1,958 research outputs found
Benchmarking the nonperturbative functional renormalization group approach on the random elastic manifold model in and out of equilibrium
Criticality in the class of disordered systems comprising the random-field
Ising model (RFIM) and elastic manifolds in a random environment is controlled
by zero-temperature fixed points that must be treated through a functional
renormalization group. We apply the nonperturbative functional renormalization
group approach that we have previously used to describe the RFIM in and out of
equilibrium [Balog-Tarjus-Tissier, Phys. Rev. B 97, 094204 (2018)] to the
simpler and by now well-studied case of the random elastic manifold model. We
recover the main known properties, critical exponents and scaling functions, of
both the pinned phase of the manifold at equilibrium and the depinning
threshold in the athermally and quasi-statically driven case for any dimension
. This successful benchmarking of our theoretical approach gives
strong support to the results that we have previously obtained for the RFIM, in
particular concerning the distinct universality classes of the equilibrium and
out-of-equilibrium (hysteresis) critical points below a critical dimension
.Comment: 38 pages, 6 figure
Criticality of the random field Ising model in and out of equilibrium: a nonperturbative functional renormalization group description
We show that, contrary to previous suggestions based on computer simulations
or erroneous theoretical treatments, the critical points of the random-field
Ising model out of equilibrium, when quasi-statically changing the applied
source at zero temperature, and in equilibrium are not in the same universality
class below some critical dimension . We demonstrate this by
implementing a non-perturbative functional renormalization group for the
associated dynamical field theory. Above , the avalanches, which
characterize the evolution of the system at zero temperature, become irrelevant
at large distance, and hysteresis and equilibrium critical points are then
controlled by the same fixed point. We explain how to use computer simulation
and finite-size scaling to check the correspondence between in and out of
equilibrium criticality in a far less ambiguous way than done so far.Comment: 23 pages, 19 figure
Manipulation of edge states in microwave artificial graphene
Edge states are one important ingredient to understand transport properties
of graphene nanoribbons. We study experimentally the existence and the internal
structure of edge states under uniaxial strain of the three main edges: zigzag,
bearded, and armchair. The experiments are performed on artificial microwave
graphene flakes, where the wavefunctions are obtained by direct imaging. We
show that uniaxial strain can be used to manipulate the edge states: a single
parameter controls their existence and their spatial extension into the ribbon.
By combining tight-binding approach and topological arguments, we provide an
accurate description of our experimental findings. A new type of zero-energy
state appearing at the intersection of two edges, namely the corner state, is
also observed and discussed.Comment: 15 pages, 9 figure
Deformable Part-based Fully Convolutional Network for Object Detection
Existing region-based object detectors are limited to regions with fixed box
geometry to represent objects, even if those are highly non-rectangular. In
this paper we introduce DP-FCN, a deep model for object detection which
explicitly adapts to shapes of objects with deformable parts. Without
additional annotations, it learns to focus on discriminative elements and to
align them, and simultaneously brings more invariance for classification and
geometric information to refine localization. DP-FCN is composed of three main
modules: a Fully Convolutional Network to efficiently maintain spatial
resolution, a deformable part-based RoI pooling layer to optimize positions of
parts and build invariance, and a deformation-aware localization module
explicitly exploiting displacements of parts to improve accuracy of bounding
box regression. We experimentally validate our model and show significant
gains. DP-FCN achieves state-of-the-art performances of 83.1% and 80.9% on
PASCAL VOC 2007 and 2012 with VOC data only.Comment: Accepted to BMVC 2017 (oral
Tight-binding couplings in microwave artificial graphene
We experimentally study the propagation of microwaves in an artificial
honeycomb lattice made of dielectric resonators. This evanescent propagation is
well described by a tight-binding model, very much like the propagation of
electrons in graphene. We measure the density of states, as well as the wave
function associated with each eigenfrequency. By changing the distance between
the resonators, it is possible to modulate the amplitude of
next-(next-)nearest-neighbor hopping parameters and to study their effect on
the density of states. The main effect is the density of states becoming
dissymmetric and a shift of the energy of the Dirac points. We study the basic
elements: An isolated resonator, a two-level system, and a square lattice. Our
observations are in good agreement with analytical solutions for corresponding
infinite lattice.Comment: 10 pages, 9 figure
- …