30,923 research outputs found
The descriptive theory of represented spaces
This is a survey on the ongoing development of a descriptive theory of
represented spaces, which is intended as an extension of both classical and
effective descriptive set theory to deal with both sets and functions between
represented spaces. Most material is from work-in-progress, and thus there may
be a stronger focus on projects involving the author than an objective survey
would merit.Comment: survey of work-in-progres
An intelligent assistant for exploratory data analysis
In this paper we present an account of the main features of SNOUT, an intelligent assistant for exploratory data analysis (EDA) of social science survey data that incorporates a range of data mining techniques. EDA has much in common with existing data mining techniques: its main objective is to help an investigator reach an understanding of the important relationships ina data set rather than simply develop predictive models for selectd variables. Brief descriptions of a number of novel techniques developed for use in SNOUT are presented. These include heuristic variable level inference and classification, automatic category formation, the use of similarity trees to identify groups of related variables, interactive decision tree construction and model selection using a genetic algorithm
Complexity of weakly null sequences
We introduce an ordinal index which measures the complexity of a weakly null
sequence, and show that a construction due to J. Schreier can be iterated to
produce for each alpha < omega_1, a weakly null sequence (x^{alpha}_n)_n in
C(omega^{omega^{alpha}})) with complexity alpha. As in the Schreier example
each of these is a sequence of indicator functions which is a suppression-1
unconditional basic sequence. These sequences are used to construct
Tsirelson-like spaces of large index. We also show that this new ordinal index
is related to the Lavrentiev index of a Baire-1 function and use the index to
sharpen some results of Alspach and Odell on averaging weakly null sequences
Zeno's Paradoxes. A Cardinal Problem 1. On Zenonian Plurality
In this paper the claim that Zeno's paradoxes have been solved is contested.
Although no one has ever touched Zeno without refuting him (Whitehead), it will
be our aim to show that, whatever it was that was refuted, it was certainly not
Zeno. The paper is organised in two parts. In the first part we will
demonstrate that upon direct analysis of the Greek sources, an underlying
structure common to both the Paradoxes of Plurality and the Paradoxes of Motion
can be exposed. This structure bears on a correct - Zenonian - interpretation
of the concept of division through and through. The key feature, generally
overlooked but essential to a correct understanding of all his arguments, is
that they do not presuppose time. Division takes place simultaneously. This
holds true for both PP and PM. In the second part a mathematical representation
will be set up that catches this common structure, hence the essence of all
Zeno's arguments, however without refuting them. Its central tenet is an
aequivalence proof for Zeno's procedure and Cantor's Continuum Hypothesis. Some
number theoretic and geometric implications will be shortly discussed.
Furthermore, it will be shown how the Received View on the motion-arguments can
easely be derived by the introduction of time as a (non-Zenonian) premiss, thus
causing their collapse into arguments which can be approached and refuted by
Aristotle's limit-like concept of the potentially infinite, which remained -
though in different disguises - at the core of the refutational strategies that
have been in use up to the present. Finally, an interesting link to Newtonian
mechanics via Cremona geometry can be established.Comment: 41 pages, 7 figure
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