Amenable-group Z-stability and the small boundary property

Establish that, for every free minimal action of an amenable group on a compact metrizable space, Z-stability of the crossed product is equivalent to the small boundary property.

Background

The survey identifies Z-stability as the remaining dynamical condition needed for classifiability of crossed products associated to free minimal amenable actions. Although examples show that Z-stability can fail, the conjecture proposes that its precise dynamical characterization is the small boundary property.

References

Conjecture 1.0.1 (Amenable groups). Let G ↷ X be a free, minimal, action of an amenable group. Then the following are equivalent:

— Classifiability of crossed products  (2610.06586 - Gardella, 5 Oct 2026) in Conjecture 1.0.1, Chapter 1, pp. 2–3

Conjecture 4.4.6. Let G be amenable and let G ↷ X be a free, minimal dynamical system. Then the following are equivalent:

— Classifiability of crossed products  (2610.06586 - Gardella, 5 Oct 2026) in Conjecture 4.4.6, Section 4.4, p. 39