Rigidity Conjectures

Abstract: We prove several rigidity results for corona $C^*$-algebras and \v{C}ech-Stone remainders under the assumption of Forcing Axioms. In particular, we prove that a strong version of Todor\v{c}evi\'c's $\OCA$ and Martin's Axiom at level $\aleph_1$ imply: (i) that if $X$ and $Y$ are locally compact second countable topological spaces, then all homeomorphisms between $\beta X\setminus X$ and $\beta Y\setminus Y$ are induced by homeomorphisms between cocompact subspaces of $X$ and $Y$; (ii) that all automorphisms of the corona algebra of a separable $C^*$-algebra are trivial in a topological sense; (iii) that if $A$ is a unital separable infinite-dimensional $C^*$-algebra, the corona algebra of $A\otimes \mathcal K(H)$ does not embed into the Calkin algebra. All these results do not hold under the Continuum Hypothesis.