Abstract
We introduce the concept of approximately invertible elements in non-unital normed algebras which is, on one side, a natural generalization of invertibility when having approximate identities at hand, and, on the other side, it is a direct extension of topological invertibility to non-unital algebras. Basic observations relate approximate invertibility with concepts of topological divisors of zero and density of (modular) ideals. We exemplify approximate invertibility in the group algebra, Wiener algebras, and operator ideals. For Wiener algebras with approximate identities (in particular, for the Fourier image of the convolution algebra), the approximate invertibility of an algebra element is equivalent to the property that it does not vanish. We also study approximate invertibility and its deeper connection with the Gelfand and representation theory in non-unital abelian Banach algebras as well as abelian and non-abelian C*-algebras.
Translated title of the contribution | Elementos aproximadamente invertibles en álgebras normadas no unitarias |
---|---|
Original language | English |
Article number | 126986 |
Journal | Journal of Mathematical Analysis and Applications |
Volume | 523 |
Issue number | 1 |
DOIs | |
State | Published - 1 Jul 2023 |
Keywords
- Approximate identity
- Approximate invertibility
- Maximal modular ideal
- Non-unital Banach algebra
- Non-unital topological algebra
- Principal ideal