107,893 research outputs found
Hyperspherical Close-Coupling Calculation of D-wave Positronium Formation and Excitation Cross Sections in Positron-Hydrogen Scattering
Hyperspherical close-coupling method is used to calculate the elastic,
positronium formation and excitation cross sections for positron collisions
with atomic hydrogen at energies below the H(n=4) threshold for the J=2 partial
wave. The resonances below each inelastic threshold are also analyzed. The
adiabatic hyperspherical potential curves are used to identify the nature of
these resonances.Comment: 12 pages(in a TeX file) +8 Postscript figure
Globally Optimal Crowdsourcing Quality Management
We study crowdsourcing quality management, that is, given worker responses to
a set of tasks, our goal is to jointly estimate the true answers for the tasks,
as well as the quality of the workers. Prior work on this problem relies
primarily on applying Expectation-Maximization (EM) on the underlying maximum
likelihood problem to estimate true answers as well as worker quality.
Unfortunately, EM only provides a locally optimal solution rather than a
globally optimal one. Other solutions to the problem (that do not leverage EM)
fail to provide global optimality guarantees as well. In this paper, we focus
on filtering, where tasks require the evaluation of a yes/no predicate, and
rating, where tasks elicit integer scores from a finite domain. We design
algorithms for finding the global optimal estimates of correct task answers and
worker quality for the underlying maximum likelihood problem, and characterize
the complexity of these algorithms. Our algorithms conceptually consider all
mappings from tasks to true answers (typically a very large number), leveraging
two key ideas to reduce, by several orders of magnitude, the number of mappings
under consideration, while preserving optimality. We also demonstrate that
these algorithms often find more accurate estimates than EM-based algorithms.
This paper makes an important contribution towards understanding the inherent
complexity of globally optimal crowdsourcing quality management
Sequence-Dependent Effects on the Properties of Semiflexible Biopolymers
Using path integral technique, we show exactly that for a semiflexible
biopolymer in constant extension ensemble, no matter how long the polymer and
how large the external force, the effects of short range correlations in the
sequence-dependent spontaneous curvatures and torsions can be incorporated into
a model with well-defined mean spontaneous curvature and torsion as well as a
renormalized persistence length. Moreover, for a long biopolymer with large
mean persistence length, the sequence-dependent persistence lengths can be
replaced by their mean. However, for a short biopolymer or for a biopolymer
with small persistence lengths, inhomogeneity in persistence lengths tends to
make physical observables very sensitive to details and therefore less
predictable
Fast entanglement of two charge-phase qubits through nonadiabatic coupling to a large junction
We propose a theoretical protocol for quantum logic gates between two
Josephson junction charge-phase qubits through the control of their coupling to
a large junction. In the low excitation limit of the large junction when
, it behaves effectively as a quantum data-bus mode of a
harmonic oscillator. Our protocol is efficient and fast. In addition, it does
not require the data-bus to stay adiabatically in its ground state, as such it
can be implemented over a wide parameter regime independent of the data-bus
quantum state.Comment: 5 pages, 1 figur
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