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Research Report MRR01-013

Weak* Properties of Weighted Convolution Algebras

Sandy Grabiner

Abstract: Suppose that L1(\omega) is a weighted convolution algebra on R+ = [0, 1) with the weight \omega(t)$ normalized so that the corresponding space M(\omega) of measures is the dual space of the space C0(1/\omega) of continuous functions. Suppose that $\phi : L1(\omega) -> L1(\omega') is a continuous nonzero homomorphism, where L1(\omega') is also a convolution algebra. If L1(\omega) * f is norm dense in L1(\omega), we show that L1(\omega') * \phi(f) is (relatively) weak* dense in L1(\omega'), and we identify the norm closure of L1(\omega') * \phi(f) with the convergence set for a particular semigroup. When \phi is weak* continuous it is enough for L1(\omega) * f to be weak* dense in L1(\omega). We also give sufficient conditions and characterizations of weak* continuity of \phi. In addition, we show that, for all nonzero f in L1(\omega), the sequence fn / || fn || converges weak* to 0. When \omega is regulated, fn+1 / || fn || converges to 0 in norm.

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