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On compact normal semigroups

Published online by Cambridge University Press:  20 January 2009

S. T. L. Choy
Affiliation:
Department of Mathematics, King's College, Aberdeen
B. Dummigan
Affiliation:
Department of Mathematics, King's College, Aberdeen
J. Duncan
Affiliation:
Department of Mathematics, King's College, Aberdeen
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A semigroup S is said to be normal if aS = Sa for each a in S. Thus the class of normal semigroups includes the class of groups and the class of Abelian semigroups. Given a compact semigroup S we write P(S) for the convolution semigroup of probability regular Borel measures on S. In (3), Theorem 7, Lin asserts that a compact semigroup S is normal if and only if P(S) is normal. We show in this paper that Lin's result is false. In fact, if S is the union of subsemigroups each of which has an identity element, we show that P(S) is normal if and only if S is Abelian. Thus any compact non-Abelian group contradicts Lin's result. What Lin's argument does establish is that if P(S) is normal then S is normal, and if S is normal then μP(S) = P(S)μ for each point mass measure μ.

Type
Research Article
Copyright
Copyright © Edinburgh Mathematical Society 1969

References

REFERENCES

(1) Collins, H. S.Idempotent measures on compact semigroups, Proc. Amer. Math. Soc. 13 (1963), 442446.CrossRefGoogle Scholar
(2) Glicksberg, I.Convolution semigroups of measures, Pacific J. Math. 9 (1959), 5167.CrossRefGoogle Scholar
(3) Lin, Y. F.Not necessarily Abelian convolution semigroups of probability measures, Math. Zeitschrift, 91 (1966), 300307.CrossRefGoogle Scholar