431 research outputs found
Negative-Index Metamaterials: Second-Harmonic Generation, Manley-Rowe Relations and Parametric Amplification
Second harmonic generation and optical parametric amplification in
negative-index metamaterials (NIMs) are studied. The opposite directions of the
wave vector and the Poynting vector in NIMs results in a "backward"
phase-matching condition, causing significant changes in the Manley-Rowe
relations and spatial distributions of the coupled field intensities. It is
shown that absorption in NIMs can be compensated by backward optical parametric
amplification. The possibility of distributed-feedback parametric oscillation
with no cavity has been demonstrated. The feasibility of the generation of
entangled pairs of left- and right-handed counter-propagating photons is
discussed.Comment: 7 pages, 6 figure
Degenerating families of dendrograms
Dendrograms used in data analysis are ultrametric spaces, hence objects of
nonarchimedean geometry. It is known that there exist -adic representation
of dendrograms. Completed by a point at infinity, they can be viewed as
subtrees of the Bruhat-Tits tree associated to the -adic projective line.
The implications are that certain moduli spaces known in algebraic geometry are
-adic parameter spaces of (families of) dendrograms, and stochastic
classification can also be handled within this framework. At the end, we
calculate the topology of the hidden part of a dendrogram.Comment: 13 pages, 8 figure
Theorie de Lubin-Tate non-abelienne et representations elliptiques
Harris and Taylor proved that the supercuspidal part of the cohomology of the
Lubin-Tate tower realizes both the local Langlands and Jacquet-Langlands
correspondences, as conjectured by Carayol. Recently, Boyer computed the
remaining part of the cohomology and exhibited two defects : first, the
representations of GL\_d which appear are of a very particular and restrictive
form ; second, the Langlands correspondence is not realized anymore. In this
paper, we study the cohomology complex in a suitable equivariant derived
category, and show how it encodes Langlands correspondance for all elliptic
representations. Then we transfer this result to the Drinfeld tower via an
enhancement of a theorem of Faltings due to Fargues. We deduce that Deligne's
weight-monodromy conjecture is true for varieties uniformized by Drinfeld's
coverings of his symmetric spaces.Comment: 54 page
On a Conjecture of Rapoport and Zink
In their book Rapoport and Zink constructed rigid analytic period spaces
for Fontaine's filtered isocrystals, and period morphisms from PEL
moduli spaces of -divisible groups to some of these period spaces. They
conjectured the existence of an \'etale bijective morphism of
rigid analytic spaces and of a universal local system of -vector spaces on
. For Hodge-Tate weights and we construct in this article an
intrinsic Berkovich open subspace of and the universal local
system on . We conjecture that the rigid-analytic space associated with
is the maximal possible , and that is connected. We give
evidence for these conjectures and we show that for those period spaces
possessing PEL period morphisms, equals the image of the period morphism.
Then our local system is the rational Tate module of the universal
-divisible group and enjoys additional functoriality properties. We show
that only in exceptional cases equals all of and when the
Shimura group is we determine all these cases.Comment: v2: 48 pages; many new results added, v3: final version that will
appear in Inventiones Mathematica
Radiative Corrections to One-Photon Decays of Hydrogenic Ions
Radiative corrections to the decay rate of n=2 states of hydrogenic ions are
calculated. The transitions considered are the M1 decay of the 2s state to the
ground state and the E1(M2) decays of the and states to
the ground state. The radiative corrections start in order , but the method used sums all orders of . The leading
correction for the E1 decays is calculated and compared
with the exact result. The extension of the calculational method to parity
nonconserving transitions in neutral atoms is discussed.Comment: 22 pages, 2 figure
Excess Spin and the Dynamics of Antiferromagnetic Ferritin
Temperature-dependent magnetization measurements on a series of synthetic
ferritin proteins containing from 100 to 3000 Fe(III) ions are used to
determine the uncompensated moment of these antiferromagnetic particles. The
results are compared with recent theories of macroscopic quantum coherence
which explicitly include the effect of this excess moment. The scaling of the
excess moment with protein size is consistent with a simple model of finite
size effects and sublattice noncompensation.Comment: 4 pages, 3 Postsript figures, 1 table. Submitted to PR
Transverse Fresnel-Fizeau drag effects in strongly dispersive media
A light beam normally incident upon an uniformly moving dielectric medium is
in general subject to bendings due to a transverse Fresnel-Fizeau light drag
effect. In conventional dielectrics, the magnitude of this bending effect is
very small and hard to detect. Yet, it can be dramatically enhanced in strongly
dispersive media where slow group velocities in the m/s range have been
recently observed taking advantage of the electromagnetically induced
transparency (EIT) effect. In addition to the usual downstream drag that takes
place for positive group velocities, we predict a significant anomalous
upstream drag to occur for small and negative group velocities. Furthermore,
for sufficiently fast speeds of the medium, higher order dispersion terms are
found to play an important role and to be responsible for peculiar effects such
as light propagation along curved paths and the restoration of the spatial
coherence of an incident noisy beam. The physics underlying this new class of
slow-light effects is thoroughly discussed
Mental Fatigue Negatively Influences Manual Dexterity and Anticipation Timing but not Repeated High-intensity Exercise Performance in Trained Adults
Anomalous Self-Energy Effects of the B_1g Phonon in Y_{1-x}(Pr,Ca)_xBa_2Cu_3O_7 Films
In Raman spectra of cuprate superconductors the gap shows up both directly,
via a redistribution of the electronic background, the so-called "2Delta
peaks", and indirectly, e.g. via the renormalization of phononic excitations.
We use a model that allows us to study the redistribution and the related
phonon self-energy effects simultaneously. We apply this model to the B_1g
phonon of Y_{1-x}(Pr,Ca)_xBa_2Cu_3O_7 films, where Pr or Ca substitution
enables us to investigate under- and overdoped samples. While various
self-energy effects can be explained by the strength and energy of the 2\Delta
peaks, anomalies remain. We discuss possible origins of these anomalies.Comment: 6 pages including 4 figure
The Pitt Bacteremia Score Predicts Mortality in Nonbacteremic Infections
Background. Predicting mortality risk in patients is important in research settings. The Pitt bacteremia score (PBS) is commonly used as a predictor of early mortality risk in patients with bloodstream infections (BSIs). We determined whether the PBS predicts 14-day inpatient mortality in nonbacteremia carbapenem-resistant Enterobacteriaceae (CRE) infections. Methods. Patients were selected from the Consortium on Resistance Against Carbapenems in Klebsiella and Other Enterobacteriaceae, a prospective, multicenter, observational study. We estimated risk ratios to analyze the predictive ability of the PBS overall and each of its components individually. We analyzed each component of the PBS in the prediction of mortality, assessed the appropriate cutoff value for the dichotomized score, and compared the predictive ability of the qPitt score to that of the PBS. Results. In a cohort of 475 patients with CRE infections, a PBS 4 was associated with mortality in patients with nonbacteremia infections (risk ratio [RR], 21.9 95% confidence interval [CI], 7.0, 68.8) and with BSIs (RR, 6.0 95% CI, 2.5, 14.4). In multivariable analysis, the hypotension, mechanical ventilation, mental status, and cardiac arrest parameters of the PBS were independent risk factors for 14-day all-cause inpatient mortality. The temperature parameter as originally calculated for the PBS was not independently associated with mortality. However, a temperature < 36.0° C vs 36° C was independently associated with mortality. A qPitt score 2 had similar discrimination as a PBS 4 in nonbacteremia infections. Conclusions. Here, we validated that the PBS and qPitt score can be used as reliable predictors of mortality in nonbacteremia CRE infections
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