3,818 research outputs found
Quantum Corrections to Q-Balls
We extend calculational techniques for static solitons to the case of field
configurations with simple time dependence in order to consider quantum effects
on the stability of Q-balls. These nontopological solitons exist classically
for any fixed value of an unbroken global charge Q. We show that one-loop
quantum effects can destabilize very small Q-balls. We show how the properties
of the soliton are reflected in the associated scattering problem, and find
that a good approximation to the full one-loop quantum energy of a Q-ball is
given by , where is the frequency of the classical
soliton's time dependence, and is the energy of the lowest bound state in
the associated scattering problem.Comment: 6 pages, 2 figures, uses RevTex4; v2: replaced figure
Heavy Fermion Stabilization of Solitons in 1+1 Dimensions
We find static solitons stabilized by quantum corrections in a
(1+1)-dimensional model with a scalar field chirally coupled to fermions. This
model does not support classical solitons. We compute the renormalized energy
functional including one-loop quantum corrections. We carry out a variational
search for a configuration that minimizes the energy functional. We find a
nontrivial configuration with fermion number whose energy is lower than the
same number of free fermions quantized about the translationally invariant
vacuum. In order to compute the quantum corrections for a given background
field we use a phase-shift parameterization of the Casimir energy. We identify
orders of the Born series for the phase shift with perturbative Feynman
diagrams in order to renormalize the Casimir energy using perturbatively
determined counterterms. Generalizing dimensional regularization, we
demonstrate that this procedure yields a finite and unambiguous energy
functional.Comment: 27 papes Latex, equation labels corrected, version to be published in
Nucl. Phys.
A Heavy Fermion Can Create a Soliton: A 1+1 Dimensional Example
We show that quantum effects can stabilize a soliton in a model with no
soliton at the classical level. The model has a scalar field chirally coupled
to a fermion in 1+1 dimensions. We use a formalism that allows us to calculate
the exact one loop fermion contribution to the effective energy for a spatially
varying scalar background. This energy includes the contribution from
counterterms fixed in the perturbative sector of the theory. The resulting
energy is therefore finite and unambiguous. A variational search then yields a
fermion number one configuration whose energy is below that of a single free
fermion.Comment: 10 pages, RevTeX, 2 figures composed from 4 .eps files; v2: fixed
minor errors, added reference; v3: corrected reference added in v
Electron Optics
Contains research objectives and summary of research on one research project.Joint Services Electronics Program (Contract DAAB07-75-C-1346
Nonlinear Fluid Dynamics Description of non-Newtonian Fluids
Nonlinear hydrodynamic equations for visco-elastic media are discussed. We
start from the recently derived fully hydrodynamic nonlinear description of
permanent elasticity that utilizes the (Eulerian) strain tensor. The reversible
quadratic nonlinearities in the strain tensor dynamics are of the 'lower
convected' type, unambiguously. Replacing the (often neglected) strain
diffusion by a relaxation of the strain as a minimal ingredient, a generalized
hydrodynamic description of viscoelasticity is obtained. This can be used to
get a nonlinear dynamic equation for the stress tensor (sometimes called
constitutive equation) in terms of a power series in the variables. The form of
this equation and in particular the form of the nonlinear convective term is
not universal but depends on various material parameters. A comparison with
existing phenomenological models is given. In particular we discuss how these
ad-hoc models fit into the hydrodynamic description and where the various
non-Newtonian contributions are coming from.Comment: Acta Rheologic
Spin wave mediated non-reciprocal effects in antiferromagnets
By using an effective field theory for the electromagnetic interaction of
spin waves, we show that, in certain antiferromagnets, the latter induce
non-reciprocal effects in the microwave region, which should be observable in
the second harmonic generation and produce gyrotropic birefringency. We
calculate the various (non-linear) susceptibilities in terms of a few
parameters the order of magnitude of which is under control.Comment: Latex file, 22p . Published versio
Electron Optics
Contains reports on two research projects.Joint Services Electronics Program (Contract DAAB07-75-C-1346
Numerical Simulation of an Electroweak Oscillon
Numerical simulations of the bosonic sector of the
electroweak Standard Model in 3+1 dimensions have demonstrated the existence of
an oscillon -- an extremely long-lived, localized, oscillatory solution to the
equations of motion -- when the Higgs mass is equal to twice the boson
mass. It contains total energy roughly 30 TeV localized in a region of radius
0.05 fm. A detailed description of these numerical results is presented.Comment: 12 pages, 8 figures, uses RevTeX4; v2: expanded results section,
fixed typo
Emergencies within hospital wards: An observational study of the non-technical skills of medical emergency teams
Background Medical emergency teams are essential in responding to acute deterioration of patients in hospitals, requiring both clinical and non-technical skills. This study aims to assess the non-technical skills of medical emergency teams during hospital ward emergencies and explore team members perceptions and experiences of the use non-technical skills during medical emergencies. Methods A multi-methods study was conducted in two phases. During phase one observation and assessment of non-technical skills used in medical emergencies using the Team Emergency Assessment Measure (TEAMâą) was conducted; and in the phase two in-depth interviews were undertaken with medical emergency team members. Results Based on 20 observations, mean TEAMâą ratings for non-technical skill domains were: âleadershipâ 5.0 out of 8 (±2.0); âteamworkâ 21.6 out of 28 (±3.6); and âtask managementâ 6.5 out of 8 (±1.4). The mean âglobalâ score was 7.5 out of 10 (±1.5). The qualitative findings identified three areas, âindividualâ, âteamâ and âotherâ contributing factors, which impacted upon the non-technical skills of medical emergency teams. Conclusion Non-technical skills of hospital medical emergency teams differ, and the impact of the skill mix on resuscitation outcomes was recognised by team members. These findings emphasize the importance non-technical skills in resuscitation training and well-developed processes for medical emergency teams
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