14,377 research outputs found
Scaling Theory for Steady State Plastic Flows in Amorphous Solids
Strongly correlated amorphous solids are a class of glass-formers whose
inter-particle potential admits an approximate inverse power-law form in a
relevant range of inter-particle distances. We study the steady-state plastic
flow of such systems, firstly in the athermal, quasi-static limit, and secondly
at finite temperatures and strain rates. In all cases we demonstrate the
usefulness of scaling concepts to reduce the data to universal scaling
functions where the scaling exponents are determined a-priori from the
inter-particle potential. In particular we show that the steady plastic flow at
finite temperatures with efficient heat extraction is uniquely characterized by
two scaled variables; equivalently, the steady state displays an equation of
state that relates one scaled variable to the other two. We discuss the range
of applicability of the scaling theory, and the connection to density scaling
in supercooled liquid dynamics. We explain that the description of transient
states calls for additional state variables whose identity is still far from
obvious.Comment: 9 pages, 9 figure
The distribution of forces affects vibrational properties in hard sphere glasses
We study theoretically and numerically the elastic properties of hard sphere
glasses, and provide a real-space description of their mechanical stability. In
contrast to repulsive particles at zero-temperature, we argue that the presence
of certain pairs of particles interacting with a small force soften elastic
properties. This softening affects the exponents characterizing elasticity at
high pressure, leading to experimentally testable predictions. Denoting
the force distribution of such pairs and the
packing fraction at which pressure diverges, we predict that (i) the density of
states has a low-frequency peak at a scale , rising up to it as
, and decaying above as where and is the frequency,
(ii) shear modulus and mean-squared displacement are inversely proportional
with where
, and (iii) continuum elasticity breaks down on a
scale where
and , where is the
coordination and the spatial dimension. We numerically test (i) and provide
data supporting that in our bi-disperse system,
independently of system preparation in two and three dimensions, leading to
, , and . Our results for the
mean-square displacement are consistent with a recent exact replica computation
for , whereas some observations differ, as rationalized by the
present approach.Comment: 5 pages + 4 pages supplementary informatio
Analysis of microwave radiometric measurements from Skylab
There are no author-identified significant results in this report
Fluctuational susceptibility of ultracold bosons in the vicinity of condensation
We study the behaviour of ultracold bosonic gas in the critical region above
the Bose-Einstein condensation in the presence of an artificial magnetic field,
. We show that the condensate fluctuations above the critical
temperature cause the fluctuational susceptibility, ,
of a uniform gas to have a stronger power-law divergence than in an analogous
superconducting system. Measuring such a divergence opens new ways of exploring
critical properties of the ultracold gas and an opportunity of an accurate
determination of . We describe a method of measuring
which requires a constant gradient in and suggest a way of
creating such a field in experiment.Comment: 5 pages, 3 figures, 5 pages of Supplement; the text is rewritten and
rearranged, and the figures are modifie
Dimensional Crossover of the Dephasing Time in Disordered Mesoscopic Rings: From Diffusive through Ergodic to 0D Behavior
We analyze dephasing by electron interactions in a small disordered quasi-one
dimensional (1D) ring weakly coupled to leads, where we recently predicted a
crossover for the dephasing time \tPh(T) from diffusive or ergodic 1D
(\tPh^{-1} \propto T^{2/3}, T^{1}) to behavior (\tPh^{-1} \propto
T^{2}) as drops below the Thouless energy \ETh. We provide a detailed
derivation of our results, based on an influence functional for quantum Nyquist
noise, and calculate all leading and subleading terms of the dephasing time in
the three regimes. Explicitly taking into account the Pauli blocking of the
Fermi sea in the metal allows us to describe the regime on equal footing
as the others. The crossover to , predicted by Sivan, Imry and Aronov for
3D systems, has so far eluded experimental observation. We will show that for
T \ll \ETh, dephasing governs not only the -dependence for the smooth
part of the magnetoconductivity but also for the amplitude of the
Altshuler-Aronov-Spivak oscillations, which result only from electron paths
winding around the ring. This observation can be exploited to filter out and
eliminate contributions to dephasing from trajectories which do not wind around
the ring, which may tend to mask the behavior. Thus, the ring geometry
holds promise of finally observing the crossover to experimentally.Comment: in "Perspectives of Mesoscopic Physics - Dedicated to Yoseph Imry's
70th Birthday", edited by Amnon Aharony and Ora Entin-Wohlman (World
Scientific, 2010), chap. 20, p. 371-396, ISBN-13 978-981-4299-43-
Pseudo diamagnetism of four component exciton condensates
We analyze the spin structure of the ground state of four-component exciton
condensates in coupled quantum wells as a function of spin-dependent
interactions and applied magnetic field. The four components correspond to the
degenerate exciton states characterized by and spin projections
to the axis of the structure. We show that in a wide range of parameters, the
chemical potential of the system increases as a function of magnetic field,
which manifests a pseudo-diamagnetism of the system. The transitions to
polarized two- and one-component condensates can be of the first-order in this
case. The predicted effects are caused by energy conserving mixing of
and excitons.Comment: 4 pages, 2 figure
Statistical Physics of Elasto-Plastic Steady States in Amorphous Solids: Finite Temperatures and Strain Rates
The effect of finite temperature and finite strain rate on
the statistical physics of plastic deformations in amorphous solids made of
particles is investigated. We recognize three regimes of temperature where the
statistics are qualitatively different. In the first regime the temperature is
very low, , and the strain is quasi-static. In this regime
the elasto-plastic steady state exhibits highly correlated plastic events whose
statistics are characterized by anomalous exponents. In the second regime
the system-size dependence of the
stress fluctuations becomes normal, but the variance depends on the strain
rate. The physical mechanism of the cross-over is different for increasing
temperature and increasing strain rate, since the plastic events are still
dominated by the mechanical instabilities (seen as an eigenvalue of the Hessian
matrix going to zero), and the effect of temperature is only to facilitate the
transition. A third regime occurs above the second cross-over temperature
where stress fluctuations become dominated by thermal
noise. Throughout the paper we demonstrate that scaling concepts are highly
relevant for the problem at hand, and finally we present a scaling theory that
is able to collapse the data for all the values of temperatures and strain
rates, providing us with a high degree of predictability.Comment: 12 pages, 13 figure
Structured Improvisation Counseling: A Study of the Use of Ritual and Drama in Homogeneous and Multicultural Settings
The University Archives has determined that this item is of continuing value to OSU's history.Session 7: Enhancing Social Work Practice with Special Groups. Presenter: Janet M. Lerner, D.S.W., Columbia University (1988) - "Structured Improvisation Counseling: A Study of the Use of Ritual and Drama in Homogeneous and Multicultural Settings".The Ohio State University College of Social Wor
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