9,395 research outputs found
Existence and approximation of Hunt processes associated with generalized Dirichlet forms
We show that any strictly quasi-regular generalized Dirichlet form that
satisfies the mild structural condition D3 is associated to a Hunt process, and
that the associated Hunt process can be approximated by a sequence of
multivariate Poisson processes. This also gives a new proof for the existence
of a Hunt process associated to a strictly quasi-regular generalized Dirichlet
form that satisfies SD3 and extends all previous results.Comment: Revised, shortened and improved versio
Anomalous phonon behavior in the high temperature shape memory alloy: TiPd:Cr
Ti50 Pd50-xCrx is a high temperature shape memory alloy with a martensitic
transformation temperature strongly dependent on the Cr composition. Prior to
the transformation a premartensitic phase is present with an incommensurate
modulated cubic lattice with wave vector of q0=(0.22, 0.22, 0). The temperature
dependence of the diffuse scattering in the cubic phase is measured as a
function temperature for x=6.5, 8.5, and 10 at. %. The lattice dynamics has
been studied and reveals anomalous temperature and q-dependence of the
[110]-TA2 transverse phonon branch. The phonon linewidth is broad over the
entire Brillouin zone and increases with decreasing temperature, contrary to
the behavior expected for anharmonicity. No anomaly is observed at q0. The
results are compared with first principles calculation of the phonon structure.Comment: 26 pages, 11 figure
Self Consistent Expansion for the Molecular Beam Epitaxy Equation
Motivated by a controversy over the correct results derived from the dynamic
renormalization group (DRG) analysis of the non linear molecular beam epitaxy
(MBE) equation, a self-consistent expansion (SCE) for the non linear MBE theory
is considered. The scaling exponents are obtained for spatially correlated
noise of the general form . I find a lower critical dimension , above, which the linear MBE solution appears. Below the
lower critical dimension a r-dependent strong-coupling solution is found. These
results help to resolve the controversy over the correct exponents that
describe non linear MBE, using a reliable method that proved itself in the past
by predicting reasonable results for the Kardar-Parisi-Zhang (KPZ) system,
where DRG failed to do so.Comment: 16 page
Changing of flight phenology and ecotype expansion of the European corn borer (Ostrinia nubilalis Hbn.) in Hungary Part
The studies aimed to acquire the widest possible information on the annual flight in Hungary of the European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Pyralidae). The investigations used biomathematical (Part 1) and graphical (Part 2) evaluation to document changes in the individual population number.The study was conducted in Hungary using ECB moth capture records from the Plant Protection Information System black light trap system (1991–2004). We have drawn conclusions on the appearance of annual flights and the tendency of alterations in flight direction by means of light trap results in four different areas in Hungary. We calculated the flight peak quotients, the individual population numbers of the second flight peak, the distinctions of individual numbers of two flight peaks in this part.As previously published, alterations in flight direction of ECB flights began at different times in Hungary. In the current study, a gradual disappearance of the univoltine ecotype and gradual appearance of the bivoltine ecotype ECB in Hungary is confirmed by the data obtained between 1991–2004. Flight peak quotients and data concerning the second flight peak have confirmed change this process, too: the appearance of a second flight peak in Northwestern Hungary from 1995–1996 (FP = 1.27), the more significant appearance of flights in August in Western Hungary (FP = 1.05) and Northeastern Hungary (FP = 1.45), and a three and four times more individual number of the second flight peak in Southeastern Hungary (FP = 3.44). Flight peak quotients, individual population numbers of the second flight peak, the tendency towards a difference in population number of the two peaks, and size of increase of these values demonstrates the southeastern-northwestern presence of the bivoltine ecotype in Hungary
Predictability of Self-Organizing Systems
We study the predictability of large events in self-organizing systems. We
focus on a set of models which have been studied as analogs of earthquake
faults and fault systems, and apply methods based on techniques which are of
current interest in seismology. In all cases we find detectable correlations
between precursory smaller events and the large events we aim to forecast. We
compare predictions based on different patterns of precursory events and find
that for all of the models a new precursor based on the spatial distribution of
activity outperforms more traditional measures based on temporal variations in
the local activity.Comment: 15 pages, plain.tex with special macros included, 4 figure
A Classification of 3-Family Grand Unification in String Theory I. The SO(10) and E_6 Models
We give a classification of 3-family SO(10) and E_6 grand unification in
string theory within the framework of conformal field theory and asymmetric
orbifolds. We argue that the construction of such models in the heterotic
string theory requires certain Z_6 asymmetric orbifolds that include a Z_3
outer-automorphism, the latter yielding a level-3 current algebra for the grand
unification gauge group SO(10) or E_6. We then classify all such Z_6 asymmetric
orbifolds that result in models with a non-abelian hidden sector. All models
classified in this paper have only one adjoint (but no other higher
representation) Higgs field in the grand unified gauge group. In addition, all
of them are completely anomaly free. There are two types of such 3-family
models. The first type consists of the unique SO(10) model with SU(2) X SU(2) X
SU(2) as its hidden sector (which is not asymptotically-free at the string
scale). This SO(10) model has 4 left-handed and 1 right-handed 16s. The second
type is described by a moduli space containing 17 models (distinguished by
their massless spectra). All these models have an SU(2) hidden sector, and 5
left-handed and 2 right-handed families in the grand unified gauge group. One
of these models is the unique E_6 model with an asymptotically-free SU(2)
hidden sector. The others are SO(10) models, 8 of them with an asymptotically
free hidden sector at the string scale.Comment: 35 pages, Revtex 3.0, one eps figure (to appear in Phys. Rev. D
Pressure balance at the magnetopause: Experimental studies
The pressure balance at the magnetopause is formed by magnetic field and
plasma in the magnetosheath, on one side, and inside the magnetosphere, on the
other side. In the approach of dipole earth's magnetic field configuration and
gas-dynamics solar wind flowing around the magnetosphere, the pressure balance
predicts that the magnetopause distance R depends on solar wind dynamic
pressure Pd as a power low R ~ Pd^alpha, where the exponent alpha=-1/6. In the
real magnetosphere the magnetic filed is contributed by additional sources:
Chapman-Ferraro current system, field-aligned currents, tail current, and
storm-time ring current. Net contribution of those sources depends on
particular magnetospheric region and varies with solar wind conditions and
geomagnetic activity. As a result, the parameters of pressure balance,
including power index alpha, depend on both the local position at the
magnetopause and geomagnetic activity. In addition, the pressure balance can be
affected by a non-linear transfer of the solar wind energy to the
magnetosheath, especially for quasi-radial regime of the subsolar bow shock
formation proper for the interplanetary magnetic field vector aligned with the
solar wind plasma flow.Comment: 8 pages, 2 figure
Random-Phase Solitons in Nonlinear Periodic Lattices
We predict the existence of random phase solitons in nonlinear periodic lattices. These solitons exist when the nonlinear response time is much longer than the characteristic time of random phase fluctuations. The intensity profiles, power spectra, and statistical (coherence) properties of these stationary waves conform to the periodicity of the lattice. The general phenomenon of such solitons is analyzed in the context of nonlinear photonic lattices
Recognition of 3-D Objects from Multiple 2-D Views by a Self-Organizing Neural Architecture
The recognition of 3-D objects from sequences of their 2-D views is modeled by a neural architecture, called VIEWNET that uses View Information Encoded With NETworks. VIEWNET illustrates how several types of noise and varialbility in image data can be progressively removed while incornplcte image features are restored and invariant features are discovered using an appropriately designed cascade of processing stages. VIEWNET first processes 2-D views of 3-D objects using the CORT-X 2 filter, which discounts the illuminant, regularizes and completes figural boundaries, and removes noise from the images. Boundary regularization and cornpletion are achieved by the same mechanisms that suppress image noise. A log-polar transform is taken with respect to the centroid of the resulting figure and then re-centered to achieve 2-D scale and rotation invariance. The invariant images are coarse coded to further reduce noise, reduce foreshortening effects, and increase generalization. These compressed codes are input into a supervised learning system based on the fuzzy ARTMAP algorithm. Recognition categories of 2-D views are learned before evidence from sequences of 2-D view categories is accumulated to improve object recognition. Recognition is studied with noisy and clean images using slow and fast learning. VIEWNET is demonstrated on an MIT Lincoln Laboratory database of 2-D views of jet aircraft with and without additive noise. A recognition rate of 90% is achieved with one 2-D view category and of 98.5% correct with three 2-D view categories.National Science Foundation (IRI 90-24877); Office of Naval Research (N00014-91-J-1309, N00014-91-J-4100, N00014-92-J-0499); Air Force Office of Scientific Research (F9620-92-J-0499, 90-0083
Cyclotron motion in graphene
We investigate cyclotron motion in graphene monolayers considering both the
full quantum dynamics and its semiclassical limit reached at high carrier
energies. Effects of zitterbewegung due to the two dispersion branches of the
spectrum dominate the irregular quantum motion at low energies and are obtained
as a systematic correction to the semiclassical case. Recent experiments are
shown to operate in the semiclassical regime.Comment: 6 pages, 1 figure include
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