11,371 research outputs found
Simpler is better: a novel genetic algorithm to induce compact multi-label chain classifiers
Multi-label classification (MLC) is the task of assigning multiple class labels to an object based on the features that describe the object. One of the most effective MLC methods is known as Classifier Chains (CC). This approach consists in training q binary classifiers linked in a chain, y1 → y2 → ... → yq, with each responsible for classifying a specific label in {l1, l2, ..., lq}. The chaining mechanism allows each individual classifier to incorporate the predictions of the previous ones as additional information at classification time. Thus, possible correlations among labels can be automatically exploited. Nevertheless, CC suffers from two important drawbacks: (i) the label ordering is decided at random, although it usually has a strong effect on predictive accuracy; (ii) all labels are inserted into the chain, although some of them might carry irrelevant information to discriminate the others. In this paper we tackle both problems at once, by proposing a novel genetic algorithm capable of searching for a single optimized label ordering, while at the same time taking into consideration the utilization of partial chains. Experiments on benchmark datasets demonstrate that our approach is able to produce models that are both simpler and more accurate
The 3-Loop Non-Singlet Heavy Flavor Contributions to the Structure Function g_1(x,Q^2) at Large Momentum Transfer
We calculate the massive flavor non-singlet Wilson coefficient for the heavy
flavor contributions to the polarized structure function in the
asymptotic region to 3-loop order in Quantum Chromodynamics at
general values of the Mellin variable and the momentum fraction , and
derive heavy flavor corrections to the Bjorken sum-rule. Numerical results are
presented for the charm quark contribution. Results on the structure function
in the twist-2 approximation are also given.Comment: 29 pages, 8 Figure
Scalar Top Quark Studies with Various Visible Energies
The precision determination of scalar top quark properties will play an
important role at a future International Linear Collider (ILC). Recent and
ongoing studies are discussed for different experimental topologies in the
detector. First results are presented for small mass differences between the
scalar top and neutralino masses. This corresponds to a small expected visible
energy in the detector. An ILC will be a unique accelerator to explore this
scenario. In addition to finding the existence of light stop quarks, the
precise measurement of their properties is crucial for testing their impact on
the dark matter relic abundance and the mechanism of electroweak baryogenesis.
Significant sensitivity for mass differences down to 5 GeV are obtained. The
simulation is based on a fast and realistic detector simulation. A vertex
detector concept of the Linear Collider Flavor Identification
(LCFI)collaboration, which studies pixel detectors for heavy quark flavour
identification, is implemented in the simulations for c-quark tagging. The
study extends simulations for large mass differences (large visible energy) for
which aspects of different detector simulations, the vertex detector design,
and different methods for the determination of the scalar top mass are
discussed. Based on the detailed simulations we study the uncertainties for the
dark matter density predictions and their estimated uncertainties from various
sources. In the region of parameters where stop-neutralino co-annihilation
leads to a value of the relic density consistent with experimental results, as
precisely determined by the Wilkinson Microwave Anisotropy Probe (WMAP), the
stop-neutralino mass difference is small and the ILC will be able to explore
this region efficiently.Comment: 11 pages, 11 figures, presented at SUSY'0
The unpolarized two-loop massive pure singlet Wilson coefficients for deep-inelastic scattering
We calculate the massive two--loop pure singlet Wilson coefficients for heavy
quark production in the unpolarized case analytically in the whole kinematic
region and derive the threshold and asymptotic expansions. We also recalculate
the corresponding massless two--loop Wilson coefficients. The complete
expressions contain iterated integrals with elliptic letters. The contributing
alphabets enlarge the Kummer-Poincar\'e letters by a series of square-root
valued letters. A new class of iterated integrals, the Kummer-elliptic
integrals, are introduced. For the structure functions and we also
derive improved asymptotic representations adding power corrections. Numerical
results are presented.Comment: 42, pages Latex, 8 Figure
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