41,713 research outputs found
Majorana Fermion Induced Resonant Andreev Reflection
We describe experimental signatures of Majorana fermion edge states, which
form at the interface between a superconductor and the surface of a topological
insulator. If a lead couples to the Majorana fermions through electron
tunneling, the Majorana fermions induce \textit{resonant} Andreev reflections
from the lead to the grounded superconductor. The linear tunneling conductance
is () if there is an even (odd) number of vortices in the
superconductor. Similar resonance occurs for tunneling into the zero mode in
the vortex core. We also study the current and noise of a two-lead device.Comment: 4 pages, 3 figures. Discussion on STM tunneling into the Majorana
zero mode in the vortex core is adde
NEW PARTICLES AND INTERACTIONS
We analyze the manifestations of new matter particles predicted by models of
new physics beyond the Standard Model, at present and future high--energy
colliders. We consider both the production of these new particles and some of
their indirect signatures at and colliders as well as TeV \ee
colliders with their \ee, e \gamma, \gamma \gamma and modes. The
report is arranged into four main sections plus an overview. These sections
will deal separately with exotic and excited fermions, difermions, and new
interactions.Comment: 64 pages, latex, 30 figures (not included). The full *.ps file
including the figures can be obtained via anonymous ftp at
ftp://lpsvsh.lps.umontreal.ca/hep_th/dpf.ps . To appear as a chapter in
"Electroweak Symmetry Breaking and Beyond the Standard Model", edited by T.
Barklow, S. Dawson, H.E. Haber and S. Siegrist, World Scientifi
Supersolid phase in spin dimer XXZ systems under magnetic field
Using quantum Monte Carlo method, we study, under external magnetic fields,
the ground state phase diagram of the two-dimensional spin =1/2 dimer model
with an anisotropic intra-plane antiferromagnetic coupling. With the anisotropy
, a supersolid phase characterized by a non-uniform
bose condensate density that breaks translational symmetry is found. The rich
phase diagram also contains a checkerboard solid and two different types of
superfluid phase formed by and spin triplets, with finite
staggered magnetization in z-axis and in-plane direction, respectively. As we
show, the model can be realized as a consequence of including the next nearest
neighbor coupling among dimers and our results suggest that spin dimer systems
may be an ideal model system to study the supersolid phase.Comment: 4 pages, 5 figure
Selective Equal-Spin Andreev Reflections Induced by Majorana Fermions
In this work, we find that Majorana fermions induce selective equal spin
Andreev reflections (SESARs), in which incoming electrons with certain spin
polarization in the lead are reflected as counter propagating holes with the
same spin. The spin polarization direction of the electrons of this Andreev
reflected channel is selected by the Majorana fermions. Moreover, electrons
with opposite spin polarization are always reflected as electrons with
unchanged spin. As a result, the charge current in the lead is spin-polarized.
Therefore, a topological superconductor which supports Majorana fermions can be
used as a novel device to create fully spin-polarized currents in paramagnetic
leads. We point out that SESARs can also be used to detect Majorana fermions in
topological superconductors.Comment: 5 pages, 3 figures. Comments are welcome. Title changed to match
published versio
Dynamical stability of entanglement between spin ensembles
We study the dynamical stability of the entanglement between the two spin
ensembles in the presence of an environment. For a comparative study, we
consider the two cases: a single spin ensemble, and two ensembles linearly
coupled to a bath, respectively. In both circumstances, we assume the validity
of the Markovian approximation for the bath. We examine the robustness of the
state by means of the growth of the linear entropy which gives a measure of the
purity of the system. We find out macroscopic entangled states of two spin
ensembles can stably exist in a common bath. This result may be very useful to
generate and detect macroscopic entanglement in a common noisy environment and
even a stable macroscopic memory.Comment: 4 pages, 1 figur
Precision measurement with an optical Josephson junction
We study a new type of Josephson device, the so-called "optical Josephson
junction" as proposed in Phys. Rev. Lett. {\bf 95}, 170402 (2005). Two
condensates are optically coupled through a waveguide by a pair of Bragg beams.
This optical Josephson junction is analogous to the usual Josephson junction of
two condensates weakly coupled via tunneling. We discuss the use of this
optical Josephson junction, for making precision measurements.Comment: 6 pages, 1 figur
Reliability and Validity of Ratings of Perceived Exertion in Persons With Multiple Sclerosis
Objective: To test the reliability and validity of using the Borg rating of perceived exertion (RPE) scale (ratings 6e20) in persons with multiple sclerosis (PwMS).
Design: Nonrandomized repeated measures.
Setting: Research laboratory.
Participants: Volunteer sample (N=27) comprised of 16 PwMS (10 women) and 11 age-matched persons without multiple sclerosis (MS) (6 women). Clinical measures included symptomatic fatigue, depression, and MS functional capacity.
Interventions: A submaximal cycling test was performed to estimate maximal capacity. Participants then pedaled for 2 minutes at 50% and 60% of predicted maximal oxygen consumption per unit time (VÌO2), and physiological measures and RPE were obtained (week 1: response protocol). One week later, participants replicated the prescribed VÌO2 using the RPE range from week 1 (week 2: reproduction protocol). VÌO2, heart rate, and respiratory quotient were measured continuously; RPE and workload were measured every minute; and blood lactate and mean arterial pressure were measured after exercise.
Main Outcome Measures: RPE, workload, VÌO2, and heart rate from week 1 to week 2.
Results: PwMS had greater fatigue (P2, and heart rate were similar between groups. Both groups had an intraclass correlation coefficient \u3e.86 for RPE, workload, and VÌO2. The intraclass correlation coefficient was comparatively lower for heart rate for both groups (MS group: .72, non-MS group: .83). RPE was highly correlated with VÌO2(rZ.691, P
Conclusions: Results suggest that RPE can be reliably reproduced, is valid, and may be used in exercise prescription in mildly to moderately impaired PwMS during cycling exercise
Entanglement between atomic condensates in an optical lattice: effects of interaction range
We study the area-dependent entropy and two-site entanglement for two state
Bose-Einstein condensates in a 2D optical lattice. We consider the case where
the array of two component condensates behave like an ensemble of spin-half
particles with the interaction to its nearest neighbors and next nearest
neighbors. We show how the Hamiltonian of their Bose-Einstein condensate
lattice with nearest-neighbor and next-nearest-neighbor interactions can be
mapped into a harmonic lattice. We use this to determine the entropy and
entanglement content of the lattice.Comment: 5 pages, 3 figures, title change
Coherent control of atomic spin currents in a double well
We propose an experimental feasible method for controlling the atomic
currents of a two-component Bose-Einstein condensate in a double well by
applying an external field to the atoms in one of the potential wells. We study
the ground-state properties of the system and show that the directions of spin
currents and net-particle tunneling can be manipulated by adiabatically varying
the coupling strength between the atoms and the field. This system can be used
for studying spin and tunneling phenomena across a wide range of interaction
parameters. In addition, spin-squeezed states can be generated. It is useful
for quantum information processing and quantum metrology.Comment: 6 pages, 7 figures, minor revisio
Regular expressions as violin bowing patterns
String players spend a significant amount of practice time creating and learning bowings. These may be indicated in the music using up-bow and down-bow symbols, but those traditional notations do not capture the complex bowing patterns that are latent within the music. Regular expressions, a mathematical notation for a simple class of formal languages, can describe precisely the bowing patterns that commonly arise in string music. A software tool based on regular expressions enables performers to search for passages that can be handled with similar bowings, and to edit them consistently. A computer-based music editor incorporating bowing patterns has been implemented, using Lilypond to typeset the music. Our approach has been evaluated by using the editor to study ten movements from six violin sonatas by W. A. Mozart. Our experience shows that the editor is successful at finding passages and inserting bowings; that relatively complex patterns occur a number of times; and that the bowings can be inserted automatically and consistently
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