The τc -topology on locally compact foundation semigroups

2009 ◽  
Vol 46 (1) ◽  
pp. 25-35
Author(s):  
Ali Ghaffari
Keyword(s):  
Topological Semigroup ◽  
Weak Topology ◽  
The Other ◽  
Bounded Subset ◽  
Almost Periodic ◽  
Norm Topology ◽  
Locally Compact

Given a foundation locally compact Hausdorff topological semigroup S , we consider on Ma ( S )* the τc -topology, i.e. the weak topology under all right multipliers induced by measures in Ma ( S ). For such an arbitrary S the τc -topology is not weaker than the weak*-topology and not stronger than the norm topology on Ma ( S )*. However, a further investigation shows that for compact S the norm topology and τc -topology coincide on every norm bounded subset of Ma ( S ). Among the other results we mention that except for discrete S the τc -topology is always different from the norm-topology. Finally, we give some results about τc -almost periodic functionals.

scholarly journals The convolution-induced topology onL∞(G)and linearly dependent translates inL1(G)

1982 ◽  
Vol 5 (1) ◽  
pp. 11-20 ◽  
Author(s):  
G. Crombez ◽  
W. Govaerts
Keyword(s):  
Weak Topology ◽  
Trigonometric Polynomials ◽  
Major Result ◽  
Almost Periodic ◽  
Convolution Operators ◽  
Norm Topology ◽  
Locally Compact ◽  
Finite Dimensional ◽  
Hausdorff Group ◽  
Induced Topology

Given a locally compact Hausdorff groupG, we consider onL∞(G)theτc-topology, i.e. the weak topology under all convolution operators induced by functions inL1(G). As a major result we characterize the trigonometric polynomials on a compact group as those functions inL1(G)whose left translates are contained in a finite-dimensional set. From this, we deduce thatτcis different from thew∗-topology onL∞(G)wheneverGis infinite. As another result, we show thatτccoincides with the norm-topology if and only ifGis discrete. The properties ofτcare then studied further and we pay attention to theτc-almost periodic elements ofL∞(G).

On the supports of Gauss measures on algebraic groups

1984 ◽  
Vol 96 (3) ◽  
pp. 437-445 ◽  
Author(s):  
M. McCrudden
Keyword(s):  
Topological Group ◽  
Topological Semigroup ◽  
Weak Topology ◽  
Algebraic Groups ◽  
Locally Compact ◽  
Compact Topological Group ◽  
Borel Measures ◽  
Image Position ◽  
Locally Compact Topological Group

For any locally compact topological group G let M(G) denote the topological semigroup of all probability (Borel) measures on G, furnished with the weak topology and with convolution as the multiplication. A Gauss semigroup on G is a homomorphism t→ μt of the strictly positive reals (under addition) into M(G) such that(i) no μt is a point mesaure,(ii) for each neighbourhood V of 1 in G we have

scholarly journals Uniqueness theorem for Fourier transformable measures on LCA groups

2020 ◽  
Vol 54 (2) ◽  
pp. 211-219
Author(s):  
S.Yu. Favorov
Keyword(s):  
Uniqueness Theorem ◽  
Real Axis ◽  
Almost Periodic ◽  
Periodic Measure ◽  
Locally Compact ◽  
The Real ◽  
Approach Infinity ◽  
The Masses ◽  
Lca Groups

We show that if points of supports of two discrete ”not very thick” Fourier transformable measures on locally compact abelian (LCA) groups tend to one another at infinity and the same is true for the masses at these points, then these measures coincide. The result is valid for discrete almost periodic measures on LCA groups too. Also, we show that the result is false for some discrete ”thick” measures. To do this, we construct a discrete almost periodic measure on the real axis, whose masses at the points of support tend to zero as these points approach infinity.

Semidirect Product Compactifications

1983 ◽  
Vol 35 (1) ◽  
pp. 1-32
Author(s):  
F. Dangello ◽  
R. Lindahl
Keyword(s):  
Direct Product ◽  
Semidirect Product ◽  
Topological Semigroup ◽  
Sufficient Conditions ◽  
Almost Periodic Functions ◽  
Almost Periodic ◽  
Periodic Functions ◽  
Topological Semigroups ◽  
Weakly Almost Periodic ◽  
Necessary And Sufficient

1. Introduction. K. Deleeuw and I. Glicksberg [4] proved that if S and T are commutative topological semigroups with identity, then the Bochner almost periodic compactification of S × T is the direct product of the Bochner almost periodic compactifications of S and T. In Section 3 we consider the semidirect product of two semi topological semigroups with identity and two unital C*-subalgebras and of W(S) and W(T) respectively, where W(S) is the weakly almost periodic functions on S. We obtain necessary and sufficient conditions and for a semidirect product compactification of to exist such that this compactification is a semi topological semigroup and such that this compactification is a topological semigroup. Moreover, we obtain the largest such compactifications.

scholarly journals More On the countability index and the density index of S(X)

1990 ◽  
Vol 33 (1) ◽  
pp. 159-164
Author(s):  
K. D. Magill
Keyword(s):  
Finite Number ◽  
Topological Semigroup ◽  
Hausdorff Space ◽  
Extension Property ◽  
Dimensional Subspace ◽  
Countable Subset ◽  
Compact Open Topology ◽  
Locally Compact ◽  
Density Index ◽  
Locally Compact Hausdorff Space

The countability index, C(S), of a semigroup S is the smallest integer n, if it exists, such that every countable subset of S is contained in a subsemigroup with n generators. If no such integer exists, define C(S) = ∞. The density index, D(S), of a topological semigroup S is the smallest integer n, if it exists, such that S contains a dense subsemigroup with n generators. If no such integer exists, define D(S) = ∞. S(X) is the topological semigroup of all continuous selfmaps of the locally compact Hausdorff space X where S(X) is given the compact-open topology. Various results are obtained about C(S(X)) and D(S(X)). For example, if X consists of a finite number (< 1) of components, each of which is a compact N-dimensional subspace of Euclidean Nspace and has the internal extension property and X is not the two point discrete space. Then C(S(X)) exceeds two but is finite. There are additional results for C(S(X)) and similar results for D(S(X)).

scholarly journals Induction for Banach Algebras, Groupoids and KKban

2009 ◽  
Vol 4 (3) ◽  
pp. 405-468 ◽  
Author(s):  
Walther Paravicini
Keyword(s):  
Banach Algebra ◽  
Banach Algebras ◽  
The Other ◽  
Locally Compact ◽  
Morita Equivalent

AbstractGiven two equivalent locally compact Hausdorff groupoids, We prove that the Bost conjecture with Banach algebra coefficients is true for one if and only if it is true for the other. This also holds for the Bost conjecture with C*- coefficients. To show these results, the functoriality of Lafforgue's KK-theory for Banach algebras and groupoids with respect to generalised morphisms of groupoids is established. It is also shown that equivalent groupoids have Morita equivalent L1-algebras (with Banach algebra coefficients).

Mackey duals and almost shrinking bases

1973 ◽  
Vol 74 (1) ◽  
pp. 73-81 ◽  
Author(s):  
N. J. Kalton
Keyword(s):  
Banach Space ◽  
Weak Topology ◽  
Norm Topology ◽  
Weak Basis ◽  
Mackey Topology ◽  
Dual Sequence

Suppose (en) is a basis of a Banach space E, and that (e′n) is the dual sequence in E′. Then if (e′n) is a basis of E′ in the norm topology (i.e. (en) is shrinking) it follows that E′ is norm separable: it is easy to give examples of spaces E for which this is not so. Therefore there are plenty of spaces which cannot have a shrinking basis. This leads one to consider whether it might not be reasonable to replace the norm topology on E′ by one which is always separable (provided E is separable). Of course, the weak*-topology σ(E′, E) is one possibility (Köthe (17), p. 259); then it is trivial that (e′n) is a weak*-basis of E′. However, if the weak*-topology is separable, then so is the Mackey topology τ(E′, E) on E′, and so we may ask whether (e′n) is a basis of (E′,τ(E′, E)).

Algebras of measures on C-distinguished topological semigroups

1978 ◽  
Vol 84 (2) ◽  
pp. 323-336 ◽  
Author(s):  
H. A. M. Dzinotyiweyi
Keyword(s):  
Total Variation ◽  
Topological Semigroup ◽  
Continuous Mapping ◽  
Continuous Functions ◽  
Compact Set ◽  
Locally Compact ◽  
Radon Measures ◽  
Topological Semigroups ◽  
Bounded Complex ◽  
Complex Valued

Let S be a (jointly continuous) topological semigroup, C(S) the set of all bounded complex-valued continuous functions on S and M (S) the set of all bounded complex-valued Radon measures on S. Let (S) (or (S)) be the set of all µ ∈ M (S) such that x → │µ│ (x-1C) (or x → │µ│(Cx-1), respectively) is a continuous mapping of S into ℝ, for every compact set C ⊆ S, and . (Here │µ│ denotes the measure arising from the total variation of µ and the sets x-1C and Cx-1 are as defined in Section 2.) When S is locally compact the set Ma(S) was studied by A. C. and J. W. Baker in (1) and (2), by Sleijpen in (14), (15) and (16) and by us in (3). In this paper we show that some of the results of (1), (2), (14) and (15) remain valid for certain non-locally compact S and raise some new problems for such S.

A decomposition theorem for locally compact groups

2019 ◽  
Vol 26 (1) ◽  
pp. 29-33
Author(s):  
Sanjib Basu ◽  
Krishnendu Dutta
Keyword(s):  
Compact Group ◽  
Lebesgue Point ◽  
Decomposition Theorem ◽  
Locally Compact Group ◽  
The Other ◽  
Locally Compact Groups ◽  
Compact Groups ◽  
Topological Groups ◽  
Locally Compact ◽  
Interesting Connection

Abstract We prove that, under certain restrictions, every locally compact group equipped with a nonzero, σ-finite, regular left Haar measure can be decomposed into two small sets, one of which is small in the sense of measure and the other is small in the sense of category, and all such decompositions originate from a generalised notion of a Lebesgue point. Incidentally, such class of topological groups for which this happens turns out to be metrisable. We also observe an interesting connection between Luzin sets in such spaces and decompositions of the above type.

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