3,048 research outputs found
Potential Theory on Trees, Graphs and Ahlfors Regular Metric Spaces
We investigate connections between potential theories on a Ahlfors-regular
metric space X, on a graph G associated with X, and on the tree T obtained by
removing the "horizontal edges" in G. Applications to the calculation of set
capacity are given.Comment: 45 pages; presentation improved based on referee comment
Information Extraction in Illicit Domains
Extracting useful entities and attribute values from illicit domains such as
human trafficking is a challenging problem with the potential for widespread
social impact. Such domains employ atypical language models, have `long tails'
and suffer from the problem of concept drift. In this paper, we propose a
lightweight, feature-agnostic Information Extraction (IE) paradigm specifically
designed for such domains. Our approach uses raw, unlabeled text from an
initial corpus, and a few (12-120) seed annotations per domain-specific
attribute, to learn robust IE models for unobserved pages and websites.
Empirically, we demonstrate that our approach can outperform feature-centric
Conditional Random Field baselines by over 18\% F-Measure on five annotated
sets of real-world human trafficking datasets in both low-supervision and
high-supervision settings. We also show that our approach is demonstrably
robust to concept drift, and can be efficiently bootstrapped even in a serial
computing environment.Comment: 10 pages, ACM WWW 201
Signals of CP Violation Beyond the MSSM in Higgs and Flavor Physics
We study an extension of the Higgs sector of the Minimal Supersymmetric
Standard Model (MSSM), considering the effects of new degrees of freedom at the
TeV scale, and allowing for sources of CP violation beyond the MSSM (BMSSM). We
analyze the impact of the BMSSM sources of CP violation on the Higgs collider
phenomenology and on low energy flavor and CP violating observables. We
identify distinct Higgs collider signatures that cannot be realized, either in
the case without CP violating phases or in the CP violating MSSM, and
investigate the prospects to probe them at the Tevatron and the LHC. The most
striking benchmark scenario has three neutral Higgs bosons that all decay
dominantly into W boson pairs and that are well within the reach of the 7 TeV
LHC run. On the other hand, we also present scenarios with three Higgs bosons
that have masses M_Hi > 150 GeV and decay dominantly into b bbar. Such
scenarios are much more challenging to probe and can even lie completely
outside the reach of the 7 TeV LHC run. We explore complementary scenarios with
standard MSSM Higgs signals that allow to accommodate a sizable B_s mixing
phase as indicated by D0, as well as the excess in B_s --> mu+ mu- candidates
recently reported by CDF. We find that, in contrast to the MSSM, a minimal
flavor violating soft sector is sufficient to generate significant corrections
to CP violating observables in meson mixing, compatible with EDM constraints.
In particular, a sizable B_s mixing phase, S_psiphi < 0.4, can be achieved for
specific regions of parameter space. Such a large B_s mixing phase would
unambiguously imply a sizable suppression of S_psiKs with respect to the SM
prediction and a BR(B_s --> mu+ mu-) close to the 95% C.L. upper bound reported
by CDF.Comment: 58 pages, 15 figures, 2 tables, v2 matches published versio
Besov Space, Schatten Classes And Commutators Of Riesz Transforms Associated With The Neumann Laplacian
This article provides a deeper study of the Riesz transform commutators
associated with the Neumann Laplacian operator on .
Along the line of singular value estimates for Riesz transform commutators
established by Janson--Wolff and Rochberg--Semmes, we establish a full range of
Schatten- class characterization for these commutators
The Rotation Average in Lightcone Time-Ordered Perturbation Theory
We present a rotation average of the two-body scattering amplitude in the
lightcone time()-ordered perturbation theory. Using a rotation average
procedure, we show that the contribution of individual time-ordered diagram can
be quantified in a Lorentz invariant way. The number of time-ordered diagrams
can also be reduced by half if the masses of two bodies are same. In the
numerical example of theory, we find that the higher Fock-state
contribution is quite small in the lightcone quantization.Comment: 25 pages, REVTeX, epsf.sty, 69 eps file
Relativistic Quantum Mechanics - Particle Production and Cluster Properties
This paper constructs relativistic quantum mechanical models of particles
satisfying cluster properties and the spectral condition which do not conserve
particle number. The treatment of particle production is limited to systems
with a bounded number of bare-particle degrees of freedom. The focus of this
paper is about the realization of cluster properties in these theories.Comment: 36 pages, Late
Study of relativistic bound states for scalar theories in Bethe-Salpeter and Dyson-Schwinger formalism
The Bethe-Salpeter equation for Wick-Cutkosky like models is solved in
dressed ladder approximation. The bare vertex truncation of the Dyson-Schwinger
equations for propagators is combined with the dressed ladder Bethe-Salpeter
equation for the scalar S-wave bound state amplitudes. With the help of
spectral representation the results are obtained directly in Minkowski space.
We give a new analytic formula for the resulting equation simplifying the
numerical treatment. The bare ladder approximation of Bethe-Salpeter equation
is compared with the one with dressed ladder. The elastic electromagnetic form
factors is calculated within the relativistic impulse approximation.Comment: 30 pages, 10 figures, accepted for publication in Phys. Rev.
Neurogenesis Drives Stimulus Decorrelation in a Model of the Olfactory Bulb
The reshaping and decorrelation of similar activity patterns by neuronal
networks can enhance their discriminability, storage, and retrieval. How can
such networks learn to decorrelate new complex patterns, as they arise in the
olfactory system? Using a computational network model for the dominant neural
populations of the olfactory bulb we show that fundamental aspects of the adult
neurogenesis observed in the olfactory bulb -- the persistent addition of new
inhibitory granule cells to the network, their activity-dependent survival, and
the reciprocal character of their synapses with the principal mitral cells --
are sufficient to restructure the network and to alter its encoding of odor
stimuli adaptively so as to reduce the correlations between the bulbar
representations of similar stimuli. The decorrelation is quite robust with
respect to various types of perturbations of the reciprocity. The model
parsimoniously captures the experimentally observed role of neurogenesis in
perceptual learning and the enhanced response of young granule cells to novel
stimuli. Moreover, it makes specific predictions for the type of odor
enrichment that should be effective in enhancing the ability of animals to
discriminate similar odor mixtures
Heavy quark supermultiplet excitations
Lorentz covariant wave functions for meson and baryon supermultiplets are
simply derived by boosting representations corresponding to
multiquark systems at rest.Comment: 12 pages (Revtex), UTAS-PHYS-93-4
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