26,293 research outputs found
Systematics of the Relationship between Vacuum Energy Calculations and Heat Kernel Coefficients
Casimir energy is a nonlocal effect; its magnitude cannot be deduced from
heat kernel expansions, even those including the integrated boundary terms. On
the other hand, it is known that the divergent terms in the regularized (but
not yet renormalized) total vacuum energy are associated with the heat kernel
coefficients. Here a recent study of the relations among the eigenvalue
density, the heat kernel, and the integral kernel of the operator
is exploited to characterize this association completely.
Various previously isolated observations about the structure of the regularized
energy emerge naturally. For over 20 years controversies have persisted
stemming from the fact that certain (presumably physically meaningful) terms in
the renormalized vacuum energy density in the interior of a cavity become
singular at the boundary and correlate to certain divergent terms in the
regularized total energy. The point of view of the present paper promises to
help resolve these issues.Comment: 19 pages, RevTeX; Discussion section rewritten in response to
referees' comments, references added, minor typos correcte
Correlations around an interface
We compute one-loop correlation functions for the fluctuations of an
interface using a field theory model. We obtain them from Feynman diagrams
drawn with a propagator which is the inverse of the Hamiltonian of a
Poschl-Teller problem. We derive an expression for the propagator in terms of
elementary functions, show that it corresponds to the usual spectral sum, and
use it to calculate quantities such as the surface tension and interface
profile in two and three spatial dimensions. The three-dimensional quantities
are rederived in a simple, unified manner, whereas those in two dimensions
extend the existing literature, and are applicable to thin films. In addition,
we compute the one-loop self-energy, which may be extracted from experiment, or
from Monte Carlo simulations. Our results may be applied in various scenarios,
which include fluctuations around topological defects in cosmology,
supersymmetric domain walls, Z(N) bubbles in QCD, domain walls in magnetic
systems, interfaces separating Bose-Einstein condensates, and interfaces in
binary liquid mixtures.Comment: RevTeX, 13 pages, 6 figure
Geothermal Casimir Phenomena
We present first worldline analytical and numerical results for the
nontrivial interplay between geometry and temperature dependencies of the
Casimir effect. We show that the temperature dependence of the Casimir force
can be significantly larger for open geometries (e.g., perpendicular plates)
than for closed geometries (e.g., parallel plates). For surface separations in
the experimentally relevant range, the thermal correction for the
perpendicular-plates configuration exhibits a stronger parameter dependence and
exceeds that for parallel plates by an order of magnitude at room temperature.
This effect can be attributed to the fact that the fluctuation spectrum for
closed geometries is gapped, inhibiting the thermal excitation of modes at low
temperatures. By contrast, open geometries support a thermal excitation of the
low-lying modes in the gapless spectrum already at low temperatures.Comment: 8 pages, 3 figures, contribution to QFEXT07 proceedings, v2:
discussion switched from Casimir energy to Casimir force, new analytical
results included, matches JPhysA versio
Trends in U.S. Public Awareness of Racial and Ethnic Health Disparities (1999-2010): Study Brief
None provided
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
Emergence of Oscillons in an Expanding Background
We consider a (1+1) dimensional scalar field theory that supports oscillons,
which are localized, oscillatory, stable solutions to nonlinear equations of
motion. We study this theory in an expanding background and show that oscillons
now lose energy, but at a rate that is exponentially small when the expansion
rate is slow. We also show numerically that a universe that starts with
(almost) thermal initial conditions will cool to a final state where a
significant fraction of the energy of the universe -- on the order of 50% -- is
stored in oscillons. If this phenomenon persists in realistic models, oscillons
may have cosmological consequences.Comment: 13 pages, 4 .eps figures, uses RevTeX4; v2: clarified details of
expansion, added reference
Fronts and interfaces in bistable extended mappings
We study the interfaces' time evolution in one-dimensional bistable extended
dynamical systems with discrete time. The dynamics is governed by the
competition between a local piece-wise affine bistable mapping and any
couplings given by the convolution with a function of bounded variation. We
prove the existence of travelling wave interfaces, namely fronts, and the
uniqueness of the corresponding selected velocity and shape. This selected
velocity is shown to be the propagating velocity for any interface, to depend
continuously on the couplings and to increase with the symmetry parameter of
the local nonlinearity. We apply the results to several examples including
discrete and continuous couplings, and the planar fronts' dynamics in
multi-dimensional Coupled Map Lattices. We eventually emphasize on the
extension to other kinds of fronts and to a more general class of bistable
extended mappings for which the couplings are allowed to be nonlinear and the
local map to be smooth.Comment: 27 pages, 3 figures, submitted to Nonlinearit
A Meta-Analytic Review of Achievement Goal Orientation Correlates in Competitive Sport: A Follow-Up to Lochbaum et al. (2016)
Recent quantitative research in competitive sport with the Task and Ego Orientations in Sport Questionnaire (TEOSQ) and Perceptions of Success Questionnaire (POSQ) pointed to a potential critical issue that the two questionnaires did not agree across a number tested hypotheses (Lochbaum, Kazak Çetinkalp, Graham, Wright, & Zazo, 2016). Thus, the present quantitative review examined whether correlates of the two achievement goal orientations were moderated by the two measures. To achieve this purpose, 772 unique correlates (489 TEOSQ, 283 POSQ; 402 task orientation, 370 ego orientation) from 93 studies spanning 1989-2016 from 32 countries with 26,387 participants were placed into 15 different categories and meta-analyzed. The task goal orientation was significantly and small to moderate in meaningfulness related to adaptive success factors (rw=.29), maladaptive success factors (rw=-.12), desirable behaviors (rw=.28), positive emotions (rw=.35), amotivation (rw=-.13), extrinsic motivation (rw=.20), external regulations (rw=.12), internal regulations (rw=.34), intrinsic motivation (rw=.47), the mastery/task climate (rw=.38), perceived competence (rw=.26), and trait selfesteem (rw=.35). The ego goal orientation was significantly and small in meaningfulness related to adaptive success factors (rw=.10), maladaptive success factors (rw=.12), negative emotions (rw=.11), undesirable behaviors (rw=.23), amotivation (rw=.16), extrinsic motivation (rw=.28), external regulation (rw=.21), intrinsic motivation (rw=.14), performance/ego climate (rw=.28), and perceived competence (rw=.17). The questionnaire measure was a significant moderator for the task goal orientation relationship with desirable behaviors (POSQ rw=.24; TEOSQ rw=.37), internal regulations (POSQ rw=.26; TEOSQ rw=.39), and trait self-esteem (POSQ rw=.45; TEOSQ rw=.32) and for the ego goal orientation relationship with performance/ego climate (POSQ rw=.34; TEOSQ rw=.24). Overall, the extent of the questionnaire type being a concern when examining correlates was fortunately minimal. Yet, differences in the two dominant measures exit. Recommendations for future research examining both the TEOSQ and POSQ were proposed
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