Toward the theory of ring Q-homeomophisms

We investigate classes of the so-called ring Q-homeomorphisms including, in particular, Q-homeomorphisms, various classes of homeomorphisms with finite length distortion, Sobolev’s classes etc. In terms of the majorant Q(x), we give a series of criteria for normality based on estimates of the distortion of the spherical distance under ring Q-homeomorphisms. In particular, it is shown that the class of all ring Q-homeomorphisms f of a domain D ⊂ ℝ ⁿ into , n ≥ 2, with , forms a normal family, if Q(x) has finite mean oscillation in D. We also prove normality of , for instance, if Q(x) has singularities of logarithmic type whose degrees are not greater than n − 1 at every point x ∈ D. The results are applicable, in particular, to mappings with finite length distortion and Sobolev’s classes.     

Toward the classification of biangular harmonic frames

Equiangular tight frames (ETFs) and biangular tight frames (BTFs) – sets of unit vectors with basis-like properties whose pairwise absolute inner products admit exactly one or two values, respectively – are useful for many applications. A well-understood class of ETFs are those which manifest as harmonic frames – vector sets defined in terms of the characters of finite abelian groups – because they are characterized by combinatorial objects called difference sets.This work is dedicated to the study of the underlying combinatorial structures of harmonic BTFs. We show that if a harmonic frame is generated by a divisible difference set, a partial difference set or by a special structure with certain Gauss summing properties – all three of which are generalizations of difference sets that fall under the umbrella term “bidifference set” – then it is either a BTF or an ETF. However, we also show that the relationship between harmonic BTFs and bidifference sets is not as straightforward as the correspondence between harmonic ETFs and difference sets, as there are examples of bidifference sets that do not generate harmonic BTFs. In addition, we study another class of combinatorial structures, the nested divisible difference sets, which yields an example of a harmonic BTF that is not generated by a bidifference set.     

Toward a Clarity of the Extreme Value Theorem

We apply a framework developed by C. S. Peirce to analyze the concept of clarity, so as to examine a pair of rival mathematical approaches to a typical result in analysis. Namely, we compare an intuitionist and an infinitesimal approaches to the extreme value theorem. We argue that a given pre-mathematical phenomenon may have several aspects that are not necessarily captured by a single formalisation, pointing to a complementarity rather than a rivalry of the approaches.     

Toward the Routine Analysis of Diverse Data Types

This article describes a variety of data analysis problems. The types of data across these problems included free text, parallel text, an image collection, remote sensing imagery, and network packets. A strategy for approaching the analysis of these diverse types of data is described. A key part of the challenge is mapping the analytic results back into the original domain and data setting. Additionally, a common computational bottleneck encountered in each of these problems is diagnosed as analysis tools and algorithms with unbounded memory characteristics. This experience and the analysis suggest a research and development path that could greatly extend the scale of problems that can be addressed with routine data analysis tools. In particular, there are opportunities associated with developing theory and functioning algorithms with favorable memory-usage characteristics, and there are opportunities associated with developing methods and theory for describing the outcomes of analyses for the various types of data.     

Toward an arithmetic of polynomials

Summary ForR a commutative ring, which may have divisors of zero but which has no idempotents other than zero and one, we consider the problem of unique factorization of a polynomial with coefficients inR. We prove that, if the polynomial is separable, then such a unique factorization exists. We also define a Legendre symbol for a separable polynomial and a prime of commutative ring with exactly two idempotents in such a way that the symbols of classical number theory are subsumed. We calculate this symbol forR = Q in two cases where it has classically been of interest, namely quadratic extensions and cyclotomic extensions. We then calculate it in a situation which is new, namely the so called generalized cyclotomic extensions from a paper by S. Beale and D. K. Harrison. We study the Galois theory in the general ring situation and in particular define a category of separable polynomials (this is an extension of a paper by D. K. Harrison and M. Vitulli) and a cohomology theory of separable polynomials.     

Toward a theorem of douady

A theorem of Douady says that the absolute Galois group of a rational function field F(x) in one variable over an algebraically closed field F of characteristic 0 is a free profinite group. A new method is proposed to extend Douady’s theorem from the case of the complex number field F = ℂ to the case of an arbitrary field.     

Toward a possible solution of the generalized continuum problem

A natural property of finite sets is extrapolated to the infinite and is couched in terms of the ABS-axiom in the language of ZF. It is shown that the generalized continuum hypothesis enters the picture of ZF+ABS-theory. Translated fromAlgebra i Logika, Vol. 38, No. 4, pp. 409–418, July–August, 1999.     

Toward Improving the Mathematics Preparation of Elementary Preservice Teachers

Research suggests the importance of mathematics knowledge for teaching (MKT) for enabling elementary school teachers to effectively teach mathematics. MKT involves both mathematical content knowledge (M‐CK) and mathematical pedagogical content knowledge (M‐PCK). However, there is no consensus on how best to prepare elementary preservice teachers (PSTs) to achieve M‐CK and M‐PCK. This study builds on research related to MKT by investigating influences of mathematics content courses designed specifically for elementary PSTs (IMPACT courses—Impact of Mathematics Pedagogy and Content on Teaching) on their attitudes (i.e., confidence and motivation) toward M‐CK and M‐PCK. Results suggest that the PSTs who participated in these IMPACT courses not only acquired high levels of confidence and motivation toward M‐CK, but also showed significant and greater gains in attitudes toward M‐PCK, after taking the required mathematics methods course, than their counterparts. Further, the findings suggest that these IMPACT courses provided a mathematical foundation that allowed the PSTs to engage in mathematics teaching methods better than those PSTs who did not have such a foundation. These results suggest potential course experiences that may enhance M‐CK and M‐PCK for elementary PSTs.     

Toward the rank-one singular perturbation theory of self-adjoint operators

The perturbation theory is developed for the case where an arbitrary positive self-adjoint operator is perturbed by the projector on a generalized vector. Similar to the well-known problem –+, we obtain, in the general case, explicit representations for singularly perturbed operators and their resolvents, and we find the point spectrum and an explicit form of the corresponding eigenvectors. Our approach differs from the usual ones and is based on the self-adjoint extension theory of semibounded operators.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 11, pp. 1559–1566, November, 1991.     

Toward equivariant Iwasawa theory

 Let l be an odd prime number, K/k a finite Galois extension of totally real number fields, and G _∞ , X _∞ the Galois groups of K _∞ /k and M _∞ /K _∞ , respectively, where K _∞ is the cyclotomic l-extension of K and M _∞ the maximal abelian S-ramified l-extension of K _∞ with S a sufficiently large finite set of primes of k. We introduce a new K-theoretic variant of the Iwasawa ℤ[[G _∞ ]]-module X _∞ and, for K/k abelian, formulate a conjecture, which is the main conjecture of classical Iwasawa theory when lł[K : k]. We prove this new conjecture when Iwasawa's μ-invariant vanishes and discuss consequences for the Lifted Root Number Conjecture at l. Received: 7 August 2001 / Revised version: 6 May 2002 We acknowledge financial support provided by NSERC. Mathematics Subject Classification (2000): 11R23, 11R27, 11R32, 11R33, 11R37, 11R42, 11S20, 11S23, 11S31, 11S40     

Toward an Elementary Axiomatic Theory of the Category of LP-Matroids

The purpose of this paper is to provide the beginnings of an elementary theory for the category of loopless pointed matroids and strong maps. We propose a finite set of elementary axioms that is the beginning of an elementary axiomatic theory for this category.