637 research outputs found
Biomimetic spatial and temporal (4D) design and fabrication
We imagine the built environment of the future as a ‘bio-hybrid machine for living in’ that will sense and react to activities within the space in order to provide experiences and services that will elevate quality of life while coexisting seamlessly with humans and the natural environment. The study of Hierarchical design in biological materials has the potential to alter the way designers/ engineers/ crafts-men of the future engage with materials in order to realise such visions. We are ex-ploring this design approach using digital manufacturing technologies such as jac-quard weaving and 3D printing
Properties of the Z(3) Interface in (2+1)-D SU(3) Gauge Theory
A study is made of some properties of this interface in the SU(3) pure gauge
theory in 2+1 dimensions. At high temperatures, the interface tension is
measured and shows agreement with the perturbative prediction. Near the
critical temperature, the behaviour of the interface is examined, and its
fluctuations compared to a scalar field theory model.Comment: 4 pages with 4 figures as one uuencoded, gzipped postscript file;
presented at Lattice '9
High-Temperature Properties of the Z(3) Interface in (2+1)-D SU(3) Gauge Theory
We study the high-temperature properties of the Z(3) interface which forms
between the various ordered phases of pure SU(3) gauge theory above a critical
temperature. On a (2+1)-D Euclidean lattice, we perform an accurate measurement
of the interface tension, which shows good agreement with the prediction of
perturbation theory. We also examine the behaviour of the Debye electric
screening mass, and compare this with theoretical predictions.Comment: 10 pages, 3 figures, uuencoded gzipped tar fil
Critical properties of the Z(3) interface in (2+1)-D SU(3) gauge theory
We study the interface between two different Z(3) vacua in the deconfined
phase of SU(3) pure gauge theory in 2+1 dimensions just above the critical
temperature. In simulations of the Euclidean lattice gauge theory formulation
of the system we measure the fluctuations of the interface as the critical
temperature is approached and as a function of system size. We show that the
intrinsic width of the interface remains small even very close to the critical
temperature. Some dynamical exponents which govern the interaction of the
interface with our Monte Carlo algorithm are also estimated. We conclude that
the Z(3) interface has properties broadly similar to those in many other
comparable statistical mechanical systems.Comment: 26 pages, LaTex with 16 postscript figure
Orbital quantization in the high magnetic field state of a charge-density-wave system
A superposition of the Pauli and orbital coupling of a high magnetic field to
charge carriers in a charge-density-wave (CDW) system is proposed to give rise
to transitions between subphases with quantized values of the CDW wavevector.
By contrast to the purely orbital field-induced density-wave effects which
require a strongly imperfect nesting of the Fermi surface, the new transitions
can occur even if the Fermi surface is well nested at zero field. We suggest
that such transitions are observed in the organic metal
-(BEDT-TTF)KHg(SCN) under a strongly tilted magnetic field.Comment: 14 pages including 4 figure
Cyclotron effective masses in layered metals
Many layered metals such as quasi-two-dimensional organic molecular crystals
show properties consistent with a Fermi liquid description at low temperatures.
The effective masses extracted from the temperature dependence of the magnetic
oscillations observed in these materials are in the range, m^*_c/m_e \sim 1-7,
suggesting that these systems are strongly correlated. However, the ratio
m^*_c/m_e contains both the renormalization due to the electron-electron
interaction and the periodic potential of the lattice. We show that for any
quasi-two-dimensional band structure, the cyclotron mass is proportional to the
density of states at the Fermi energy. Due to Luttinger's theorem, this result
is also valid in the presence of interactions. We then evaluate m_c for several
model band structures for the \beta, \kappa, and \theta families of
(BEDT-TTF)_2X, where BEDT-TTF is bis-(ethylenedithia-tetrathiafulvalene) and X
is an anion. We find that for \kappa-(BEDT-TTF)_2X, the cyclotron mass of the
\beta-orbit, m^{*\beta}_c, is close to 2 m^{*\alpha}_c, where m^{*\alpha}_c is
the effective mass of the \alpha- orbit. This result is fairly insensitive to
the band structure details. For a wide range of materials we compare values of
the cyclotron mass deduced from band structure calculations to values deduced
from measurements of magnetic oscillations and the specific heat coefficient.Comment: 12 pages, 3 eps figure
Templates for Convex Cone Problems with Applications to Sparse Signal Recovery
This paper develops a general framework for solving a variety of convex cone
problems that frequently arise in signal processing, machine learning,
statistics, and other fields. The approach works as follows: first, determine a
conic formulation of the problem; second, determine its dual; third, apply
smoothing; and fourth, solve using an optimal first-order method. A merit of
this approach is its flexibility: for example, all compressed sensing problems
can be solved via this approach. These include models with objective
functionals such as the total-variation norm, ||Wx||_1 where W is arbitrary, or
a combination thereof. In addition, the paper also introduces a number of
technical contributions such as a novel continuation scheme, a novel approach
for controlling the step size, and some new results showing that the smooth and
unsmoothed problems are sometimes formally equivalent. Combined with our
framework, these lead to novel, stable and computationally efficient
algorithms. For instance, our general implementation is competitive with
state-of-the-art methods for solving intensively studied problems such as the
LASSO. Further, numerical experiments show that one can solve the Dantzig
selector problem, for which no efficient large-scale solvers exist, in a few
hundred iterations. Finally, the paper is accompanied with a software release.
This software is not a single, monolithic solver; rather, it is a suite of
programs and routines designed to serve as building blocks for constructing
complete algorithms.Comment: The TFOCS software is available at http://tfocs.stanford.edu This
version has updated reference
Macromolecular theory of solvation and structure in mixtures of colloids and polymers
The structural and thermodynamic properties of mixtures of colloidal spheres
and non-adsorbing polymer chains are studied within a novel general
two-component macromolecular liquid state approach applicable for all size
asymmetry ratios. The dilute limits, when one of the components is at infinite
dilution but the other concentrated, are presented and compared to field theory
and models which replace polymer coils with spheres. Whereas the derived
analytical results compare well, qualitatively and quantitatively, with
mean-field scaling laws where available, important differences from ``effective
sphere'' approaches are found for large polymer sizes or semi-dilute
concentrations.Comment: 23 pages, 10 figure
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