10,225 research outputs found
Orbit and Optics Improvement by Evaluating the Nonlinear BPM Response in CESR
We present an improved system for orbit and betatron phase measurement
utilizing nonlinear models of BPM pickup response. We first describe the
calculation of the BPM pickup signals as nonlinear functions of beam position
using Green's reciprocity theorem with a two-dimensional formalism. We then
describe the incorporation of these calculations in our beam position
measurements by inverting the nonlinear functions, giving us beam position as a
function of the pickup signals, and how this is also used to improve our
measurement of the betatron phase advance. Measurements are presented comparing
this system with the linearized pickup response used historically at CESR.Comment: 7 pages, 11 figure
Semiclassical theory of the interaction correction to the conductance of antidot arrays
Electron-electron interactions are responsible for a correction to the
conductance of a diffusive metal, the "Altshuler-Aronov correction" . Here we study the counterpart of this correction for a ballistic
conductor, in which the electron motion is governed by chaotic classical
dynamics. In the ballistic conductance, the Ehrenfest time enters as
an additional time scale that determines the magnitude of quantum interference
effects. The Ehrenfest time effectively poses a short-time threshold for the
trajectories contributing to the interaction correction. As a consequence,
becomes exponentially suppressed if the Ehrenfest time is
larger than the dwell time or the inverse temperature. We discuss the explicit
dependence on Ehrenfest time in quasi-one and two-dimensional antidot arrays.
For strong interactions, the sign of may change as a function
of temperature for temperatures in the vicinity of .Comment: 20 pages, 10 figures, published versio
A parabolic free boundary problem with Bernoulli type condition on the free boundary
Consider the parabolic free boundary problem For a
realistic class of solutions, containing for example {\em all} limits of the
singular perturbation problem we prove that one-sided
flatness of the free boundary implies regularity.
In particular, we show that the topological free boundary
can be decomposed into an {\em open} regular set (relative to
) which is locally a surface with H\"older-continuous space
normal, and a closed singular set.
Our result extends the main theorem in the paper by H.W. Alt-L.A. Caffarelli
(1981) to more general solutions as well as the time-dependent case. Our proof
uses methods developed in H.W. Alt-L.A. Caffarelli (1981), however we replace
the core of that paper, which relies on non-positive mean curvature at singular
points, by an argument based on scaling discrepancies, which promises to be
applicable to more general free boundary or free discontinuity problems
Uses of a small field value which falls from a metastable maximum over cosmological times
We consider a small, metastable maximum vacuum expectation value of
order of a few eV, for a pseudoscalar Goldstone-like field, which is related to
the scalar inflaton field in an idealized model of a cosmological,
spontaneously-broken chiral symmetry. The b field allows for relating
semi-quantitatively three distinct quantities in a cosmological context.
(1) A very small, residual vacuum energy density or effective cosmological
constant of ~ lambda b_0^4 ~ 2.7 x 10^{-47}GeV^4, for lambda ~ 3 x 10^{-14},
the same as an empirical inflaton self-coupling.
(2) A tiny neutrino mass, less then b_0.
(3) A possible small variation downward of the proton to electron mass ratio
over cosmological time. The latter arises from the motion downward of the
field over cosmological time, toward a nonzero limiting value as . Such behavior is consistent with an equation of motion.
We argue that hypothetical b quanta, potentially inducing new long-range
forces, are absent, because of negative, effective squared mass in an equation
of motion for -field fluctuations.Comment: version accepted for publication in Mod.Phys.Lett.
The news model of asset price determination: An empirical examination of the Danish football club Brøndby IF
According to the news model of asset price determination, only the unexpected component of an information should drive the stock price. We use the Danish publicly listed football club Brøndby IF to analyze how match outcome impacts the stock price. To disentangle gross news from net news, betting odd information is used to control for the expected match outcome. --news model,football industry,betting odds,stock market,market efficiency,event study
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