14,443 research outputs found
d-Wave Checkerboard Order in Cuprates
We show that the d-wave ordering in particle-hole channels, dubbed d-wave
checkerboard order, possesses important physics that can sufficiently explain
the scanning tunneling microscopy (STM) results in cuprates. A weak d-wave
checkerboard order can effectively suppress the coherence peak in the
single-particle spectrum while leaving the spectrum along the nodal direction
almost unaffected. Simultaneously, it generates a Fermi arc with little
dispersion around the nodal points at finite temperature that is consistent
with the results of angle-resolved photoemission spectroscopy (ARPES)
experiments in the pseudogap phase. We also show that there is a general
complementary connection between the d-wave checkerboard order and the
pair-density-wave order. Suppressing superconductivity locally or globally
through phase fluctuations should induce both orders in underdoped cuprates and
explain the nodal-antinodal dichotomy observed in ARPES and STM experiments
Image Question Answering using Convolutional Neural Network with Dynamic Parameter Prediction
We tackle image question answering (ImageQA) problem by learning a
convolutional neural network (CNN) with a dynamic parameter layer whose weights
are determined adaptively based on questions. For the adaptive parameter
prediction, we employ a separate parameter prediction network, which consists
of gated recurrent unit (GRU) taking a question as its input and a
fully-connected layer generating a set of candidate weights as its output.
However, it is challenging to construct a parameter prediction network for a
large number of parameters in the fully-connected dynamic parameter layer of
the CNN. We reduce the complexity of this problem by incorporating a hashing
technique, where the candidate weights given by the parameter prediction
network are selected using a predefined hash function to determine individual
weights in the dynamic parameter layer. The proposed network---joint network
with the CNN for ImageQA and the parameter prediction network---is trained
end-to-end through back-propagation, where its weights are initialized using a
pre-trained CNN and GRU. The proposed algorithm illustrates the
state-of-the-art performance on all available public ImageQA benchmarks
Complementary Pair Density Wave and d-wave Checkerboard Order in High Temperature Superconductors
The competing orders in the particle-particle (P-P) channel and the
particle-hole (P-H) channel have been proposed separately to explain the
pseudogap physics in cuprates. By solving the Bogoliubov-deGennes equation
self-consistently, we show that there is a general complementary connection
between the d-wave checkerboard order (DWCB) in the particle-hole (P-H) channel
and the pair density wave order (PDW) in the particle-particle (P-P) channel. A
small pair density localization generates DWCB and PDW orders simultaneously.
The result suggests that suppressing superconductivity locally or globally
through phase fluctuation should induce both orders in underdoped cuprates. The
presence of both DWCB and PDW orders with periodicity can
explain the checkerboard modulation observed in FT-STS from STM and the
puzzling dichotomy between the nodal and antinodal regions as well as the
characteristic features such as non-dispersive Fermi arc in the pseudogap
state
Topology-Guided Path Integral Approach for Stochastic Optimal Control in Cluttered Environment
This paper addresses planning and control of robot motion under uncertainty
that is formulated as a continuous-time, continuous-space stochastic optimal
control problem, by developing a topology-guided path integral control method.
The path integral control framework, which forms the backbone of the proposed
method, re-writes the Hamilton-Jacobi-Bellman equation as a statistical
inference problem; the resulting inference problem is solved by a sampling
procedure that computes the distribution of controlled trajectories around the
trajectory by the passive dynamics. For motion control of robots in a highly
cluttered environment, however, this sampling can easily be trapped in a local
minimum unless the sample size is very large, since the global optimality of
local minima depends on the degree of uncertainty. Thus, a homology-embedded
sampling-based planner that identifies many (potentially) local-minimum
trajectories in different homology classes is developed to aid the sampling
process. In combination with a receding-horizon fashion of the optimal control
the proposed method produces a dynamically feasible and collision-free motion
plans without being trapped in a local minimum. Numerical examples on a
synthetic toy problem and on quadrotor control in a complex obstacle field
demonstrate the validity of the proposed method.Comment: arXiv admin note: text overlap with arXiv:1510.0534
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