311 research outputs found
Decoherence Dynamics in Low-Dimensional Cold Atom Interferometers
We report on a study of the dynamics of decoherence of a matter-wave
interferometer, consisting of a pair of low-dimensional cold atom condensates
at finite temperature. We identify two distinct regimes in the time dependence
of the coherence factor of the interferometer: quantum and classical. Explicit
analytical results are obtained in both regimes. In particular, in the
two-dimensional (2D) case in the classical (long time) regime, we find that the
dynamics of decoherence is universal, exhibiting a power-law decay with an
exponent, proportional to the ratio of the temperature to the
Kosterlitz-Thouless temperature of a single 2D condensate. In the
one-dimensional (1D) case in the classical regime we find a universal
nonanalytic time dependence of decoherence, which is a consequence of the
nonhydrodynamic nature of damping in 1D liquids.Comment: 4 pages, published versio
Anomalous magnetotransport in (YGd)Co alloys: interplay of disorder and itinerant metamagnetism
New mechanism of magnetoresistivity in itinerant metamagnets with a
structural disorder is introduced basing on analysis of experimental results on
magnetoresistivity, susceptibility, and magnetization of structurally
disordered alloys (YGd)Co. In this series, YCo is an
enhanced Pauli paramagnet, whereas GdCo is a ferrimagnet (T=400
K) with Gd sublattice coupled antiferromagnetically to the itinerant Co-3d
electrons. The alloys are paramagnetic for . Large positive
magnetoresistivity has been observed in the alloys with magnetic ground state
at temperatures TT. We show that this unusual feature is linked to
a combination of structural disorder and metamagnetic instability of itinerant
Co-3d electrons. This new mechanism of the magnetoresistivity is common for a
broad class of materials featuring a static magnetic disorder and itinerant
metamagnetism.Comment: 7 pages 7 figure
Decision Support System for Urbanization of the Northern Part of the Volga-Akhtuba Floodplain (Russia) on the Basis of Interdisciplinary Computer Modeling
There is a computer decision support system (CDSS) for urbanization of the
northern part of the Volga-Akhtuba floodplain. This system includes subsystems
of cognitive and game-theoretic analysis, geoinformation and hydrodynamic
simulations. The paper presents the cognitive graph, two-level and three-level
models of hierarchical games for the cases of uncontrolled and controlled
development of the problem situation. We described the quantitative analysis of
the effects of different strategies for the spatial distribution of the
urbanized territories. For this reason we conducted the territory zoning
according to the level of negative consequences of urbanization for various
agents. In addition, we found an analytical solution for games with the linear
dependence of the average flooded area on the urbanized area. We numerically
computed a game equilibrium for dependences derived from the imitational
geoinformation and hydrodynamic modeling of flooding. As the result, we showed
that the transition to the three-level management system and the implementation
of an optimal urbanization strategy minimize its negative consequences.Comment: 14 pages, 5 figures; Conference: Creativity in Intelligent
Technologies and Data Science. CIT&DS 201
Mechanical state assessment using lamb wave technique in static tensile tests
The paper deals with the investigation of Lamb wave ultrasonic technique for damage (or mechanical state) evaluation of AA7068T3 specimens in the course of tensile testing. Two piezoelectric transducers (PZT), one of which is used as an actuator and the other as sensor, were adhesively bonded on the specimen surface using epoxy. Two frequencies of testing signals (60 kHz and 350 kHz) were used. The set of static tensile tests were performed. The recorded signals were processed to calculate the informative parameters in order to evaluate the changes in stress-strain state of the specimens and their microstructure
Experimental Setup for the Measurement of the Thermoelectric Power in Zero and Applied Magnetic Field
An experimental setup was developed for the measurement of the thermoelectric
power (TEP, Seebeck coefficient) in the temperature range from 2 to 350 K and
magnetic fields up to 140 kOe. The system was built to fit in a commercial
cryostat and is versatile, accurate and automated; using two heaters and two
thermometers increases the accuracy of the TEP measurement. High density data
of temperature sweeps from 2 to 350 K can be acquired in under 16 hours and
high density data of isothermal field sweeps from 0 to 140 kOe can be obtained
in under 2 hours. Calibrations for the system have been performed on a platinum
wire and BiSrCaCuO high superconductors.
The measured TEP of phosphor-bronze (voltage lead wire) turns to be very small,
where the absolute TEP value of phosphor-bronze wire is much less than 0.5
V/K below 80 K. For copper and platinum wires measured against to the
phosphor-bronze wire, the agreement between measured results and the literature
data is good. To demonstrate the applied magnetic field response of the system,
we report measurements of the TEP on single crystal samples of LaAgSb and
CeAgSb in fields up to 140 kOe.Comment: 10 pages, 8 figures. accepted in Measurement Science and Technolog
Theory of Ferromagnetism in Doped Excitonic Condensates
Nesting in a semimetal can lead to an excitonic insulator state with
spontaneous coherence between conduction and valence bands and a gap for
charged excitations. In this paper we present a theory of the ferromagnetic
state that occurs when the density of electrons in the conduction band and
holes in the valence band differ. We find an unexpectedly rich doping-field
phase diagram and an unusual collective excitation spectrum that includes two
gapless collective modes. We predict regions of doping and external field in
which phase-separated condensates of electrons and holes with parallel spins
and opposing spins coexist.Comment: 5 pages, 3 postscript file
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