Proof of a conjecture on multisets of hook numbers

A conjecture of Regev and Vishik on the equality of two multisets of hook numbers is proved. Supported in part by N.S.F. Grant No. DMS-94-01197. Supported in part by N.S.F. Grant No. DMS-95-00646.     

Practicing algebra in late antiquity: The problem-solving of Diophantus of Alexandria

Medieval algebra is distinguished from other arithmetical problem-solving techniques by its structure and technical vocabulary. In an algebraic solution one or several unknowns are named, and via operations on the unknowns the problem is transferred to the artificial setting of an equation expressed in terms of the named powers, which is then simplified and solved. In this article we examine Diophantus? Arithmetica from this perspective. We find that indeed Diophantus? method matches medieval algebra in both vocabulary and structure. Just as we see in medieval Arabic and Italian algebra, Diophantus worked out the operations expressed in the enunciation of a problem prior to setting up a polynomial equation. Further, his polynomials were regarded as aggregations with no operations present.     

The determination of convex bodies from derivatives of section functions

It is known that non-symmetric convex bodies generally cannot be characterized by the volumes of hyperplane sections through one interior point. Falconer and Gardner, however, independently proved that volumes of hyperplane sections through two different interior points determine the body uniquely. We prove that if −1 < q < n − 1 is not an integer, then the derivatives of the order q at zero of parallel section functions at one interior point completely characterize convex bodies in . If 0 ≤ q < n − 1 is an integer then one needs the derivatives of order q at two different interior points (except for the case where q = n − 2, q odd), generalizing the results of Falconer and Gardner. The first named author was partially supported by the NSF grant DMS 0455696. Received: 31 January 2006     

The way of Diophantus: Some clarifications on Diophantus' method of solution

In the introduction of the Arithmetica Diophantus says that in order to solve arithmetical problems one has to “follow the way he (Diophantus) will show.” The present paper has a threefold objective. Firstly, the meaning of this sentence is discussed, the conclusion being that Diophantus had elaborated a program for handling various arithmetical problems. Secondly, it is claimed that what is analyzed in the introduction is definitions of several terms, the exhibition of their symbolism, the way one may operate with them, but, most significantly, the main stages of the program itself. And thirdly, it is argued that Diophantus' intention in the Arithmetica is to show the way the stages of his program should be practically applied in various arithmetical problems.     

Why Rob Archimedes of his Lemma?

The method of exhaustion is one of the greatest achievements of Greek mathematics, but the history of its development is not clear. First and foremost Archimedes’ role has been keenly debated, by and large undermined, so that even his name seems condemned to disappear in the name of the Eudoxus-Archimedes Lemma. In this paper we try to revaluate his role by a new interpretation (or, more precisely, by the refinement of an old one) of the historical development of the theory, underlining the theoretical relevance of the problem of addition/subtraction and comparison between curves. Dedicated to the memory of Professor Aldo Cossu     

On proper coverings of Artin stacks

We prove that every separated Artin stack of finite type over a noetherian base scheme admits a proper covering by a quasi-projective scheme. An application of this result is a version of the Grothendieck existence theorem for Artin stacks.     

A solution of Hadwiger's covering problem for zonoids

For a convex body M ⁿ byb(M) the least integerp is denoted, such that there are bodiesM ₁, ...,M _p each of which is homothetic toM with a positive ratiok<1 andM ₁...M _p M. H. Martini has proved [7] thatb(M)<-3·2 ^n–2 for every zonotope M ⁿ , which is not a parallelotope.In the paper this Martini's result is extended to zonoids. In the proof some notions and facts of real functions theory are used (points of density, approximative continuity).     

Uniquely factorizable elements and solvability of finite groups

In a finite group G every element can be factorized in such a way that there is one factor for each prime divisor p of | G |, and the order of this factor is p^α for some integer α ≧ 0. We define g ∈G to be uniquely factorizable if it has just one such factorization (whose factors must be pairwise commuting). We consider the existence of uniquely factorizable elements and its relation to the solvability of the group. We prove that G is solvable if and only if the set of all uniquely factorizable elements of G is the Fitting subgroup of G. We also prove various sufficient conditions for the non-existence of uniquely factorizable elements in non-solvable groups. Received: 9 June 2005     

Sections and projections of homothetic convex bodies

For a pair of convex bodies K₁ and K₂ in Euclidean space , n ≥ 3, possibly unbounded, we show that K₁ is a translate of K₂ if either of the following conditions holds: (i) the orthogonal projections of K₁ on 2-dimensional planes are translates of the respective orthogonal projections of K₂, (ii) there are points p₁ ∈K₁ and p₂ ∈K₂ such that for every pair of parallel 2-dimensional planesL₁and L₂ through p₁ and p₂, respectively, the section K₁ ∩ L₁is a translate of K₂ ∩ L₂.     

A quick proof of Höbinger-Burton-Larman's theorem

Through the notion of projective center of symmetry of a convex body we will give a quick proof and clarify the ideas surrounding Höbinger's problem, originally proved by Burton and Larman in [1].     

Steiner symmetrization using a finite set of directions

Let v₁,…,vm$v_1,\dots ,v_m$ be a finite set of unit vectors in Rn${\mathbb{R}}^n$. Suppose that an infinite sequence of Steiner symmetrizations are applied to a compact convex set K   in Rn${\mathbb{R}}^n$, where each of the symmetrizations is taken with respect to a direction from among the vi$v_i$. Then the resulting sequence of Steiner symmetrals always converges, and the limiting body is symmetric under reflection in any of the directions vi$v_i$ that appear infinitely often in the sequence. In particular, an infinite periodic sequence of Steiner symmetrizations always converges, and the set functional determined by this infinite process is always idempotent.     

ON STABLE LINE SEGMENTS IN ALL TRIANGULATIONS OF A PLANAR POINT SET

Abstract. Let S be a set of finite plauar points. A llne segment L(p, q) with p, q E Sis called a stable line segment of S, if there is no Line segment with two endpoints in S intersecting L(p, q). In this paper, some geometric properties of the set of all stable line segments     

Asymptotics for the zeros of the generalized Bessel polynomials

Summary We investigate the location of the zeros of the normalized generalized Bessel polynomials and the normalized reversed generalized Bessel polynomials. Also, the rate at which these zeros approach certain well-defined curves is investigated. On the basis of numerical computations and graphs, four new conjectures are proposed.Dedicated to Richard S. Varga on the occasion of his sixtieth birthday (October 9, 1988)This research was made possible and supported by a Butler University Fellowship Award     

Generalized notions of amenability

New notions of amenability and contractability are introduced. Examples are given to show that for most of the new notions, the corresponding class of Banach algebras is larger than that for the classical amenable algebras introduced by Johnson. General theory is developed for these notions, and studied for several concrete classes of Banach algebras; special consideration is given to Banach algebras defined on locally compact groups.     

Some remarks on the meaning of equality in Diophantos’s Arithmetica

Diophantos in Arithmetica, without having defined previously any concept of “equality” or “equation,” employs a concept of the unknown number as a tool for solving problems and finds its value from an equality ad hoc created. In this paper we analyze Diophantos’s practices in the creation and simplification of such equalities, aiming to adduce more evidence on certain issues arising in recent historical research on the meaning of the “equation” in Diophantos’s work.     

On convex bodies of constant width

We present an alternative proof of the following fact: the hyperspace of compact closed subsets of constant width in Rn is a contractible Hilbert cube manifold. The proof also works for certain subspaces of compact convex sets of constant width as well as for the pairs of compact convex sets of constant relative width. Besides, it is proved that the projection map of compact closed subsets of constant width is not 0-soft in the sense of Shchepin, in particular, is not open.     

Reducing subspaces of compressed analytic Toeplitz operators on the Hardy space

In this paper we discuss necessary conditions and sufficient conditions for the compression of an analytic Toeplitz operator onto a shift coinvariant subspace to have nontrivial reducing subspaces. We give necessary and sufficient conditions for the kernel of a Toeplitz operator whose symbol is the quotient of two inner functions to be nontrivial and obtain examples of reducing subspaces from these kernels. Motivated by this result we give necessary conditions and sufficient conditions for the kernel of a Toeplitz operator whose symbol is the quotient of two inner functions to be nontrivial in terms of the supports of the two inner functions. By studying the commutant of a compression, we are able to give a necessary condition for the existence of reducing subspaces on certain shift coinvariant subspaces.     

Vanishing evaluations of simple functors

The classification of simple biset functors is known, but the evaluation of a simple biset functor at a finite group G$G$ may be zero. We investigate various situations where this happens, as well as cases where this does not occur. We also prove a closed formula for such an evaluation under some restrictive conditions on  G$G$.     

Finite-dimensional algebraic representations of the infinite phylon group

The concept of phylon is introduced as a generalisation of derivative strings, differential strings and new tensors. The behaviour of phyla under change of coordinates is given by finite-dimensional algebraic representations of a very large group, the infinite phylon group. These representations are studied from both the general and the matrix points of view. Various examples of phyla are given, mainly from a statistical context. The basic structure of these representations is given.     

Epimorphisms of separated totally convex spaces

We give characterizations of the epimorphisms in the categories of open and separated totally convex and (pre)separated absolutely convex spaces.