On T-sequences and characterized subgroups |
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Authors: | SS Gabriyelyan |
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Institution: | Department of Mathematics, Ben-Gurion University of the Negev, Beer-Sheva, P.O. 653, Israel |
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Abstract: | Let X be a compact metrizable abelian group and u={un} be a sequence in its dual group X∧. Set su(X)={x:(un,x)→1} and . Let G be a subgroup of X. We prove that G=su(X) for some u iff it can be represented as some dually closed subgroup Gu of . In particular, su(X) is polishable. Let u={un} be a T-sequence. Denote by the group X∧ equipped with the finest group topology in which un→0. It is proved that and . We also prove that the group generated by a Kronecker set cannot be characterized. |
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Keywords: | Characterized group T-sequence TB-sequence Dual group Polish group von Neumann radical Kronecker set |
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