17,529 research outputs found
Casimir experiments showing saturation effects
We address several different Casimir experiments where theory and experiment
disagree. First out is the classical Casimir force measurement between two
metal half spaces; here both in the form of the torsion pendulum experiment by
Lamoreaux and in the form of the Casimir pressure measurement between a gold
sphere and a gold plate as performed by Decca et al.; theory predicts a large
negative thermal correction, absent in the high precision experiments. The
third experiment is the measurement of the Casimir force between a metal plate
and a laser irradiated semiconductor membrane as performed by Chen et al.; the
change in force with laser intensity is larger than predicted by theory. The
fourth experiment is the measurement of the Casimir force between an atom and a
wall in the form of the measurement by Obrecht et al. of the change in
oscillation frequency of a 87 Rb Bose-Einstein condensate trapped to a fused
silica wall; the change is smaller than predicted by theory. We show that
saturation effects can explain the discrepancies between theory and experiment
observed in all these cases.Comment: 10 pages, 11 figure
Competition between Phase Separation and Spin Density Wave or Charge Density Wave Order: Role of Long-Range Interactions
Recent studies of pairing and charge order in materials such as FeSe,
SrTiO, and 2H-NbSe have suggested that momentum dependence of the
electron-phonon coupling plays an important role in their properties. Initial
attempts to study Hamiltonians which either do not include or else truncate the
range of Coulomb repulsion have noted that the resulting spatial non-locality
of the electron-phonon interaction leads to a dominant tendency to phase
separation. Here we present Quantum Monte Carlo results for such models in
which we incorporate both on-site and intersite electron-electron interactions.
We show that these can stabilize phases in which the density is homogeneous and
determine the associated phase boundaries. As a consequence, the physics of
momentum dependent electron-phonon coupling can be determined outside of the
trivial phase separated regime.Comment: 9 pages, 7 figure
QCD Evolution of the Sivers Asymmetry
We study the QCD evolution of the Sivers effect in both semi-inclusive deep
inelastic scattering (SIDIS) and Drell-Yan production (DY). We pay close
attention to the non-perturbative spin-independent Sudakov factor in the
evolution formalism and find a universal form which can describe reasonably
well the experimental data on the transverse momentum distributions in SIDIS,
DY lepton pair and production. With this Sudakov factor at hand, we
perform a global fitting of all the experimental data on the Sivers asymmetry
in SIDIS from HERMES, COMPASS and Jefferson Lab. We then make predictions for
the Sivers asymmetry in DY lepton pair and production that can be compared
to the future experimental measurements to test the sign change of the Sivers
functions between SIDIS and DY processes and constrain the sea quark Sivers
functions.Comment: 17 pages, 13 figures, published version in PR
New perspective on space and time from Lorentz violation
I present a brief review on space and time in different periods of physics,
and then talk on the nature of space and time from physical arguments. I
discuss the ways to test such a new perspective on space and time through
searching for Lorentz violation in some physical processes. I also make an
introduce to a newly proposed theory of Lorentz violation from basic
considerations.Comment: 10 latex pages. Plenary talk at First LeCosPA Symposium: Towards
Ultimate Understanding of the Universe (LeCosPA2012), National Taiwan
University, Taipei, Taiwan, February 6-9, 201
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