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Let where a0≠0, m≥2, n = e1 + … + em and the ξi(1≤i≤m) are the distinct zeros of f in some algebraic closure of the p-adic field . Then K = (ξ1, ξ2, …, ξm) is a finite separable extension of and we denote by “ord” the unique extension of the (additive) p-adic valuation on to K, normalized with ord p = 1.
A convex compact subset of ℝd is called a convex body. The (Euclidean) surface area and volume of a convex body K are denoted s(K) and v(K) respectively. The support function of a convex body K is denned by h(K, x) = maxy∈K xty and the polar dual of K is given by K0 = {x: |xty|1, y∈K}. Double vertical bars shall denote the Euclidean length of a vector , and S shall denote the unit sphere (the Euclidean unit ball): S = {x: ║x║≤1}. We use for the mixed volume
Atkinson, Young and Brezovich [1: 1983] gave a formula for the potential distribution due to a circular disc condenser with arbitrary spacing parameter к (the ratio of separation of the discs to their radius). This was simpler to calculate than the formulation which I gave in [8: 1949]; but unfortunately it fails to satisfy two requirements, as the present paper shows. Together with [8], this paper shows that the potential formulated in [8] satisfies all requirements.
Nous estimons le module des sommes trigonométriques sur la variété de dimension n – s definie par s formes en n variables, avec une forme linéaire en exposant. Cela s'applique a l'étude de la distribution des points rationnels d'une telle variété definie sur un corps fini ou sur le corps des nombres rationnels.
Let K be an algebraic number field of degree n and discriminant d. Let K(1),…, K(n) be the embeddings of the field. Then n = r1 + 2r2 where K(1), …, K(rl) are real and the remainder complex, satisfying . The conjugates of the number μ in K(i) are denoted by μ(i.
In the terminology of Birget and Rhodes [3], an expansion is a functor F from the category of semigroups into some special category of semigroups such that there is a natural transformation η from F to the identity functor for which ηs is surjective for every semigroup S. The three expansions introduced in [3] have proved to be of particular interest when applied to groups. In fact, as shown in [4], Ĝ(2) are isomorphic for any group G, is an E-unitary inverse monoid and the kernel of the homomorphism ηG is the minimum group congruence on . Furthermore, if G is the free group on A, then the “cut-down to generators” which is a subsemigroup of is the free inverse semigroup on A. Essentially the same result was given by Margolis and Pin [12].
There exists a family of pairwise disjoint congruent infinite circular cylinders such that no two cylinders of are parallel and the density of is greater than zero.
Traditionally the theory of modular forms has been and still is, one of the most powerful tools in number theory. Recently it has also been successfully applied to resolve some long outstanding problems in seemingly unrelated fields. Our aim in this book is to describe three such applications, developing along the way the necessary methods and material from the theory of modular forms. Briefly, the problems we examine are the following:
(A) Ruziewicz's problem.
The problem is whether the Lebesgue measure λ on the n-sphere Sn is the unique rotationally invariant mean on L∞(Sn). To put it in another context, an amenable topological group G is one which carries an invariant mean on L∞(G). Uniqueness of such a mean is a difficult question and seldom discussed. Actually, Ruziewicz in the 1920's posed the problem of the uniqueness of rotationally invariant finitely additive measures defined on Lebesgue sets on Sn. The relation between these problems is that an invariant mean on L∞(Sn) is a finitely additive measure v which is moreover absolutely continuous with respect to Lebesgue measure λ, i.e., v(E) = 0 whenever λ(E) = 0. Tarski [Tar] has remarked that it follows from the Hausdorff–Banach–Tarski paradoxical decompositions of Sn, n ≥ 2, that any rotationally invariant finitely additive measure on Sn, n ≥ 2, must be absolutely continuous with respect to λ. Hence for n ≥ 2 the invariant mean and Ruziewicz problems are equivalent.
These notes are an expanded version of the Wittemore Lectures given at Yale in November 1988. The material presented in the four chapters is more or less selfcontained. On the other hand, in the section at the end of each chapter called ‘Notes and comments,’ it is assumed that the reader is familiar with more advanced and sophisticated notions from the theory of automorphic forms. Some of the material presented here overlaps with a forthcoming book, ‘Discrete groups, expanding graphs and invariant measures’ by A. Lubotzky. The points of view, emphasis, and presentation in that book and the present notes are sufficiently different that we decided to keep the two works separate. The reader is encouraged to look at both treatments of the material.