In this article we study locally compact abelian (LCA) groups from the viewpoint of derived categories, using that their category is quasi-abelian in the sense of J.-P. Schneiders. We define a well-behaved derived Hom-complex with values in the derived category of Hausdorff topological abelian groups. Furthermore we introduce a smallness condition for LCA groups and show that such groups have a...

This is a literal reproduction of the 1983 report [55] by Hans G. Feichtinger, with only the obvious typos being corrected, one additional section and minor extra footnotes. Only few symbols have been changed to more standard ones, e.g. for the translation operator (which was L y , following Hans Reiter) has been replaced by T y , and instead of K(G) we write C c (G) now. We hope that by adding...

The problem of global optimization of M incoherent phase signals in N complex dimensions is formulated. Then, by using the geometric approach of Landau and Slepian, conditions for optimality are established for N 2, and the optimal signal sets are determined for M 2, 3, 4, 6 and 12. The method is the following: The signals are assumed to be equally probable and to have equal energy, and thus ar...

The notion of a tensor product of topological groups and modules is important in theory of topological groups, algebraic number theory. The tensor product of compact zero-dimensional modules over a pseudocompact algebra was introduced in [B] and for the commutative case in [GD], [L]. The notion of a tensor product of abelian groups was introduced in [H]. The tensor product of modules over commu...

We introduce model sets in arbitrary locally compact second countable (lcsc) groups, generalizing Meyer’s definition of a model set in a locally compact abelian group. We then provide a new formulation of diffraction theory, which unlike the classical formulation does not involve Følner sets and thus generalizes to point sets in non-amenable lcsc groups. We focus on the case of lcsc groups admi...

For a locally compact abelian group $G$, J. L. Taylor (1971) gave complete characterization of invertible elements in the measure algebra $M(G)$. Using Fourier-Stieltjes transform, this can be carried out context algebras $B(G)$. We obtain latter for $B(G)$ certain classes groups, particular, many totally minimal groups and $ax+b$-group.

The objective of this paper is to construct wavelet packets associated with multiresolution analysis on locally compact Abelian groups. Moreover, from the collection of dilations and translations of the wavelet packets, we characterize the subcollections which form an orthonormal basis for L(G).

In this paper, we study the group Pext(C, A) for locally compact abelian (LCA) groups A and C. Sufficient conditions are established for Pext(C, A) to coincide with the first Ulm subgroup of Ext(C, A). Some structural information on pure injectives in the category of LCA groups is obtained. Letting C denote the class of LCA groups which can be written as the topological direct sum of a compactl...

Christensen has defined a generalization of the property of being of Haar measure zero to subsets of (abelian) Polish groups which need not be locally compact; a recent paper of Hunt, Sauer, and Yorke defines the same property for Borel subsets of linear spaces, and gives a number of examples and applications. The latter authors use the term “shyness” for this property, and “prevalence” for the...

In this paper, we show that for every locally compact abelian group G, the following statements are equivalent: (i) G contains no sequence {xn}n=0 such that {0} ∪ {±xn | n ∈ N} is infinite and quasiconvex in G, and xn −→ 0; (ii) one of the subgroups {g ∈ G | 2g = 0} and {g ∈ G | 3g = 0} is open in G; (iii) G contains an open compact subgroup of the form Z2 or Z κ 3 for some cardinal κ.