77,930 research outputs found
The Edge Electric Field of a Pyroelectric and its Applications
Following a change of temperature of a pyroelectric (PE), a depolarizing
electric field appears both inside the PE, as well as outside its edges, the
edge depolarizing electric field (EDEF). The EDEF extends outwards up to a
distance of the order of magnitude of the PE width. The mapping and the
strength of the EDEF have been calculated and analyzed for the case of a
semi-infinite pyroelectric plate. This strong EDEF (104-105 V/cm), when
penetrating into the surrounding medium, creates a variety of physical effects:
inducing electrical current in a semiconductor and affecting its resistance,
accelerating charged and neutral particles in vacuum or in a gas, generating
electromagnetic waves, modifying optical characteristics by electrooptical and
photoelasic effects, generating piezoelectric deformation and more. We show
that these EDEF induced effects could serve as a basis for the development of
various applications and devices.Comment: 27 pages including 13 figure
Checking the transverse Ward-Takahashi relation at one loop order in 4-dimensions
Some time ago Takahashi derived so called {\it transverse} relations relating
Green's functions of different orders to complement the well-known
Ward-Green-Takahashi identities of gauge theories by considering wedge rather
than inner products. These transverse relations have the potential to determine
the full fermion-boson vertex in terms of the renormalization functions of the
fermion propagator. He & Yu have given an indicative proof at one-loop level in
4-dimensions. However, their construct involves the 4th rank Levi-Civita tensor
defined only unambiguously in 4-dimensions exactly where the loop integrals
diverge. Consequently, here we explicitly check the proposed transverse
Ward-Takahashi relation holds at one loop order in -dimensions, with
.Comment: 20 pages, 3 figures This version corrects and clarifies the previous
result. This version has been submitted for publicatio
Stabilized Schemes for the Hydrostatic Stokes Equations
Some new stable finite element (FE) schemes are presented for the hydrostatic Stokes
system or primitive equations of the ocean. It is known that the stability of the mixed formulation ap-
proximation for primitive equations requires the well-known LadyzhenskayaâBabuËskaâBrezzi condi-
tion related to the Stokes problem and an extra inf-sup condition relating the pressure and the vertical
velocity.
The main goal of this paper is to avoid this extra condition by adding a residual stabilizing term to the
vertical momentum equation. Then, the stability for Stokes-stable FE combinations is extended to
the primitive equations and some error estimates are provided using TaylorâHood P2 âP1 or miniele-
ment (P1 +bubble)âP1 FE approximations, showing the optimal convergence rate in the P2 âP1 case.
These results are also extended to the anisotropic (nonhydrostatic) problem. On the other hand,
by adding another residual term to the continuity equation, a better approximation of the vertical
derivative of pressure is obtained. In this case, stability and error estimates including this better
approximation are deduced, where optimal convergence rate is deduced in the (P 1 +bubble)âP1 case.
Finally, some numerical experiments are presented supporting previous results
Random Time-Scale Invariant Diffusion and Transport Coefficients
Single particle tracking of mRNA molecules and lipid granules in living cells
shows that the time averaged mean squared displacement of
individual particles remains a random variable while indicating that the
particle motion is subdiffusive. We investigate this type of ergodicity
breaking within the continuous time random walk model and show that
differs from the corresponding ensemble average. In
particular we derive the distribution for the fluctuations of the random
variable . Similarly we quantify the response to a
constant external field, revealing a generalization of the Einstein relation.
Consequences for the interpretation of single molecule tracking data are
discussed.Comment: 4 pages, 4 figures.Article accompanied by a PRL Viewpoint in
Physics1, 8 (2008
Bandwidth-disorder phase diagram of half doped layered manganites
Phase diagrams in the plane of (the average ionic radius, related to
one-electron bandwidth ) and (the ionic radius variance,
measuring the quenched disorder), or ``bandwidth-disorder phase diagrams'',
have been established for perovskite manganites, with three-dimensional (3)
Mn-O network. Here we establish the intrinsic bandwidth-disorder phase diagram
of half-doped layered manganites with the two-dimensional (2) Mn-O network,
examining in detail the ``mother state'' of the colossal magnetoresistance
(CMR) phenomenon in crystals without ferromagnetic instability. The
consequences of the reduced dimensionality, from 3 to 2, on the
order-disorder phenomena in the charge-orbital sectors are also highlighted.Comment: REVTeX 4 style; 5 pages, 4 figure
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Composite genus one Belyi maps
Motivated by a demand for explicit genus 1 Belyi maps from theoretical physics, we give an efficient method of explicitly computing genus one Belyi maps by (1) composing covering maps from elliptic curves to the Riemann sphere with simpler (univariate) genus zero Belyi maps, as well as by (2) composing further with isogenies between elliptic curves. The computed examples of genus 1 Belyi maps has doubly-periodic dessins dâenfant that are listed in the physics literature as so-called brane-tilings in the context of quiver gauge theorie
Topological phase due to electric dipole moment and magnetic monopole interaction
We show that there is an anologous Aharonov-Casher effect on a neutral
particle with electric dipole moment interacting with a magnetic filed produced
by magnetic monopoles.Comment: 8 page
Early detection of rice blast (Pyricularia) at seedling stage in Nipponbare rice variety using near-infrared hyper-spectral image
Blast rice is the worst biological disaster in rice cultivation. It reduces the yield at least up to 40 to 50% (in the worst period of disease). In this study, the near-infrared hyper-spectral image was investigated to detect blast rice in Nipponbare at seedling stage. Two hundred rice seedlings were segregated into two classes: infected and healthy. All of rice seedlings were scanned with a hyper-spectral imaging system in the NIR (900 to 1700 nm) wavelength range. Principal component analysis (PCA) was performed on the images and the distribution of PCA scores within individual leaf were measured to develop linear discriminant analysis (LDA) models for predicting the infected leaves from healthy leaves. An LDA model classified all the leaves into infected and healthy categories, with an overall accuracy of 92% on validation set. Meanwhile, the classification model base on five selected wavelengths (1188, 1339, 1377, 1432 and 1614 nm) was comparable to that base on the full-spectrum image data.Key words: Rice blast (Pyricularia), Nipponbare, near-infrared hyper-spectral image, principal component analysis, linear discriminant analysis
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