443 research outputs found
Strings and Branes in Nonabelian Gauge Theory
It is an old speculation that SU(N) gauge theory can alternatively be
formulated as a string theory. Recently this subject has been revived, in the
wake of the discovery of D-branes. In particular, it has been argued that at
least some conformally invariant cousins of the theory have such a string
representation. This is a pedagogical introduction to these developments for
non-string theorists. Some of the existing arguments are simplified.Comment: Reference adde
Evaluating Two-Stream CNN for Video Classification
Videos contain very rich semantic information. Traditional hand-crafted
features are known to be inadequate in analyzing complex video semantics.
Inspired by the huge success of the deep learning methods in analyzing image,
audio and text data, significant efforts are recently being devoted to the
design of deep nets for video analytics. Among the many practical needs,
classifying videos (or video clips) based on their major semantic categories
(e.g., "skiing") is useful in many applications. In this paper, we conduct an
in-depth study to investigate important implementation options that may affect
the performance of deep nets on video classification. Our evaluations are
conducted on top of a recent two-stream convolutional neural network (CNN)
pipeline, which uses both static frames and motion optical flows, and has
demonstrated competitive performance against the state-of-the-art methods. In
order to gain insights and to arrive at a practical guideline, many important
options are studied, including network architectures, model fusion, learning
parameters and the final prediction methods. Based on the evaluations, very
competitive results are attained on two popular video classification
benchmarks. We hope that the discussions and conclusions from this work can
help researchers in related fields to quickly set up a good basis for further
investigations along this very promising direction.Comment: ACM ICMR'1
Towards Contextual Action Recognition and Target Localization with Active Allocation of Attention
Exploratory gaze movements are fundamental for gathering the most relevant information regarding the partner during social interactions. We have designed and implemented a system for dynamic attention allocation which is able to actively control gaze movements during a visual action recognition task. During the observation of a partners reaching movement, the robot is able to contextually estimate the goal position of the partner hand and the location in space of the candidate targets, while moving its gaze around with the purpose of optimizing the gathering of information relevant for the task. Experimental results on a simulated environment show that active gaze control provides a relevant advantage with respect to typical passive observation, both in term of estimation precision and of time required for action recognition. © 2012 Springer-Verlag
D-brane Wess--Zumino actions, T-duality and the cosmological constant
A geometrical formulation of the T-duality rules for type II superstring
Ramond--Ramond fields is presented. This is used to derive the Wess-Zumino
terms in superstring D-brane actions, including terms proportional to the mass
parameter of the IIA theory, thereby completing partial results in the
literature. For non-abelian world-volume gauge groups the massive type IIA
D-brane actions contain non-abelian Chern--Simons terms for the Born--Infeld
gauge potential, implying a quantization of the IIA cosmological constant.Comment: Version to be published in Physics Letters (minor corrections
Meta-Tracker: Fast and Robust Online Adaptation for Visual Object Trackers
This paper improves state-of-the-art visual object trackers that use online
adaptation. Our core contribution is an offline meta-learning-based method to
adjust the initial deep networks used in online adaptation-based tracking. The
meta learning is driven by the goal of deep networks that can quickly be
adapted to robustly model a particular target in future frames. Ideally the
resulting models focus on features that are useful for future frames, and avoid
overfitting to background clutter, small parts of the target, or noise. By
enforcing a small number of update iterations during meta-learning, the
resulting networks train significantly faster. We demonstrate this approach on
top of the high performance tracking approaches: tracking-by-detection based
MDNet and the correlation based CREST. Experimental results on standard
benchmarks, OTB2015 and VOT2016, show that our meta-learned versions of both
trackers improve speed, accuracy, and robustness.Comment: Code: https://github.com/silverbottlep/meta_tracker
Correlation Functions in Matrix Models Modified by Wormhole Terms
We calculate correlation functions in matrix models modified by trace-squared
terms. First we study scaling operators in modified one-matrix models and find
that their correlation functions satisfy modified Virasoro constraints. Then we
turn to dressed order parameters in minimal models and show that their
correlators satisfy Goulian-Li formulae continued to negative Liouville
dressing exponents. Our calculations provide additional support for the idea
that the modified matrix models contain operators with the negative branch of
gravitational dressing.Comment: 24 pages, epsf.st
CP^{N-1} models and the Quantized 2D Black Holes
We have examined the coupled system of the dilaton gravity and the
theory known as a model of the confinement of massive scalar quarks. After the
quantization of the system, we could see the quantum effect of the gravitation
on the coupling constant of model and how the coupling constant of
dynamically induced gauge field changes near the black hole configuration.Comment: 12 pages, Late
BPS mass spectrum from D-brane action
We derive the BPS mass formulae of the Dirichlet branes from the Born-Infeld
type action. BPS saturation is realized when the brane has the minimal volume
while keeping the appropriate winding numbers. We apply the idea to two cases,
type IIA superstring compactified on and . The result is consistent
with the string duality, and the expected spectrum for the BPS states is
reproduced.Comment: 11 pages, latex, no figur
D-brane Solitons in Supersymmetric Sigma-Models
Massive D=4 N=2 supersymmetric sigma models typically admit domain wall
(Q-kink) solutions and string (Q-lump) solutions, both preserving 1/2
supersymmetry. We exhibit a new static 1/4 supersymmetric `kink-lump' solution
in which a string ends on a wall, and show that it has an effective realization
as a BIon of the D=4 super DBI-action. It is also shown to have a
time-dependent Q-kink-lump generalization which reduces to the Q-lump in a
limit corresponding to infinite BI magnetic field. All these 1/4 supersymmetric
sigma-model solitons are shown to be realized in M-theory as calibrated, or
`Q-calibrated', M5-branes in an M-monopole background.Comment: 16 pages, 3 figures, Late
- âŠ