2,129 research outputs found
General Lin-Maldacena solutions and PWMM Instantons from supergravity
We use the Lin-Maldacena prescription to demonstrate how to find the
supergravity solutions dual to arbitrary vacua of the plane wave matrix model
and maximally supersymmetric Yang-Mills theory on RxS^2, by solving the
auxiliary electrostatics problem. We then apply the technique to study
instantons at strong coupling in the matrix model.Comment: 15 pages, 4 figures. Minor correctio
Holographic Non-Fermi Liquids and the Luttinger Theorem
We show that the Luttinger theorem, a robust feature of Fermi liquids, can be
violated in non-Fermi liquids. We compute non-Fermi liquid Green functions
using duality to black holes and find that the volume of the Fermi surface
depends exponentially on the scaling dimension, which is a measure of the
coupling. This demonstrates that Luttinger's theorem does not extend to
non-Fermi liquids. We comment on possible experimental signatures.Comment: 11 pages, 2 figure
Accelerating the solution of families of shifted linear systems with CUDA
We describe the GPU implementation of shifted or multimass iterative solvers
for sparse linear systems of the sort encountered in lattice gauge theory. We
provide a generic tool that can be used by those without GPU programming
experience to accelerate the simulation of a wide array of theories. We stress
genericity, which is important to allow the simulation of candidate theories
for new physics at LHC, and for the study of various supersymmetric theories.
We find significant speed ups, which we conservatively bound below at at least
twelve times, that promise to put a variety of research questions within
practical reach.Comment: v2: added referenc
Predicting colloidal crystals from shapes via inverse design and machine learning
A fundamental challenge in materials design is linking building block
attributes to crystal structure. Addressing this challenge is particularly
difficult for systems that exhibit emergent order, such as entropy-stabilized
colloidal crystals. We combine recently developed techniques in inverse design
with machine learning to construct a model that correctly classifies the
crystals of more than ten thousand polyhedral shapes into 13 different
structures with a predictive accuracy of 96% using only two geometric shape
measures. With three measures, 98% accuracy is achieved. We test our model on
previously reported colloidal crystal structures for 71 symmetric polyhedra and
obtain 92% accuracy. Our findings (1) demonstrate that entropic colloidal
crystals are controlled by surprisingly few parameters, (2) provide a
quantitative model to predict these crystals solely from the geometry of their
building blocks, and (3) suggest a prediction paradigm that easily generalizes
to other self-assembled materials.Comment: 4 figure
Mapping Disorder in Entropically Ordered Crystals
Systems of hard shapes crystallize due to entropy. How is entropy distributed
among translational and rotational microscopic contributions? We answer this
question by decomposing thermal fluctuation of crystals of hard hexagons into
collective modes, a generalization and quantification of the Onsager picture of
hard rod liquid crystals. We show that at densities both near densest packing
and near the solid-hexatic melting transition, solids of hard regular hexagons
hold most of their entropy in translational degrees of freedom.Comment: 5 REVTeX pages, 3 figure
Relevance of Packing to Colloidal Self-Assembly
Since the 1920s, packing arguments have been used to rationalize crystal
structures in systems ranging from atomic mixtures to colloidal crystals.
Packing arguments have recently been applied to complex nanoparticle
structures, where they often, but not always, work. We examine when, if ever,
packing is a causal mechanism in hard particle approximations of colloidal
crystals. We investigate three crystal structures comprised of their ideal
packing shapes. We show that, contrary to expectations, the ordering mechanism
cannot be packing, even when the thermodynamically self-assembled structure is
the same as that of the densest packing. We also show that the best particle
shapes for hard particle colloidal crystals in the infinite pressure limit are
imperfect versions of the ideal packing shape.Comment: 6 page
Robust Design in Systems Physics
Ensuring robust outcomes and designs is a crucial challenge in the
engineering of modern integrated systems that are comprised of many
heterogeneous subsystems. Coupling among heterogeneous subsystems leads to the
complex response of design elements to changes in whole-system specifications.
Here, we show that the response of design elements to whole-system
specification changes can be characterized, as materials are, using strong/weak
and brittle/ductile dichotomies. We find these dichotomies emerge from a
mesoscale treatment of early stage design problems that we cast in terms of
stress--strain relationships. We illustrate the use of this approach with
examples from naval engineering, however our approach is immediately applicable
to a broad range of problems in integrated systems design.Comment: 8 ReVTeX pages, 4 figure
Little String Theory from a Double-Scaled Matrix Model
Following Lin and Maldacena, we find exact supergravity solutions dual to a
class of vacua of the plane wave matrix model by solving an electrostatics
problem. These are asymptotically near-horizon D0-brane solutions with a throat
associated with NS5-brane degrees of freedom. We determine the precise limit
required to decouple the asymptotic geometry and leave an infinite throat
solution found earlier by Lin and Maldacena, dual to Little String Theory on
S^5. By matching parameters with the gauge theory, we find that this
corresponds to a double scaling limit of the plane wave matrix model in which N
\to \infty and the 't Hooft coupling \lambda scales as \ln^4(N), which we
speculate allows all terms in the genus expansion to contribute even at
infinite N. Thus, the double-scaled matrix quantum mechanics gives a Lagrangian
description of Little String Theory on S^5, or equivalently a ten-dimensional
string theory with linear dilaton background.Comment: 31 pages, LaTeX, 3 figures. Correction of typos in the appendice
Crossover Behavior in the Packing and Assembly of Multivalent Lock-and-Key Colloids
Emergent behaviors occur in a vast array of systems across many scales, and
are of fundamental physical importance because of the intrinsic difficulty in
linking microscopic system properties to macroscopic behaviors. Here we study
the emergent self-assembly behavior of model systems of recently synthesized
families of concave dimpled hard spheres, or lock-and-key colloids. We find
that as dimple size increases each family exhibits a crossover from a structure
that does not reflect the particle symmetry to one that does and, surprisingly,
the point at which this crossover occurs is approximately independent of the
particle symmetry. Using a combination of numerical and analytic techniques we
study systems at infinite and finite pressure, and find different common
control parameters in each limit. Our results suggest there exists a set of
experimentally realizable colloidal systems that exhibit complex emergent
behaviors that can be traced to a common underlying microscopic control
parameter.Comment: V2: 18 pages, 22 figures. Revised text with clarifications,
corrections, and additional supporting dat
Shape Driven Solid--Solid Transitions in Colloids
Despite the fundamental importance of solid--solid transitions for
metallurgy, ceramics, earth science, reconfigurable materials, and colloidal
matter, the details of how materials transform between two solid structures are
poorly understood. We introduce a class of {simple} model systems in which the
direct control of local order, via colloid shape change, induces solid--solid
phase transitions, and characterize how the transitions happen
thermodynamically. We find that within a single shape family there are
solid--solid transitions that can occur with or without a thermal activation
barrier. Our results provide new means for the study of solid--solid phase
transitions, and have implications for designing reconfigurable materials.Comment: 8 REVTeX pages, 7 figure
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