Analytische Vektoren von Faltungshalbgruppen II. Funktionenräume,auf lokalkompakten Gruppen

In this paper the investigations of [3], [4], [5] are continued. LetG be a locally compact group. First we show that in general there is no rich subspace of functions of the Bruhat-spaceD (G), whose, elements are analytical vectors for any convolution semigroup of probability measures. On the other hand we are able to construct dense subspaces ofC ₀ (G) of analytical vectors, ifG is a Moore-group or a symmetric Riemannian space. We study properties of these subspaces and their relations to the structure, of the groupG.

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Herrn Prof. Dr. L. Schmetterer zum 60. Geburtstag gewidmet     

Invariants de Von Neumann des faisceaux analytiques cohérents

In order to study the group of holomorphic sections of the pull-back to the universal covering space of an holomorphic vector bundle on a compact complex manifold, it would be convenient to have a cohomological formalism, generalizing Atiyah's index theorem. In [Eys99], such a formalism is proposed in a restricted context. To each coherent analytic sheaf on a n-dimensionnal smooth projective variety and each Galois infinite unramified covering , whose Galois group is denoted by , cohomology groups denoted by are attached, such that: 1. The underly a cohomological functor on the abelian category of coherent analytic sheaves on X. 2. If is locally free, is the group of holomorphic sections of the pull-back to of the holomorphic vector bundle underlying . 3. belongs to a category of -modules on which a dimension function with real values is defined. 4. Atiyah's index theorem holds [Ati76]: The present work constructs such a formalism in the natural context of complex analytic spaces. Here is a sketch of the main ideas of this construction, which is a Cartan-Serre version of [Ati76]. A major ingredient will be the construction [Farb96] of an abelian category containing every closed -submodule of the left regular representation. In topology, this device enables one to use standard sheaf theoretic methods to study Betti numbers [Ati76] and Novikov-Shubin invariants [NovShu87]. It will play a similar r?le here. We first construct a -cohomology theory () for coherent analytic sheaves on a complex space endowed with a proper action of a group such that conditions 1-2 are fulfilled. The -cohomology on the Galois covering of a coherent analytic sheaf onX is the ordinary cohomology of a sheaf on X obtained by an adequate completion of the tensor product of by the locally constant sheaf on X associated to the left regular representation of the discrete group in the space of functions on . Then, we introduce an homological algebra device, montelian modules, which can be used to calculate the derived category of and are a good model of the Čech complex calculating -cohomology. Using this we prove that , if X is compact. This is stronger than condition 3, since this also yields Novikov-Shubin type invariants. To explain the title of the article, Betti numbers and Novikov-Shubin invariants of are the Von Neumann invariants of the coherent analytic sheaf . We also make the connection with Atiyah's -index theorem [Ati76] thanks to a Leray-Serre spectral sequence. From this, condition 4 is easily deduced.

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Received: 30 October 1998 / Published online: 8 May 2000     

Zwei Klassen lokalkompakter maximal fastperiodischer Gruppen

In this paper we study the class of all locally compact groupsG with the property that for each closed subgroupH ofG there exists a pair of homomorphisms into a compact group withH as coincidence set, and the class of all locally compact groupG with the property that finite dimensional unitary representations of subgroups ofG can be extended to finite dimensional representations ofG. It is shown that [MOORE]-groups (every irreducible unitary representation is finite dimensional) have these two properties. A solvable group in is a [MOORE]-group. Moreover, we prove a structure theorem for Lie groups in the class [MOORE], and show that compactly generated Lie groups in [MOORE] have faithful finite dimensional unitary representations.     

The existence of inner invariant means on L(G)

The purpose of this paper is to generalize the concepts of amenability for locally compact groups and inner amenability for discrete groups by considering the existence of inner invariant means. Based on this generalization, locally compact groups can be classified as so called [IA] groups or non-[IA] groups. A number of equivalent conditions characterizing [IA] groups are given. Also the possibility of inner invariant extension of the Dirac measure δ_e is discussed.     

Zur Klassifikation differenzierbarer Gruppen

We want to classify differentiable groups in terms of Lie groups and formal groups. This note contains a first essential step in this direction: Differentiable groups can always be embedded as dense subgroups of locally compact groups.

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Herrn W. Thimm zum 60. Geburtstag gewidmet     

Gluing Compact Matrix Quantum Groups

We study glued tensor and free products of compact matrix quantum groups with cyclic groups – so-called tensor and free complexifications. We characterize them by studying their representation categories and algebraic relations. In addition, we generalize the concepts of global colourization and alternating colourings from easy quantum groups to arbitrary compact matrix quantum groups. Those concepts are closely related to tensor and free complexification procedures. Finally, we also study a more general procedure of gluing and ungluing.

     

Topological regular variation: I. Slow variation

Motivated by the Category Embedding Theorem, as applied to convergent automorphisms (Bingham and Ostaszewski (in press) [11]), we unify and extend the multivariate regular variation literature by a reformulation in the language of topological dynamics. Here the natural setting are metric groups, seen as normed groups (mimicking normed vector spaces). We briefly study their properties as a preliminary to establishing that the Uniform Convergence Theorem (UCT) for Baire, group-valued slowly-varying functions has two natural metric generalizations linked by the natural duality between a homogenous space and its group of homeomorphisms. Each is derivable from the other by duality. One of these explicitly extends the (topological) group version of UCT due to Bajšanski and Karamata (1969) [4] from groups to flows on a group. A multiplicative representation of the flow derived in Ostaszewski (2010) [45] demonstrates equivalence of the flow with the earlier group formulation. In companion papers we extend the theory to regularly varying functions: we establish the calculus of regular variation in Bingham and Ostaszewski (2010) [13] and we extend to locally compact, σ-compact groups the fundamental theorems on characterization and representation (Bingham and Ostaszewski (2010) [14]). In Bingham and Ostaszewski (2009) [15], working with topological flows on homogeneous spaces, we identify an index of regular variation, which in a normed-vector space context may be specified using the Riesz representation theorem, and in a locally compact group setting may be connected with Haar measure.     

Essential subgroups of topological groups

We study the class Wof Hausdorff topological groups Gfor which the following two cardinal invariants coincide

ES(G)=min{|H|:H≤ Gdense and essential}

TD(G)=min{|H|:H≤ Gtotally dense}

We prove that W contains the following classes:locally compact abelian groups, compact connected groups, countably compact totally discon¬nected abelian groups, topologically simple groups, locally compact Abelian groups when endowed with their Bohr topology, totally minimal abelian groups and free Abelian topological groups. For all these classes we are also able to giv ean explicit computation of the common value of ESand TD.     

Fuzzy (Θ, S)-continuity and fuzzy (Θ, S)-closed graphs

The concept of (,s)-continuity [6] is considered and studied in fuzzy setting. It is seen that althought it is independent with each of the concepts of fuzzy continuity [2], fuzzy -continuity [10], fuzzy almost continuity [1] and fuzzy semicontinuity [1]; it implies fuzzy weak continuity [1], but the converse may not be true. The image of a compact fts [2] under a fuzzy (,s)-continuous surjective function isS-closed [5]. Finally the concepts of fuzzy (,s)-closed graphs, fuzzy (,s)-T ₂ spaces and fuzzy Urysohn spaces are introduced and mainly their connections with fuzzy (,s)-continuity are studied.     

An Isometric Representation of the Dual of {\user1{\mathcal{C}}}{\left( {X,\mathbb{R}} \right)}

Many structures in functional analysis are introduced as the limit of an inverse (aka projective) system of seminormed spaces [2, 3, 8]. In these situations, the dual is moreover equipped with a seminorm. Although the topology of the inverse limit is seldom metrizable, there is always a natural overlying locally convex approach structure. We provide a method for computing the adjoint of this space, by showing that the dual of a limit of locally convex approach spaces becomes a co-limit in the category of seminormed spaces. As an application we obtain an isometric representation of the dual space of real valued continuous functions on a locally compact Hausdorff space X, equipped with the compact open structure.     

Irreducible decompositions of unitary representations of infinite- dimensional groups

This paper concerns the problem of irreducible decompositions of unitary representations of topological groups G, including the group Diff₀(M) of diffeomorphisms with compact support on smooth manifolds M. It is well known that the problem is affirmative, when G is a locally compact, separable group (cf. [3, 4]). We extend this result to infinite-dimensional groups with appropriate quasi-invariant measures, and, in particular, we show that every continuous unitary representation of Diff₀(M) has an irreducible decomposition under a fairly mild condition. This research was partially supported by a Grant-in-Aid for Scientific Research (No.14540167), Japan Socieity of the Promotion of Science.     

Nouvelles extensions des équations intégro-différentielles non linéaires de Volterra

Summary In the framework of the authors' research papers devoted to studies concerningmathematical systems with mixed structures and in particular to studies on nonlinear integro-differential equations of Volterra and Picone types [5], [14]–[15], an initial value problem concerning a new extension of Volterra's integro-differential equations is considered and the existence, the unicity and the stability of its solution is proved.

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A M. le Professeur Wolfgang Gröbner pour son 75-e anniversaire

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The research reported in this paper was supported in part by the National Research Council of Canada through the University of Alberta by Grant NRC-A4345.     

Quantum groups at roots of ±1

Apart from being of interest in its own right, the representation theory for quantum groups at roots of unity enters into Lusztig’s programme (see e.g. [Lus94]) for determining the irreducible characters of semi-simple algebraic groups in characteristic p > 0. In [AJS94] this connection plays a key role. There our assumption is that the root of unity has odd order (bigger than the Coxeter number).

Using the recent work of Kashiwara - Tanisaki, [KT95a] and [KT95b] together with the Kazhdan-Lusztig equivalence of categories, [KL93], [KL94] and [Lus94] it is possible to get rid of this oddness assumption as far as the determination of irreducible characters for quantum groups goes, see also [Kan95]. In this note we show how we can do this much more directly staying inside the theory for quantum groups. To be more specific we prove the following result (see below for more details and notations).     

Orthogonalkompakte Teilmengen topologischer Vektorverbände

The criterion of Dunford-Pettis for weak compactness in Banach lattices of L¹() type can be derived from a characterisation of weak sequentially complete topological vector lattices. This can be done by introducing a concept which reduces to uniform integrability in the L¹() case ([1], [8]). In other cases suitable choice of the topology leads to definitions given by [4], [9], [11] and [12]. It is shown in this paper that the orthogonally compact subsets of a Banach lattice are characterized as those relatively weakly compact sets on which the norm and the order topology agree.

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Der Inhalt dieser Arbeit ist ein Auszug aus der Dissertation des Autors an der Universität Dortmund     

Ein stabiles Schichtenverfahren für allgemeine lineare Evolutionsgleichungen

Summary By generalizing Rothe's method of lines to initial value problemsu=A u, u(0)=u ₀ in Banach-spaces one obtains an approximation method that can be investigated within the theory of Lax and richtmyer [2]. It is well known that the generalized solutions of properly posed problems are semi-groups of class (C₀). In this paper the relation between the infinitesimal generator of that semi-group and the operatorA of the initial-value problem is discussed. As a consequence of the representation theorem of Hille-Yosida-Phillips one obtains that the method in question is stable iff the initial value problem is properly posed.

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Die Arbeit ist die gekürzte Fassung eines Teils meiner Dissertation [7], die ich am Lehrstuhl von Prof. G. Hämmerlin anfertigte. Ihm danke ich herzlich für die Unterstützung bei der Anfertigung der Arbeit.     

Intégration Symplectique des Variétés de Poisson Régulières

Asymplectic integration of a Poisson manifold (M, Λ) is a symplectic groupoid (Γ,η) whichrealizes the given Poisson manifold, i.e. such that the space of units Γ₀ with the induced Poisson structure Λ₀ is isomorphic to (M, Λ). This notion was introduced by A. Weinstein in [28] in order to quantize Poisson manifolds by quantizing their symplectic integration. Any Poisson manifold can be integrated by alocal symplectic groupoid ([4], [13]) but already for regular Poisson manifolds there are obstructions to global integrability ([2], [6], [11], [17], [28]). The aim of this paper is to summarize all the known obstructions and present a sufficient topological condition for integrability of regular Poisson manifolds; we will indeed describe a concrete procedure for this integration. Further our criterion will provide necessary and sufficient if we require Γ to be Hausdorff, which is a suitable condition to proceed to Weinstein’s program of quantization. These integrability results may be interpreted as a generalization of the Cartan-Smith proof of Lie’s third theorem in the infinite dimensional case.

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Recherche supportée par D.G.I.C.Y.T. Espagne (Proyecto PB90-0765) et Xunta de Galicia (Proxecto XUGA20704B90)     

Sull'esistenza delle soluzioni delle equazioni differenziali ordinarie in forma implicita negli spazi di Banach

Summary This paper deals with the existence of solutions for the implicit Cauchy problem F(t, x, x)=_B, x(t₀)=x₀ in a Banach space B. By using the Kuratowski and the Hausdorff measure of non compactness, we prove an existence theorem for the previous problem (Teorema 1.1) and its extension to non compact intervals (Teorema 2.1). These results generalize the previous ones by R.Conti [1] (in the case B=R), G.Pulvirenti [2] and T. Dominguez Benavides [3], [4] (in the general case). In particular, we relax a Lipschitz condition assumed by all of the abovementioned authors. Some applications of Teorema 2.1 are presented.

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Lavoro eseguito nell'ambito del G.N.A.F.A. del C.N.R.     

Weakly Compact Composition Operators on Locally Convex Spaces

Let E be a complete, barrelled locally convex space, let V = (v_n) be an increasing sequence of strictly positive, radial, continuous, bounded weights on the unit disc 𝔻 of the complex plane, and let φ be an analytic self map on 𝔻. The composition operators C_φ : f → f ○ φ on the weighted space of holomorphic functions HV (𝔻, E) which map bounded sets into relatively weakly compact subsets are characterized. Our approach requires a study of wedge operators between spaces of continuous linear maps between locally convex spaces which extends results of Saksman and Tylli [31, 32], and a representation of the space HV (𝔻, E) as a space of operators which complements work by Bierstedt , Bonet and Galbis [4] and by Bierstedt and Holtmanns [6].     

Hypertopologies on function spaces

The aim of this paper is to continue Naimpally’s seminal papers [16], [17], [18], i.e. we investigate topological properties of spaces which force the coincidence of convergences of functions associated with different hyperspace topologies. For example a metric spaceX is locally compact iff the topological convergence and the convergence induced by the Fell topology coincide onC(X,IR). Moreover, the proximal topology on the space of functions, not necessarily continuous, is studied in great detail.     

Dualità per alcune classi di moduliE-compatti

Summary Starting from a topological module E over a commutative discrete ring A, the category C(E) of E-compact modules is defined as the class of all A-modules topologically isomorphic to closed submodules of direct product of copies of E. Under suitable assumptions it is shown that C(E) is dual of the category of abstract A-modules M for whichHom _A(M, E) separates points of M. The duality theory so obtained contains as particular cases Pontryagin's duality between discrete and compact abelian groups and Macdonald's duality between lineary discrete and linearly compact modules over a complete local ring. There are also some applications to the theory of linearly compact modules over noetherian rings.

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Entrata in Redazione il 10 aprile 1976.

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Lavoro eseguito nell'ambito dell'attività dei gruppi di ricerca matematici del C.N.R.