Class G, and a unification problem

Unification in a Class of Permutative Theories

It has been proposed in [1] to perform deduction modulo leaf permutative theories, which are notoriously hard to handle directly in equational theorem proving. But unification modulo such theories is a difficult task, not tackled in [1]; a subclass of flat equations has been considered only recently, in [2]. Our emphasis on group theoretic structures led us in [6] to the definition of a more ge...

The Intersection Type Unification Problem

The intersection type unification problem is an important component in proof search related to several natural decision problems in intersection type systems. It is unknown and remains open whether the unification problem is decidable. We give the first nontrivial lower bound for the problem by showing (our main result) that it is exponential time hard. Furthermore, we show that this holds even...

Relation between Unification Problem and Intruder Deduction Problem

Intruder deduction problem constitutes the first step in cryptographic protocols verification for a passive intruder. In the case of an active intruder, we know that undecidability of the unification problem implies undecidability of the secrecy problem. In this paper, we analyze the link between the unification problem and the intruder deduction problem. Through examples using equational theor...

2 Sets and the Set Unification Problem

On a Problem of G . G . Lorentz

Let C(B) denote the space of real-valued continuous functions on B. At the conference Harmonic Analysis and Approximations held at Nor Amberd in Armenia in September, 1998, the following general problem was posed by Professor George G. Lorentz. Find conditions on finite dimensional subspaces U and V so that U/V is a unicity set in the problem of best uniform approximation to elements of C(B). I...