A Kadec-Pelczyński dichotomy-type theorem for preduals of JBW*-algebras

Preduals of semigroup algebras

For a locally compact group G, the measure convolution algebra M(G) carries a natural coproduct. In previous work, we showed that the canonical predual C0(G) of M(G) is the unique predual which makes both the product and the coproduct on M(G) weak∗-continuous. Given a discrete semigroup S, the convolution algebra l(S) also carries a coproduct. In this paper we examine preduals for l(S) making b...

Operator Algebras with Unique Preduals

We show that every free semigroup algebras has a (strongly) unique Banach space predual. We also provide a new simpler proof that a weak-∗ closed unital operator operator algebra containing a weak-∗ dense subalgebra of compact operators has a unique Banach space predual.

Toward a Dichotomy Theorem for Polynomial Evaluation

A dichotomy theorem for counting problems due to Creignou and Hermann states that or any finite set S of logical relations, the counting problem #SAT(S) is either in FP, or #P-complete. In the present paper we study polynomial evaluation from this dichotomic point of view. We show that the “hard” cases in the Creignou-Hermann theorem give rise to VNP-complete families of polynomials, and we giv...

A Dichotomy Theorem for Regular Types

A dichotomy theorem for circular colouring reconfiguration

Let p and q be positive integers with p/q ≥ 2. The “reconfiguration problem” for circular colourings asks, given two (p, q)-colourings f and g of a graph G, is it possible to transform f into g by changing the colour of one vertex at a time such that every intermediate mapping is a (p, q)-colouring? We show that this problem can be solved in polynomial time for 2 ≤ p/q < 4 and that it is PSPACE...