The trace equivalence of BPP was shown to be undecidable by Hirshfeld. We show that the trace equivalence remains undecidable even if the number of labels is restricted to two. The undecidability result holds also for the simulation of two-label BPP processes. These results imply undecidability of some behavioral type systems for the π-calculus.

We describe the inner models with representatives in all equivalence classes of thin equivalence relations in a given projective pointclass of even level assuming projective determinacy. These models are characterized by their correctness and the property that they correctly compute the tree from the appropriate scale. The main lemma shows that the tree from a scale can be reconstructed in a ge...

We give a list of canonical equivalence relations on discrete nets of the positive unit sphere of c0. This generalizes results of W. T. Gowers [1] and A. D. Taylor [5].

We define the A4-structure of a graph G to be the 4-uniform hypergraph on the vertex set of G whose edges are the vertex subsets inducing 2K2, C4, or P4. We show that perfection of a graph is determined by its A4-structure. We relate the A4structure to the canonical decomposition of a graph as defined by Tyshkevich [Discrete Mathematics 220 (2000) 201-238]; for example, a graph is indecomposabl...

This paper presents and philosophically assesses three types of results on the observational equivalence of continuous-time measure-theoretic deterministic and indeterministic descriptions. The first results establish observational equivalence to abstract mathematical descriptions. The second results are stronger because they show observational equivalence between deterministic and indeterminis...

This paper considers the real-valued random variables X1, . . . , Xn with corresponding distributions F1, . . . , Fn, such that X1, . . . , Xn admit some dependence structure and n(F1 + · · · + Fn) belongs to the class dominatedly varying-tailed distributions. The weak equivalence relations between the quantities P(Sn > x), P(max{X1, . . . , Xn} > x), P(max{S1, . . . , Sn} > x) and ∑n k=1 Fk(x)...

Subtyping in first order object calculi is studied with respect to the logical semantics obtained by identifying terms that satisfy the same set of predicates, as formalized through an assignment system. It is shown that equality in the full first order ς-calculus is modelled by this notion, which on turn is included in a Morris style contextual equivalence.