16,472 research outputs found
Nature of Quasielectrons and the Continuum of Neutral Bulk Excitations in the Laughlin Quantum Hall Fluids
We construct model wavefunctions for a family of single-quasielectron states
supported by the fractional quantum Hall (FQH) fluid. The charge
= quasielectron state is identified as a composite of a
charge- quasiparticle and a quasihole, orbiting around their
common center of charge with relative angular momentum , and
corresponds precisely to the "composite fermion" construction based on a filled
Landau level plus an extra particle in level . An effective
three-body model (one quasiparticle and two quasiholes) is
introduced to capture the essential physics of the neutral bulk excitations.Comment: 4 pages, 3 figs, minor modifications for the published versio
A novel implementation of method of optimality criterion in synthesizing spacecraft structures with natural frequency constraints
In the design of spacecraft structures, fine tuning the structure to achieve minimum weight with natural frequency constraints is a time consuming process. Here, a novel implementation of the method of optimality criterion (OC) is developed. In this new implementation of OC, the free vibration analysis results are used to compute the eigenvalue sensitivity data required for the formulation. Specifically, the modal elemental strain and kinetic energies are used. Additionally, normalized design parameters are introduced as a second level linking that allows design variables of different values to be linked together. With the use of this novel formulation, synthesis of structures with natural frequency constraint can be carried out manually using modal analysis results. Design examples are presented to illustrate this novel implementation of the optimality criterion method
Analytic description of atomic interaction at ultracold temperatures II: Scattering around a magnetic Feshbach resonance
Starting from a multichannel quantum-defect theory, we derive analytic
descriptions of a magnetic Feshbach resonance in an arbitrary partial wave ,
and the atomic interactions around it. An analytic formula, applicable to both
broad and narrow resonances of arbitrary , is presented for ultracold atomic
scattering around a Feshbach resonance. Other related issues addressed include
(a) the parametrization of a magnetic Feshbach resonance of arbitrary , (b)
rigorous definitions of "broad" and "narrow" resonances of arbitrary and
their different scattering characteristics, and (c) the tuning of the effective
range and the generalized effective range by a magnetic field.Comment: 13 pages, 4 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
D^0-D^0bar mixing in \Upsilon(1S) \to D^0 D^0bar decay at Super-B
\Dz-\Dzb mixing and significant CP violation in the charm system may
indicate the signature of new physics. In this study, we suggest that the
coherent \DzDzb events from the decay of \Upsilon(1S) \to \Dz \Dzb can be
used to measure both mixing parameters and CP violation in charm decays. The
neutral mesons from decay are strongly boosted, so that it
will offer the possibility to measure the proper-time interval, ,
between the fully-reconstructed \Dz and \Dzb. Both coherent and
time-dependent information can be used to extract \Dz-\Dzb mixing parameters.
The sensitivity of the measurement should be improved at B factories or
super-B.Comment: 6 pages, 1 figure, this is the last version to appear in Phys. Rev.
Universal model for exoergic bimolecular reactions and inelastic processes
From a rigorous multichannel quantum-defect formulation of bimolecular
processes, we derive a fully quantal and analytic model for the total rate of
exoergic bimolecular reactions and/or inelastic processes that is applicable
over a wide range of temperatures including the ultracold regime. The theory
establishes a connection between the ultracold chemistry and the regular
chemistry by showing that the same theory that gives the quantum threshold
behavior agrees with the classical Gorin model at higher temperatures. In
between, it predicts that the rates for identical bosonic molecules and
distinguishable molecules would first decrease with temperature outside of the
Wigner threshold region, before rising after a minimum is reached.Comment: 5 pages, 1 figur
Unitarity Cuts with Massive Propagators and Algebraic Expressions for Coefficients
In the first part of this paper, we extend the d-dimensional unitarity cut
method of hep-ph/0609191 to cases with massive propagators. We present formulas
for integral reduction with which one can obtain coefficients of all pentagon,
box, triangle and massive bubble integrals. In the second part of this paper,
we present a detailed study of the phase space integration for unitarity cuts.
We carry out spinor integration in generality and give algebraic expressions
for coefficients, intended for automated evaluation.Comment: 33 pages. v2: notation modified. v3: typos fixe
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