9,650 research outputs found
Inelastic neutron and x-ray scattering as probes of the sign structure of the Fe-pnictide superconducting gap
Neutron spin-flip scattering observations of a resonance in the
superconducting state is often taken as evidence of an unconventional
superconducting state in which the gap changes sign
for momentum transfers which play an important role in the pairing.
Recently questions regarding this identification for the Fe-pnictide
superconductors have been raised and it has been suggested that
. Here we propose that inelastic neutron or x-ray
scattering measurements of the spectral weight of a phonon of momentum can
distinguish between these two pairing scenarios.Comment: 4 pages, 4 figure
Photonic Anomalous Quantum Hall Effect
We experimentally realize a photonic analogue of the anomalous quantum Hall
insulator using a two-dimensional (2D) array of coupled ring resonators.
Similar to the Haldane model, our 2D array is translation invariant, has zero
net gauge flux threading the lattice, and exploits next-nearest neighbor
couplings to achieve a topologically non-trivial bandgap. Using direct imaging
and on-chip transmission measurements, we show that the bandgap hosts
topologically robust edge states. We demonstrate a topological phase transition
to a conventional insulator by frequency detuning the ring resonators and
thereby breaking the inversion symmetry of the lattice. Furthermore, the
clockwise or the counter-clockwise circulation of photons in the ring
resonators constitutes a pseudospin degree of freedom. We show that the two
pseudospins acquire opposite hopping phases and their respective edge states
propagate in opposite directions. These results are promising for the
development of robust reconfigurable integrated nanophotonic devices for
applications in classical and quantum information processing
Limit distributions for the maxima of stationary Gaussian processes
AbstractLet {Xn} be a stationary Gaussian sequence with E{X0} = 0, {X20} = 1 and E{X0Xn} = rn n Let cn = (2ln n)built12, bn = cnā 12c-1n ln(4Ļ ln n), and set Mn = max0 ā©½kā©½nXk. A classical result for independent normal random variables is that P[cn(Mnābn)ā©½x]āexp[-e-x] as n ā ā for all x. Berman has shown that (1) applies as well to dependent sequences provided rnlnn = o(1). Suppose now that {rn} is a convex correlation sequence satisfying rn = o(1), (rnlnn)-1 is monotone for large n and o(1). Then P[rn-12(Mn ā (1ārn)12bn)ā©½x] ā Š¤(x) for all x, where Š¤ is the normal distribution function. While the normal can thus be viewed as a second natural limit distribution for {Mn}, there are others. In particular, the limit distribution is given below when rn is (sufficiently close to) Ī³/ln n. We further exhibit a collection of limit distributions which can arise when rn decays to zero in a nonsmooth manner. Continuous parameter Gaussian processes are also considered. A modified version of (1) has been given by Pickands for some continuous processes which possess sufficient asymptotic independence properties. Under a weaker form of asymptotic independence, we obtain a version of (2)
Generating Explanatory Captions for Information Graphics
Graphical presentations can be used to communicate information in relational data sets succinctly and effectively. However, novel graphical presentations about numerous attributes and their relationships are often difficult to understand completely until explained. Automatically generated graphical presentations must therefore either be limited to simple, conventional ones, or risk incomprehensibility. One way of alleviating this problem is to design graphical presentation systems that can work in conjunction with a natural language generator to produce "explanatory captions." This paper presents three strategies for generating explanatory captions to accompany information graphics based on: (1) a representation of the structure of the graphical presentation (2) a framework for identifyingthe perceptual complexity of graphical elements, and (3) the structure of the data expressed in the graphic. We describe an implemented system and illustrate how it is used to generate explanatory cap..
Using Available Volume to Predict Fluid Diffusivity in Random Media
We propose a simple equation for predicting self-diffusivity of fluids
embedded in random matrices of identical, but dynamically frozen, particles
(i.e., quenched-annealed systems). The only nontrivial input is the volume
available to mobile particles, which also can be predicted for two common
matrix types that reflect equilibrium and non-equilibrium fluid structures. The
proposed equation can account for the large differences in mobility exhibited
by quenched-annealed systems with indistinguishable static pair correlations,
illustrating the key role that available volume plays in transport.Comment: to appear in Physical Review E (12 pages, 4 figures
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