Gardens of Eden and amenability on cellular automata
We investigate the amenability and its related homological notions for a class of -upper triangular matrix algebra, say , where is a Banach algebra equipped with a nonzero character. We show that is pseudo-contractible (amenable) if and only if is singleton and is pseudo-contractible (amenable), respectively. We also study pseudo-amenability and approximate biprojectivity of .
We tackle R. V. Kadison’s similarity problem (i.e. any bounded representation of any unital C*-algebra is similar to a *-representation), paying attention to the class of C*-unitarisable groups (those groups G for which the full group C*-algebra C*(G) satisfies Kadison’s problem) and thereby we establish some stability results for Kadison’s problem. Namely, we prove that inherits the similarity problem from those of the C*-algebras A and B, provided B is also nuclear. Then we prove that G/Γ is...