Density of mixing identity-plus-bilateral-shift perturbations

Determine whether the set of mixing operators \(\{I+B_w\in\mathcal{M}: w\in c_0(\mathbb{Z})\}\) is dense in \(\mathcal{M}\) endowed with the norm topology, where \(\mathcal{M}=\{I+B_w\in\mathcal{L}(\ell_p(\mathbb{Z})):w\in c_0(\mathbb{Z})\}\) and \(1<p<\infty\).

Background

For the norm-topologized family of identity-plus-bilateral-weighted-backward-shift operators, the paper establishes that weak mixing is typical, topological ergodicity is meager, and weak disjointness from a fixed hypercyclic operator is residual.

The paper does not determine whether the stronger property of mixing is dense in this concrete family. The unresolved question asks specifically about norm-density of mixing operators among all perturbations I+BwI+B_w with weights in c0(Z)c_0(\mathbb{Z}).

References

We end this section with the following natural question:

When X=\ell_p(\mathbb{Z}), 1< p<\infty and \mathcal{M}={I+B_w \colon w\in c_0(\mathbb{Z})}\subset (\mathcal{L} (X),|\cdot|), endowed with the norm topology, is {I+B_w \in \mathcal{M} \colon I+B_w \text{ is mixing } } dense in \mathcal{M}?

Typical dynamical properties of operators on $\ell_p$  (2609.10957 - Li et al., 10 Sep 2026) in End of Section 5