model, which has also hindered analytical progress.
Here we identify a submodel within the Skyrme-type low energy effective action
which does have a Bogomolny bound and exact Bogomolny solutions, and therefore,
at least at the classical level, reproduces the nuclear masses by construction.
Due to its high symmetry, this model qualitatively reproduces the main features
of the liquid droplet model of nuclei. Finally, we discuss under which
circumstances the proposed sextic term, which is of an essentially geometric
and topological nature, can be expected to give a reasonable description of
properties of nuclei.Comment: 11 pages, 2 figures, latex. v3: Extended and revised version, some
clarifications added. Some references and 2 figures added. v4: matches
published versio
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