The spectrum of the canonical operator in the noncommutative 2-torus Tθ depending on the parameter θ ∈ [0,1] © Douglas Hofstadter's butterfly. Licensed under ...

In operator algebras we are particularly interested in $\mathsf{C}^*$-algebra theory and its connections to other areas such as dynamical systems, group theory, topology, non-commutative geometry, and ...

In this article, we introduce the notion of polynomial demicompactness and we use it to give some results on Fredholm operators and to establish a fine description of some essential spectra of a ...