20,687 research outputs found
Work in Progress: Do Women Score Lower Than Men on Computer Engineering Exams?
Women have long been underrepresented in undergraduate engineering programs. Women may drop out of engineering programs when they become discouraged by low exam scores. In this project, we examine whether women earn lower exam scores than men and whether Dweck's model of self-theories explains the difference. Dweck proposed two categories
for individuals beliefs about intelligence: incremental theories and entity theories. Dweck found that women are more likely to be entity
theorists than men. In our study, we found that the difference between exam averages between women and men, and between entity and incremental theorists were not statistically significant.published or submitted for publicationis peer reviewe
Traveling Dark Solitons in Superfluid Fermi Gases
Families of dark solitons exist in superfluid Fermi gases. The
energy-velocity dispersion and number of depleted particles completely
determines the dynamics of dark solitons on a slowly-varying background
density. For the unitary Fermi gas we determine these relations from general
scaling arguments and conservation of local particle number. We find solitons
to oscillate sinusoidally at the trap frequency reduced by a factor of
. Numerical integration of the time-dependent Bogoliubov-de Gennes
equation determines spatial profiles and soliton dispersion relations across
the BEC-BCS crossover and proves consistent with the scaling relations at
unitarity.Comment: Small changes in response to referee's comments; fig 1 revised and
refs updated. Cross listed to nucl-th due to interest in the unitary Fermi
ga
Pairing in Asymmetrical Fermi Systems with Intra- and Inter-Species Correlations
We consider inter- and intra-species pairing interactions in an asymmetrical
Fermi system. Using equation of motion method, we obtain coupled mean-field
equations for superfluid gap functions and population densities. We construct a
phase diagram across BCS-BEC regimes. Due to intra-species correlations, the
BCS singlet superfluid state can sustain finite polarizations, . For larger
, we find phase separations in BCS and BEC regimes. A superfluid phase
exists for all deep in BEC regime. Our results may apply to pairing in
ultracold fermions, nuclear and quark matter physics.Comment: Contents revised. Added reference
Response to Comment on "Pairing and Phase Separation in a Polarized Fermi Gas"
Zwierlein and Ketterle rely on subjective arguments and fail to recognize
important differences in physical parameters between our experiment and theirs.
We stand by the conclusions of our original report
On the Connection Between Momentum Cutoff and Operator Cutoff Regularizations
Operator cutoff regularization based on the original Schwinger's proper-time
formalism is examined. By constructing a regulating smearing function for the
proper-time integration, we show how this regularization scheme simulates the
usual momentum cutoff prescription yet preserves gauge symmetry even in the
presence of the cutoff scales. Similarity between the operator cutoff
regularization and the method of higher (covariant) derivatives is also
observed. The invariant nature of the operator cutoff regularization makes it a
promising tool for exploring the renormalization group flow of gauge theories
in the spirit of Wilson-Kadanoff blocking transformation.Comment: 28 pages in plain TeX, no figures. revised and expande
High-order localized spoof surface plasmon resonances and experimental verifications
We theoretically demonstrated and experimentally verified high-order radial
spoof localized surface plasmon resonances supported by textured metal
particles. Through an effective medium theory and exact numerical simulations,
we show the emergence of these geometrically-originated electromagnetic modes
at microwave frequencies. The occurrence of high-order radial spoof plasmon
resonances is experimentally verified in ultrathin disks. Their spectral and
near-field properties are characterized experimentally, showing an excellent
agreement with theoretical predictions. Our findings shed light into the nature
of spoof localized surface plasmons, and open the way to the design of
broadband plasmonic devices able to operate at very different frequency
regimes.Comment: 29 pages, 10 figure
Spin relaxation in a GaAs quantum dot embedded inside a suspended phonon cavity
The phonon-induced spin relaxation in a two-dimensional quantum dot embedded
inside a semiconductor slab is investigated theoretically. An enhanced
relaxation rate is found due to the phonon van Hove singularities. Oppositely,
a vanishing deformation potential may also result in a suppression of the spin
relaxation rate. For larger quantum dots, the interplay between the spin orbit
interaction and Zeeman levels causes the suppression of the relaxation at
several points. Furthermore, a crossover from confined to bulk-like systems is
obtained by varying the width of the slab.Comment: 5 pages, 4 figures, to apper in Phys. Rev. B (2006
Hole burning in a nanomechanical resonator coupled to a Cooper pair box
We propose a scheme to create holes in the statistical distribution of
excitations of a nanomechanical resonator. It employs a controllable coupling
between this system and a Cooper pair box. The success probability and the
fidelity are calculated and compared with those obtained in the atom-field
system via distinct schemes. As an application we show how to use the
hole-burning scheme to prepare (low excited) Fock states.Comment: 7 pages, 10 figure
Dynamical symmetry breaking as the origin of the zero--resistance state in an -driven system
Under a strong drive the zero-frequency linear response dissipative
resistivity of a homogeneous state is allowed to become
negative. We show that such a state is absolutely unstable. The only
time-independent state of a system with a is characterized by
a current which almost everywhere has a magnitude fixed by the
condition that the nonlinear dissipative resistivity .
As a result, the dissipative component of the electric field vanishes. The
total current may be varied by rearranging the current pattern appropriately
with the dissipative component of the -electric field remaining zero. This
result, together with the calculation of Durst \emph{et. al.}, indicating the
existence of regimes of applied microwave field and magnetic field
where , explains the zero-resistance state observed by Mani
\emph{et. al.} and Zudov \emph{et. al.}.Comment: Published versio
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