9,659 research outputs found
Vortex-boson duality in four space-time dimensions
A continuum version of the vortex-boson duality in (3+1) dimensions is
formulated and its implications studied in the context of a pair Wigner crystal
in underdoped cuprate superconductors. The dual theory to a phase fluctuating
superconductor (or superfluid) is shown to be a theory of bosonic strings
interacting through a Kalb-Ramond rank-2 tensorial gauge field. String
condensation produces Higgs mass for the gauge field and the expected Wigner
crystal emerges as an interesting space-time analog of the Abrikosov lattice.Comment: 4 pages REVTeX; for related work and info visit
http://www.physics.ubc.ca/~fran
On the Tail of the Overlap Probability Distribution in the Sherrington--Kirkpatrick Model
We investigate the large deviation behavior of the overlap probability
density in the Sherrington--Kirkpatrick model from several analytical
perspectives. First we analyze the spin glass phase using the coupled replica
scheme. Here generically
, and we compute the first correction to the expansion of \A
in powers of . We study also the case, where is know
exactly. Finally we study the paramagnetic phase, where exact results valid for
all 's are obtained. The overall agreement between the various points of
view is very satisfactory. Data from large scale numerical simulations show
that the predicted behavior can be detected already on moderate lattice sizes.Comment: 18 pages including ps figure
Levinson theorem for Aharonov-Bohm scattering in two dimensions
We apply the recently generalized Levinson theorem for potentials with
inverse square singularities [Sheka et al, Phys.Rev.A, v.68, 012707 (2003)] to
Aharonov-Bohm systems in two-dimensions. By this theorem, the number of bound
states in a given m-th partial wave is related to the phase shift and the
magnetic flux. The results are applied to 2D soliton-magnon scattering.Comment: 5 pages (REVTeX
A Study of a Mini-drift GEM Tracking Detector
A GEM tracking detector with an extended drift region has been studied as
part of an effort to develop new tracking detectors for future experiments at
RHIC and for the Electron Ion Collider that is being planned for BNL or JLAB.
The detector consists of a triple GEM stack with a small drift region that was
operated in a mini TPC type configuration. Both the position and arrival time
of the charge deposited in the drift region were measured on the readout plane
which allowed the reconstruction of a short vector for the track traversing the
chamber. The resulting position and angle information from the vector could
then be used to improve the position resolution of the detector for larger
angle tracks, which deteriorates rapidly with increasing angle for conventional
GEM tracking detectors using only charge centroid information. Two types of
readout planes were studied. One was a COMPASS style readout plane with 400
micron pitch XY strips and the other consisted of 2x10mm2 chevron pads. The
detector was studied in test beams at Fermilab and CERN, along with additional
measurements in the lab, in order to determine its position and angular
resolution for incident track angles up to 45 degrees. Several algorithms were
studied for reconstructing the vector using the position and timing information
in order to optimize the position and angular resolution of the detector for
the different readout planes. Applications for large angle tracking detectors
at RHIC and EIC are also discussed.Comment: Submitted to the IEEE Transactions on Nuclear Scienc
Phase coexistence and finite-size scaling in random combinatorial problems
We study an exactly solvable version of the famous random Boolean
satisfiability problem, the so called random XOR-SAT problem. Rare events are
shown to affect the combinatorial ``phase diagram'' leading to a coexistence of
solvable and unsolvable instances of the combinatorial problem in a certain
region of the parameters characterizing the model. Such instances differ by a
non-extensive quantity in the ground state energy of the associated diluted
spin-glass model. We also show that the critical exponent , controlling
the size of the critical window where the probability of having solutions
vanishes, depends on the model parameters, shedding light on the link between
random hyper-graph topology and universality classes. In the case of random
satisfiability, a similar behavior was conjectured to be connected to the onset
of computational intractability.Comment: 10 pages, 5 figures, to appear in J. Phys. A. v2: link to the XOR-SAT
probelm adde
Nonequilibrium dynamics of a simple stochastic model
We investigate the low-temperature dynamics of a simple stochastic model,
introduced recently in the context of the physics of glasses. The slowest
characteristic time at equilibrium diverges exponentially at low temperature.
On smaller time scales, the nonequilibrium dynamics of the system exhibits an
aging regime. We present an analytical study of the scaling behaviour of the
mean energy, of its local correlation and response functions, and of the
associated fluctuation-dissipation ratio throughout the regime of low
temperature and long times. This analysis includes the aging regime, the
convergence to equilibrium, and the crossover behaviour between them.Comment: 36 pages, plain tex, 7 figures, to be published by Journal of Physics
Dirac quasiparticles in the mixed state
Energies and wave functions are calculated for d-wave quasiparticles in the
mixed state using the formalism of Franz and Tesanovic for the low-lying energy
levels. The accuracy of the plane-wave expansion is explored by comparing
approximate to exact results for a simplified one-dimensional problem, and the
convergence of the plane- wave expansion to the two-dimensional case is
studied. The results are used to calculate the low-energy tunneling density of
states and the low-temperature specific heat, and these theoretical results are
compared to semiclassical treatments and to the available data. Implications
for the muon spin resonance measurements of vortex core size are also
discussed.Comment: 13 pages, 15 figures, RevTeX. References corrected. A factor of 2 in
the results has been corrected, and the conclusions have been update
A W:B4C multilayer phase retarder for broadband polarization analysis of soft x-ray radiation \ud
A W:B4C multilayer phase retarder has been designed and characterized which shows a nearly constant phase retardance between 640 and 850 eV photon energies when operated near the Bragg condition. This freestanding transmission multilayer was used successfully to determine, for the first time, the full polarization vector at soft x-ray energies above 600 eV, which was not possible before due to the lack of suitable optical elements. Thus, quantitative polarimetry is now possible at the 2p edges of the magnetic substances Fe, Co, and Ni for the benefit of magnetic circular dichroism spectroscopy employing circularly polarized synchrotron radiatio
Controlled vortex core switching in a magnetic nanodisk by a rotating field
The switching process of the vortex core in a Permalloy nanodisk affected by
a rotating magnetic field is studied theoretically. A detailed description of
magnetization dynamics is obtained by micromagnetic simulations.Comment: REVTeX, 5 pages, 5 figure
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