Local spectral synthesis on Abelian groups

We say that a complex valued function defined on an Abelian group G is a local polynomial, if its restriction to every finitely generated subgroup of G is a polynomial. We prove that local spectral synthesis (that is, spectral synthesis using local polynomials instead of polynomials) holds on every Abelian group having countable torsion free rank. More precisely, there is a cardinal ω ₁≦κ≦2 ^ω such that local spectral synthesis holds on an Abelian group G if and only if the torsion free rank of G is less than κ.     

The failure of spectral synthesis on some types of discrete Abelian groups

The problem of spectral synthesis on arbitrary Abelian groups is solved in the negative.     

A generalized principal ideal theorem

The main theorem of this article is an extension of the generalized principal ideal theorem for ideals in Noetherian rings. Instead of requiring the rings to be Noetherian, some natural requirements are imposed on the chains of prime ideals under consideration. The standard (Noetherian) version of the generalized principal ideal theorem is deduced as a corollary and two other applications are presented.     

Harmonic analysis on discrete Abelian groups

Let be an Abelian group and let denote the linear space of all complex-valued functions defined on equipped with the product topology. We prove that the following are equivalent.

(i) Every nonzero translation invariant closed subspace of contains an exponential; that is, a nonzero multiplicative function.

(ii) The torsion free rank of is less than the continuum.

     

On the Heyde theorem for some locally compact Abelian groups

According to the well-known Heyde theorem Gaussian distribution on the real line is characterized by the symmetry of the conditional distribution of one linear form in n independent random variables given another. For n = 2 we prove analogs of this theorem in the case when random variables take values in a locally compact Abelian group X, and coefficients of the linear forms are topological automorphisms of the group X.     

Commutative ideal extensions of Abelian groups

No Abstract. May 26, 1999     

A theorem on direct expansions of Abelian groups

The following assertion is proved: if the basis subgroups of the periodic part t(G) of a non-denumerable Abelian group G have the same cardinality as G, then each of the subgroups contains, as a subgroup of the same cardinality as G, a direct component of G. The restriction on the cardinality of G is essential.Translated from Matematicheskie Zametki, Vol. 14, No. 6, pp. 879–884, December, 1973.     

An addition theorem for finite Abelian groups

If g₁, g₂, …, g_2n?1 is a sequence of 2n ? 1 elements in an Abelian group G of order n, it is known that there are n distinct indices i₁, i₂, …, i_n such that 0 = g_i1 + g_i2 + ? + g_in. In this paper a suitably general condition on the sequence is given which insures that every element g in G has a representation g = g_i1 + g_i2 + ? + g_in as the sum of n terms of the sequence.     

On the spectral mapping theorem for one-parameter groups of operators

Let A be the generator of a strongly continuous nonquasianatytic oneparameter group of operators U(t) (A, in general, is unbounded). In this case one proves a spectral mapping theorem in the following form:. The proof is based on the theory of operators with separable spectrum.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova Akademii Nauk SSSR, Vol. 178, pp. 146–150, 1989.     

On the Shunkov groups acting freely on Abelian groups

We prove the existence of a locally finite periodic part in every rank 1 Shunkov group with solvable finite subgroups, in every Shunkov group acting freely on an abelian group, and in the groups of affine transformations of neardomains with finite elements.     

The Heyde theorem for locally compact Abelian groups

We prove a group analogue of the well-known Heyde theorem where a Gaussian measure is characterized by the symmetry of the conditional distribution of one linear form given another. Let X be a locally compact second countable Abelian group containing no subgroup topologically isomorphic to the circle group T, G be the subgroup of X generated by all elements of order 2, and Aut(X) be the set of all topological automorphisms of X. Let αj,βj∈Aut(X), j=1,2,…,n, n?2, such that for all i≠j. Let ξj be independent random variables with values in X and distributions μj with non-vanishing characteristic functions. If the conditional distribution of L₂=β₁ξ₁+?+βnξn given L₁=α₁ξ₁+?+αnξn is symmetric, then each μj=γj∗ρj, where γj are Gaussian measures, and ρj are distributions supported in G.     

On the factorization of Abelian groups

In this note we consider a conjecture made by Professor de Bruijn and subsequent generalizations of this conjecture. We show by using constructions of his that in a certain sense these generalizations are the best possible. A survey of these known results is presented. Finally some new results of this kind are given.