11,825 research outputs found
The String Light Cone in the pp-wave Background
In this letter, we determine the particle and the string light cone in the
pp-wave background. The result is a deformed version of the flat one. We point
out the light cone exhibits an intriguing periodicity in the light cone time
direction x^+ with a period \sim 1/ \mu. Our results also suggest that a
quantum theory in the pp-wave background can be formulated consistently only if
the background is periodic in the light cone time x^+.Comment: 10 pages. v2: references and comments adde
Majorana Fermions on Zigzag Edge of Monolayer Transition Metal Dichalcogenides
Majorana fermions, quantum particles with non-Abelian exchange statistics,
are not only of fundamental importance, but also building blocks for
fault-tolerant quantum computation. Although certain experimental breakthroughs
for observing Majorana fermions have been made recently, their conclusive
dection is still challenging due to the lack of proper material properties of
the underlined experimental systems. Here we propose a new platform for
Majorana fermions based on edge states of certain non-topological
two-dimensional semiconductors with strong spin-orbit coupling, such as
monolayer group-VI transition metal dichalcogenides (TMD). Using
first-principles calculations and tight-binding modeling, we show that zigzag
edges of monolayer TMD can host well isolated single edge band with strong
spin-orbit coupling energy. Combining with proximity induced s-wave
superconductivity and in-plane magnetic fields, the zigzag edge supports robust
topological Majorana bound states at the edge ends, although the
two-dimensional bulk itself is non-topological. Our findings points to a
controllable and integrable platform for searching and manipulating Majorana
fermions.Comment: 12 pages, 7 figure
Learning Compact Recurrent Neural Networks with Block-Term Tensor Decomposition
Recurrent Neural Networks (RNNs) are powerful sequence modeling tools.
However, when dealing with high dimensional inputs, the training of RNNs
becomes computational expensive due to the large number of model parameters.
This hinders RNNs from solving many important computer vision tasks, such as
Action Recognition in Videos and Image Captioning. To overcome this problem, we
propose a compact and flexible structure, namely Block-Term tensor
decomposition, which greatly reduces the parameters of RNNs and improves their
training efficiency. Compared with alternative low-rank approximations, such as
tensor-train RNN (TT-RNN), our method, Block-Term RNN (BT-RNN), is not only
more concise (when using the same rank), but also able to attain a better
approximation to the original RNNs with much fewer parameters. On three
challenging tasks, including Action Recognition in Videos, Image Captioning and
Image Generation, BT-RNN outperforms TT-RNN and the standard RNN in terms of
both prediction accuracy and convergence rate. Specifically, BT-LSTM utilizes
17,388 times fewer parameters than the standard LSTM to achieve an accuracy
improvement over 15.6\% in the Action Recognition task on the UCF11 dataset.Comment: CVPR201
O(a) Perturbative improvement for Wilson fermions
The coefficient of the O(a)-improved
Sheikholeslami-Wohlert action for Wilson fermions are perturbatively
determined at one-loop level and estimated at two-loop level.Comment: 8-pages + (two pages of Fig.s) MPI-ph/93-2
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