1,492,146 research outputs found
Renormalization Group Study of the Electron-phonon Interaction in the High Tc Cuprates
We generalize the numerical renormalization group scheme to study the
phonon-mediated retarded interactions in the high Tc cuprates. We find that
three sets of phonon-mediated retarded quasiparticle scatterings grow under RG
flow. These scatterings share the following common features: 1) the initial and
final quasiparticle momenta are in the antinodal regions, and 2) the scattering
amplitudes have a symmetry. All three sets of retarded interaction
are driven to strong coupling by the magnetic fluctuations around .
After growing strong, these retarded interaction will trigger density wave
orders with d-wave symmetry. However, due to the d-wave form factor they will
leave the nodal quasiparticle unaffected. We conclude that the main effect of
electron-phonon coupling in the cuprates is to promote these density wave
orders.Comment: 4 pages, 3 figures, references added, added more details about
others' previous studie
An Array of Spatulate Sensilla on Antennae of Male \u3ci\u3eBrachymeria Lasus\u3c/i\u3e (Hymenoptera: Chalcididae)
An array of spatulate sensilla on the ventral flagellar surface of each antenna of male Brachymeria lasus occurs only on segments IV-VII and is absent on female antennae. Most such sensilla are on segment VI. Each spatulate sensillum was 15 p, by 16.7 p with a stalk extending 17 p, from the antennal base. Pores were not apparent, but the sensillum surface was imbricated. The sensilla are speculated to have a role in the courtship sequence of this chalcid by functioning both as chemoreceptors of the female-produced sex pheromone and as mechanoreceptors to indicate female receptivity, as female B. lasus typically raise the abdomen to expose the genital pocket
Entanglement between an electron and a nuclear spin 1/2
We report on the preparation and detection of entangled states between an
electron spin 1/2 and a nuclear spin 1/2 in a molecular single crystal. These
were created by applying pulses at ESR (9.5 GHz) and NMR (28 MHz) frequencies.
Entanglement was detected by using a special entanglement detector sequence
based on a unitary back transformation including phase rotation.Comment: 4 pages, 3 figure
Anharmonic effects in magnetoelastic chains
We describe a new mechanism leading to the formation of rational
magnetization plateau phases, which is mainly due to the anharmonic spin-phonon
coupling. This anharmonicity produces plateaux in the magnetization curve at
unexpected values of the magnetization without explicit magnetic frustration in
the Hamiltonian and without an explicit breaking of the translational symmetry.
These plateau phases are accompanied by magneto-elastic deformations which are
not present in the harmonic case.Comment: 5 pages, 3 figure
Dynamics of Learning with Restricted Training Sets I: General Theory
We study the dynamics of supervised learning in layered neural networks, in
the regime where the size of the training set is proportional to the number
of inputs. Here the local fields are no longer described by Gaussian
probability distributions and the learning dynamics is of a spin-glass nature,
with the composition of the training set playing the role of quenched disorder.
We show how dynamical replica theory can be used to predict the evolution of
macroscopic observables, including the two relevant performance measures
(training error and generalization error), incorporating the old formalism
developed for complete training sets in the limit as a
special case. For simplicity we restrict ourselves in this paper to
single-layer networks and realizable tasks.Comment: 39 pages, LaTe
Environmental stability graphite/PMR-15 composites
During the past few years the Boeing Company was screening graphite composites for use in hot areas of engine nacelle structure. Structural and thermal analyses have shown that there is the potential for a 25 to 30 percent weight savings by using a graphite polyimide (Gr/PI) composite material in this type of structure. Work conducted on the NASA CASTS program (Composites for Advanced Space Transportation Systems) amply demonstrated the capability of Graphite/PMR-15 for short term service (125 hours) at temperatures up to 589 K (600 F). In addition, the CASTS program demonstrated that large structures could be fabricated using Gr/PMR-15. In commercial applications, however, the requirement exists for long term service capability (tens of thousands of hours) at temperatures ranging upwards from 449 K (350 F). The results of Graphite/PMR-15 materials characterization efforts conducted at Boeing are presented with emphasis on materials properties after isothermal aging at temperatures of 449 K (350 F) and above
Enhanced Higgs boson production and avoidance of CP-violation and FCNC in the MPP inspired 2HDM
The multiple point principle (MPP) can be used to suppress non--diagonal
flavour transitions and CP violation in the two Higgs doublet extension of the
standard model. We discuss the quasi--fixed point scenario in the MPP inspired
two Higgs doublet model which leads to the enhanced production of Higgs
particles at the LHC if the MPP scale is low.Comment: Talk given at the 2007 Europhysics Conference on High Energy Physics,
Manchester, England, 19-25 July 2007, CERN preprint number added, references
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