52,686 research outputs found
PRESISTANT: Learning based assistant for data pre-processing
Data pre-processing is one of the most time consuming and relevant steps in a
data analysis process (e.g., classification task). A given data pre-processing
operator (e.g., transformation) can have positive, negative or zero impact on
the final result of the analysis. Expert users have the required knowledge to
find the right pre-processing operators. However, when it comes to non-experts,
they are overwhelmed by the amount of pre-processing operators and it is
challenging for them to find operators that would positively impact their
analysis (e.g., increase the predictive accuracy of a classifier). Existing
solutions either assume that users have expert knowledge, or they recommend
pre-processing operators that are only "syntactically" applicable to a dataset,
without taking into account their impact on the final analysis. In this work,
we aim at providing assistance to non-expert users by recommending data
pre-processing operators that are ranked according to their impact on the final
analysis. We developed a tool PRESISTANT, that uses Random Forests to learn the
impact of pre-processing operators on the performance (e.g., predictive
accuracy) of 5 different classification algorithms, such as J48, Naive Bayes,
PART, Logistic Regression, and Nearest Neighbor. Extensive evaluations on the
recommendations provided by our tool, show that PRESISTANT can effectively help
non-experts in order to achieve improved results in their analytical tasks
Coset Realization of Unifying W-Algebras
We construct several quantum coset W-algebras, e.g. sl(2,R)/U(1) and
sl(2,R)+sl(2,R) / sl(2,R), and argue that they are finitely nonfreely
generated. Furthermore, we discuss in detail their role as unifying W-algebras
of Casimir W-algebras. We show that it is possible to give coset realizations
of various types of unifying W-algebras, e.g. the diagonal cosets based on the
symplectic Lie algebras sp(2n) realize the unifying W-algebras which have
previously been introduced as `WD_{-n}'. In addition, minimal models of WD_{-n}
are studied. The coset realizations provide a generalization of
level-rank-duality of dual coset pairs. As further examples of finitely
nonfreely generated quantum W-algebras we discuss orbifolding of W-algebras
which on the quantum level has different properties than in the classical case.
We demonstrate in some examples that the classical limit according to Bowcock
and Watts of these nonfreely finitely generated quantum W-algebras probably
yields infinitely nonfreely generated classical W-algebras.Comment: 60 pages (plain TeX) (final version to appear in Int. J. Mod. Phys.
A; several minor improvements and corrections - for details see beginning of
file
Searching for Dark Matter in the CMB: A Compact Parameterization of Energy Injection from New Physics
High-precision measurements of the temperature and polarization anisotropies
of the cosmic microwave background radiation have been previously employed to
set robust constraints on dark matter annihilation during recombination. In
this work we improve and generalize these constraints to apply to energy
deposition during the recombination era with arbitrary redshift dependence. Our
approach also provides more rigorous and model-independent bounds on dark
matter annihilation and decay scenarios. We employ principal component analysis
to identify a basis of weighting functions for the energy deposition. The
coefficients of these weighting functions parameterize any energy deposition
model and can be constrained directly by experiment. For generic energy
deposition histories that are currently allowed by WMAP7 data, up to 3
principal component coefficients are measurable by Planck and up to 5
coefficients are measurable by an ideal cosmic variance limited experiment. For
WIMP dark matter, our analysis demonstrates that the effect on the CMB is
described well by a single (normalization) parameter and a "universal" redshift
dependence for the energy deposition history. We give WMAP 7 constraints on
both generic energy deposition histories and the universal WIMP case.Comment: 30 pages, 24 figure
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