Some characterizations of \(Q\)-algebras. (English) Zbl 0998.46020
Among other results the authors show that a unital topological algebra \(A\) is a \(Q\)-algebra (the group of invertible elements is open) iff the “spectral map” \(x\to\sigma(x)\) is upper semicontinuous, or, iff the spectral radius \(\rho(x)\) is continuous at \(0\).
Reviewer: Wiesław Tadeusz Zelazko (Warszawa)
MSC:
46H20 | Structure, classification of topological algebras |
46H05 | General theory of topological algebras |