20,985 research outputs found
Neural Discourse Structure for Text Categorization
We show that discourse structure, as defined by Rhetorical Structure Theory
and provided by an existing discourse parser, benefits text categorization. Our
approach uses a recursive neural network and a newly proposed attention
mechanism to compute a representation of the text that focuses on salient
content, from the perspective of both RST and the task. Experiments consider
variants of the approach and illustrate its strengths and weaknesses.Comment: ACL 2017 camera ready versio
Dynamic Entity Representations in Neural Language Models
Understanding a long document requires tracking how entities are introduced
and evolve over time. We present a new type of language model, EntityNLM, that
can explicitly model entities, dynamically update their representations, and
contextually generate their mentions. Our model is generative and flexible; it
can model an arbitrary number of entities in context while generating each
entity mention at an arbitrary length. In addition, it can be used for several
different tasks such as language modeling, coreference resolution, and entity
prediction. Experimental results with all these tasks demonstrate that our
model consistently outperforms strong baselines and prior work.Comment: EMNLP 2017 camera-ready versio
Estimating the mass of the debris disc in HD 69830
We present a method to estimate the mass of the debris disc in the HD 69830
system, which also hosts three exoplanets with Neptune-like minimum masses. By
considering the range of published stellar ages, we interpret the infrared
emission from the debris disc as originating from a steady state, collisional
cascade of dust grains. Using dynamical survival models subjected to
observational constraints, we estimate the allowed range of disc masses. If the
disc has an age of about 1 Gyr, then its mass is several times that of our
asteroid belt. The maximum allowed age for the disc and the number of
planetesimals it contains are determined by the assumed value for the binding
energy of the planetesimals. If one insists on interpreting the disc as being
transient, then this mass estimate becomes an upper limit.Comment: Accepted by MNRAS. 4 pages, 2 figures. No changes from previous
version, except for corrections of typographical errors and to British
English (e.g., "disc"
Single Transverse Spin Asymmetry for Large-p_T Pion Production in Semi-Inclusive Deep Inelastic Scattering
We study the single spin asymmetry (SSA) for the pion production with large
transverse momentum p_T in semi-inclusive deep inelastic scattering
. We derive the twist-3 cross section formula for SSA,
focussing on the soft-gluon-pole contributions associated with the twist-3
distribution for the nucleon and with the twist-3 fragmentation function for
the pion. We present a simple estimate of the asymmetries due to each twist-3
effect from nucleon and pion, respectively, by fixing the overall strength of
the relevant nonperturbative quantities by the data on the SSA A_N in
collision.Comment: 19 pages in LaTex. Some discussions added. To appear in Nucl. Phys.
Technologies for imaging neural activity in large volumes
Neural circuitry has evolved to form distributed networks that act dynamically across large volumes. Collecting data from individual planes, conventional microscopy cannot sample circuitry across large volumes at the temporal resolution relevant to neural circuit function and behaviors. Here, we review emerging technologies for rapid volume imaging of neural circuitry. We focus on two critical challenges: the inertia of optical systems, which limits image speed, and aberrations, which restrict the image volume. Optical sampling time must be long enough to ensure high-fidelity measurements, but optimized sampling strategies and point spread function engineering can facilitate rapid volume imaging of neural activity within this constraint. We also discuss new computational strategies for the processing and analysis of volume imaging data of increasing size and complexity. Together, optical and computational advances are providing a broader view of neural circuit dynamics, and help elucidate how brain regions work in concert to support behavior
Twist-3 Formalism for Single Transverse Spin Asymmetry Reexamined: Semi-Inclusive Deep Inelastic Scattering
We study the single spin asymmetry (SSA) for the pion production in
semi-inclusive deep inelastic scattering, , in the
framework of the collinear factorization. We derive the complete cross section
formula associated with the twist-3 quark-gluon correlation functions for the
transversely polarized nucleon, including all types of pole (hard-pole,
soft-fermion-pole and soft-gluon-pole) contributions which produce the strong
interaction phase necessary for SSA. We prove that the partonic hard part from
each pole contribution satisfies certain constraints from Ward identities for
color gauge invariance. We demonstrate that the use of these new constraints is
crucial to reorganize the collinear expansion of the Feynman diagrams into
manifestly gauge-invariant form so as to obtain the factorization formula for
the cross section in terms of a complete set of the twist-3 distributions
without any double counting. It also provides a simpler method for the actual
calculation. We also present a simple estimate of SSA based on our cross
section formula, using a model for the ``soft-gluon-pole function'' that
represents the relevant twist-3 quark-gluon correlation, and compare the
magnitude of the terms involving the derivative of the soft-gluon-pole function
with that of the ``non-derivative'' terms.Comment: 38 pages, 11 figures. Final version, to appear in Nucl. Phys.
Found: High Surface Brightness Compact Galaxies
We are using the 2dF spectrograph to make a survey of all objects (`stars'
and `galaxies') in a 12 sq.deg region towards the Fornax cluster. We have
discovered a population of compact emission-line galaxies unresolved on
photographic sky survey plates and therefore missing in most galaxy surveys
based on such material. These galaxies are as luminous as normal field
galaxies. Using H-alpha to estimate star formation they contribute at least an
additional 5 per cent to the local star formation rate.Comment: To appear in "The Low Surface Brightness Universe", IAU Coll 171,
eds. J.I. Davies et al., A.S.P. Conference Series. 3 pages, LaTex, 1
encapsulated ps-figure, requires paspconf.st
Decentralized Multi-Armed Bandit Can Outperform Classic Upper Confidence Bound
This paper studies a decentralized multi-armed bandit problem in a
multi-agent network. The problem is simultaneously solved by N agents assuming
they face a common set of M arms and share the same mean of each arm's reward.
Each agent can receive information only from its neighbors, where the neighbor
relations among the agents are described by a directed graph whose vertices
represent agents and whose directed edges depict neighbor relations. A fully
decentralized multi-armed bandit algorithm is proposed for each agent, which
twists the classic consensus algorithm and upper confidence bound (UCB)
algorithm. It is shown that the algorithm guarantees each agent to achieve a
better logarithmic asymptotic regret than the classic UCB provided the neighbor
graph is strongly connected. The regret can be further improved if the neighbor
graph is undirected
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