gl(λ) and differential operators preserving polynomials

We discuss a certain generalization of gl _n (), and show how it is connected to polynomial differential operators that leave the polynomial space invariant.     

Connectedness properties of the range of vector and semimeasures

It is shown that the range of a non-atomic semimeasure as well as the range of a non-atomic measure defined on a -ring with values in a Banach space or even in an abelian topological Hausdorff group is arcwise connected.     

K-Theory for the Integer Heisenberg Groups

We give a closed formula for topological K-theory of the homogeneous space N/, where is the standard integer lattice in the simply connected Heisenberg Lie group N of dimension 2n+1, n . The main tools in our calculations are obtained by computing diagonal forms for certain incidence matrices that arise naturally in combinatorics.     

The free loop space and the algebraic k-theory of spaces

Let A(X) be the space defined by Waldhausen whose homotopy groups define the algebraic K-groups of the space X and let . Here (X) denotes the free loop space of X and Q denotes the functor . For X = Y, the suspension of a connected space Y, we shall prove that the homotopy fibers Ã(X), B(X) of the maps A(X) A (point), B(X) B (point) are equivalent as infinite loop spaces.     

Neither first countable nor Cech-complete spaces are maximal Tychonoff connected

A connected Tychonoff space is called maximal Tychonoff connected if there is no strictly finer Tychonoff connected topology on . We show that if is a connected Tychonoff space and locally separable spaces, locally \v{C}ech-complete spaces, first countable spaces, then is not maximal Tychonoff connected. This result is new even in the cases where is compact or metrizable.

     

Homotopy of spaces of diffeomorphisms of some three-dimensional manifolds

The goal of the paper is to calculate the homotopy type of the space of diffeomorphisms for most orientable three-dimensional manifolds with finite fundamental group containing the Klein bottle. The fundamental group of such a manifold Q has the form <a, b ¦abab ^–1=1,a ^mb²ⁿ=1>. As m and n one can have any relatively prime natural numbers; these numbers m, n determine the manifold Q up to diffeomorphism. Let K be a Klein bottle lying in Q and let P be a closed tubular neighborhood in Q of this Klein bottle K. We denote by Diff_o(Q) the connected component of the space of diffeomorphisms QQ containing id Q, and by E₀(K, Q) the connected component of the space of imbeddings KQ containing the inclusion KQ; analogously we define E₀(K, P). The main results of the paper are the following two theorems. THEOREM 1. If m, n1, then the space Diff_o(Q) is homotopy equivalent with a circle. THEOREM 2. If m, n1, then the inclusion E₀(K, P) E₀(K, Q) is a homotopy equivalence. With the help of familiar results on spaces of diffeomorphisms of irreducible manifolds which are sufficiently large, Theorem 1 reduces without difficulty to Theorem 2. The main difficulty is the proof of Theorem 2. This proof develops a technique of Hatcher and the author which deals with spaces of PL-homeomorphisms and diffeomorphisms of irreducible manifolds which are sufficiently large. In the paper we use a different structure definition of the class of manifolds considered. It is easy to verify that these definitions are equivalent.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 122, pp. 72–103, 1982.     

A construction of representations of affine Weyl groups

Let G be a complex, semisimple, simply connected algebraic group withLie algebra . We extend scalars to the power series field in one variable C(()), and consider the space of Iwahori subalgebras containing a fixed nil-elliptic element of C(()),i.e. fixed point varieties on the full affine flag manifold. We definerepresentations of the affine Weyl group in the homology of these varieties,generalizing Kazhdan and Lusztig's topological construction of Springer'srepresentations to the affine context.     

A monotone path-connected set with outer radially lower continuous metric projection is a strict sun

A monotone path-connected set is known to be a sun in a finite-dimensional Banach space. We show that a B-sun (a set whose intersection with each closed ball is a sun or empty) is a sun. We prove that in this event a B-sun with ORL-continuous (outer radially lower continuous) metric projection is a strict sun. This partially converses one well-known result of Brosowski and Deutsch. We also show that a B-solar LG-set (a global minimizer) is a B-connected strict sun.     

Ratios of Norms for Polynomials and Connected n-width Problems

Let be a bounded simply connected domain with boundary Γ and let be a regular compact set with connected complement. In this paper we investigate asymptotics of the extremal constants:

Global Optimization: On Pathlengths in Min-Max Graphs

Let f be a smooth nondegenerate real valued function on a finite dimensional, compact and connected Riemannian manifold. The bipartite min-max graph is defined as follows. Its nodes are formed by the set of local minima and the set of local maxima. Two nodes (a local minimum and a local maximum) are connected in by means of an edge if some trajectory of the corresponding gradient flow connects them. Given a natural number k, we construct a function f such that the length of the shortest path in between two specific local minima exceeds k. The latter construction is independent of the underlying Riemannian metric.     

When do connected spaces have nice connected preimages?

We prove that every connected Tychonoff space is an open monotone continuous image of a connected strictly -discrete left-separated Tychonoff space. For wide classes of connected spaces it is established that they have a finer Hausdorff strictly -discrete connected topology. Another result is that a finer Tychonoff connected strictly -discrete topology exists for any Tychonoff topology with a countable network. We show that there are Tychonoff connected spaces with countable network which are not continuous images of connected second countable spaces. It is established also that every connected Tychonoff space is an open retract of a connected homogeneous Tychonoff space, while it is not always possible to find a finer connected homogeneous topology on .

     

Quasigeodesics outside horoballs

Let be the path metric space obtained from a Hadamard manifold X by removing a collection of pairwise disjoint open horoballs from X. In case X is a rank one symmetric space, certain properties of quasigeodesics in have been used to derive results about lattices in X. For two such properties we give new proofs that simultaneously apply to the case where X is a Hadamard space with sectional curvature -a ²K-1,1a<2. In this case, as an application of one of these properties, we show that every lattice in X is biautomatic.     

A Foliation of the Space of Conjugacy Classes of Representations of a Surface Group

Let be the fundamental group of a closed orientable surface of genus g 1, and let R(, G)/G be the space of conjugacy classes of representations of into a connected real reductive Lie group G. Motivated by the theory of geometric quantization, we define a map ¯ on R(, G)/G and investigate whether the fibres of ¯ are isotropic with respect to the natural symplectic structure on R(, G)/G. If g = 2 and G = SU(2), then the foliation given by the fibres of ¯ is equivalent to a real polarization defined by Weitsman, and we reprove his result that the fibres are isotropic in this case. If g = 1 then the fibres of ¯ are also isotropic, but we give an example to show that in general they are not.     

On Hardy’s uncertainty principle for connected nilpotent Lie groups

In (Kaniuth and Kumar in Math. Proc. Camb. Phil. Soc. 131, 487–494, 2001) Hardy’s uncertainty principle for was generalized to connected and simply connected nilpotent Lie groups. In this paper, we extend it further to connected nilpotent Lie groups with non-compact centre. Concerning the converse, we show that Hardy’s theorem fails for a connected nilpotent Lie group G which admits a square integrable irreducible representation and that this condition is necessary if the simply connected covering group of G satisfies the flat orbit condition.     

Solutions of affine stochastic functional differential equations in the state space

We consider solutions of affine stochastic functional differential equations on . The drift of these equations is specified by a functional defined on a general function space which is only described axiomatically. The solutions are reformulated as stochastic processes in the space . By representing such a process in the bidual space of we establish that the transition functions of this process form a generalized Gaussian Mehler semigroup on . This way the process is characterized completely on since it is Markovian. Moreover we derive a sufficient and necessary condition on the underlying space such that the transition functions are even an Ornstein-Uhlenbeck semigroup. We exploit this result to associate a Cauchy problem in the function space to the stochastic functional differential equation.      

Mixed Hodge structure in cyclic homology and algebraic K-theory, 1

Deligne defined the notion of a mixed Hodge structure (MHS) and proved that every quasiprojective variety over has a natural MHS on its cohomology. This paper establishes similar results for cyclic homology and the algebraic K-theory of simply connected quasi-projective varieties over . In the nonsimply connected case, an MHS is established on certain quotient groups of algebraic K-theory.Supported by a NSERC University Research Fellowship and operating grant.     

On 2-Homogeneity of Monounary Algebras

Fraïssé introduced the notion of a k-set-homogeneous relational structure. In the present paper the following classes of monounary algebras are described: --the class of all algebras which are 2-set-homogeneous with respect to subalgebras, connected subalgebras, connected partial subalgebras, respectively, and --the class of all algebras which are 2-homogeneous with respect to subalgebras, connected subalgebras, connected partial subalgebras, respectively.     

A remark on a paper of B. R. Gelbaum

Summary In this paper the following generalization of a theorem by B.R. Gelbaum is proved:Let (K, d) be a compact, connected metric space. Let B denote the Borel sets of (K, d), and P be a probability measure on B with P(G)O for any nonempty open G, f, gC(K,d) independent random variables on (K,B,P) and let g satisfy the following assumption:There is an y _o such that g ^–1(y₀) is a finite nonempty set. Then f is a constant function.Examples show that the assumptions of this theorem are essential.     

Neumann problem for second-order elliptic equations in domains with edges on the boundary

It is proved that the generalized solution of the Neumann problem for a second-order elliptic equation in a domain Rⁿ, whose boundary has smooth nonintersecting (n-2)-dimensional edges, belongs to some weighted Sobolev space. One establishes coercive estimates of the solution in the norm of this space.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 127, pp. 7–48, 1983.     

Some generalizations of the classical moment problem

The article is devoted to two generalizations of the classical power moment problem, namely: 1) instead of representing the moment sequence by ⁿ , a representation by polynomialsP _n (), ¹, connected with a Jacobi matrix, appears; 2) in the representation, instead of ⁿ , the expression ⁿ figures, where is a real generalized function (i.e., we investigate some infinite-dimensional moment problem).The work is partially supported by the DFG, Project 436 UKR 113/39/0 and by the CRDF, Project UM1-2090.