
Let \({\mathfrak A}\) be a commutative Banach algebra with dual \({\mathfrak A}^*\). For \(\phi \in A^*\), define \({\breve \phi}\)(a,b)\(=\phi (ab)- \phi (a)\phi (b)\), and call \(\phi\delta\)-multiplicative iff \(\| {\breve \phi}\| \leq \delta\). \({\mathfrak A}\) is an algebra in which approximately multiplicative functionals are near multiplicative (AMNM) if for each \(\epsilon >0\), there is \(\delta >0\) such that \(\inf \{\| \phi -\psi \|:\psi\) is a \(character\}<\epsilon\) whenever \(\phi\) in \({\mathfrak A}^*\) is \(\delta\)-multiplicative. The author studies these entities and shows that AMNM algebras include the well-known examples (finite dimensional, \(C_ 0(X)\), \(L^ 1(G)\), \(\ell^ 1({\mathbb{Z}})\), disc algebra), but not all. A result of Gleason about multiplicativeness of functions with range contained in the spectrum is studied in a more general context.
Structure and classification of commutative topological algebras, General theory of commutative topological algebras, an algebra in which approximately multiplicative functionals are near multiplicative, AMNM algebras
Structure and classification of commutative topological algebras, General theory of commutative topological algebras, an algebra in which approximately multiplicative functionals are near multiplicative, AMNM algebras
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