40,817 research outputs found
Variational Formulation for the KPZ and Related Kinetic Equations
We present a variational formulation for the Kardar-Parisi-Zhang (KPZ)
equation that leads to a thermodynamic-like potential for the KPZ as well as
for other related kinetic equations. For the KPZ case, with the knowledge of
such a potential we prove some global shift invariance properties previously
conjectured by other authors. We also show a few results about the form of the
stationary probability distribution function for arbitrary dimensions. The
procedure used for KPZ was extended in order to derive more general forms of
such a functional leading to other nonlinear kinetic equations, as well as
cases with density dependent surface tension.Comment: RevTex, 8pgs, double colum
Energy-level pinning and the 0.7 spin state in one dimension: GaAs quantum wires studied using finite-bias spectroscopy
We study the effects of electron-electron interactions on the energy levels
of GaAs quantum wires (QWs) using finite-bias spectroscopy. We probe the energy
spectrum at zero magnetic field, and at crossings of opposite-spin-levels in
high in-plane magnetic field B. Our results constitute direct evidence that
spin-up (higher energy) levels pin to the chemical potential as they populate.
We also show that spin-up and spin-down levels abruptly rearrange at the
crossing in a manner resembling the magnetic phase transitions predicted to
occur at crossings of Landau levels. This rearranging and pinning of subbands
provides a phenomenological explanation for the 0.7 structure, a
one-dimensional (1D) nanomagnetic state, and its high-B variants.Comment: 6 pages, 4 figure
Kaluza-Klein Dark Matter and the Positron Excess
The excess of cosmic positrons observed by the HEAT experiment may be the
result of Kaluza-Klein dark matter annihilating in the galactic halo.
Kaluza-Klein dark matter annihilates dominantly into charged leptons that yield
a large number and hard spectrum of positrons per annihilation. Given a
Kaluza-Klein dark matter particle with a mass in the range of 300-400 GeV, no
exceptional substructure or clumping is needed in the local distribution of
dark matter to generate a positron flux that explains the HEAT observations.
This is in contrast to supersymmetric dark matter that requires unnaturally
large amounts of dark substructure to produce the observed positron excess.
Future astrophysical and collider tests are outlined that will confirm or rule
out this explanation of the HEAT data.Comment: 5 pages, 3 figures, REVTeX
Quantum states on supersymmetric minisuperspace with a cosmological constant
Spatially homogeneous models in quantum supergravity with a nonvanishing
cosmological constant are studied. A class of exact nontrivial solutions of the
supersymmetry and Lorentz constraints is obtained in terms of the Chern-Simons
action on the spatially homogeneous 3-manifold, both in Ashketar variables
where the solution is explicit up to reality conditions, and, more concretely,
in the tetrad-representation, where the solutions are given as integral
representations differing only by the contours of integration. In the limit of
a vanishing cosmological constant earlier exact solutions for Bianchi type IX
models in the tetrad-representation are recovered and additional asymmetric
solutions are found.Comment: 14 pages, late
Disorder-Induced Shift of Condensation Temperature for Dilute Trapped Bose Gases
We determine the leading shift of the Bose-Einstein condensation temperature
for an ultracold dilute atomic gas in a harmonic trap due to weak disorder by
treating both a Gaussian and a Lorentzian spatial correlation for the quenched
disorder potential. Increasing the correlation length from values much smaller
than the geometric mean of the trap scale and the mean particle distance to
much larger values leads first to an increase of the positive shift to a
maximum at this critical length scale and then to a decrease.Comment: Author information under
http://www.theo-phys.uni-essen.de/tp/ags/pelster_di
Systematic derivation of a rotationally covariant extension of the 2-dimensional Newell-Whitehead-Segel equation
An extension of the Newell-Whitehead-Segel amplitude equation covariant under
abritrary rotations is derived systematically by the renormalization group
method.Comment: 8 pages, to appear in Phys. Rev. Letters, March 18, 199
Predicting sexual problems in women: The relevance of sexual excitation and sexual inhibition
This is the post-print version of the article. The official published version can be obtained from the link below.Data from a non-clinical sample of 540 heterosexual women were used to examine the relationships between scores on the Sexual Excitation/Sexual Inhibition Inventory for Women (SESII-W) and ratings of current sexual problems, lifetime arousal difficulty, lifetime orgasm difficulty, and lifetime problems with low sexual interest. Multiple regression analyses also included several demographic/background variables as predictors: age, full-time employment, completed college, children in household, married, health ratings, importance of sex, and whether the woman was in a sexual relationship. The strongest statistical predictors of both current and lifetime sexual problems were the SESII-W inhibition factors Arousal Contingency and Concerns about Sexual Function. Demographic factors did not feature largely in any of the models predicting sexual problems even when statistically significant relationships were found. If future research supports the predictive utility of the SESII-W in identifying women who are more likely to experience sexual difficulties, these scales may be used as prognostic factors in treatment studies.This study was funded, in part, by a grant from the Lilly Centre for Women's Health
Conceptualisations of childrenâs wellbeing at school: the contribution of recognition theory
A large study in Australian schools aimed to elucidate understandings of âwellbeingâ and of factors in school life that contribute to it. Students and teachers understood wellbeing primarily, and holistically, in terms of interpersonal relationships, in contrast to policy documents which mainly focused on âproblem areasâ such as mental health. The study also drew on recognition theory as developed by the social philosopher Axel Honneth. Results indicate that recognition theory may be useful in understanding wellbeing in schools, and that empirical research in schools may give rise to further questions regarding theory
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