Certain types of integrable non-linear PDEs (soliton equations) arise in differential geometry as compatibility conditions for the linear equations obeyed by frames adapted to surfaces in higher dimensional manifolds. In a number of situations, the construction of new solutions of the arising PDE relies on the existence of Bäcklund type transformations for the surfaces and on their permutabilit...

In this paper, we investigate automated proof construction in classical linear logic (CLL) by giving logical foundations for the design of proof search strategies. We propose common theoretical foundations for top-down, bottom-up and mixed proof search procedures with a systematic formalization of strategies construction using the notions of immediate or chaining composition or decomposition, d...

For distributive double p-algebras, a close connection is established between being congruence coherent and congruence regular. Every congruence regular distributive double p-algebra is congruence coherent. Even though every congruence coherent distributive double p-algebra that has either a non-empty core or finite range is congruence regular, an example is given that is congruence coherent bu...

In this paper we investigate some properties of congruences on ternary semigroups. We also define the notion of congruence on a ternary semigroup generated by a relation and we determine the method of obtaining a congruence on a ternary semigroup T from a relation R on T. Furthermore we study the lattice of congruences on a ternary semigroup and we show that this lattice is not generally modular...

To every morphism of X∗ a congruence fR on X ∗, called kernel congruence, and defined by ufRv iff f(u) = f(v) can be associated. We characterize morphisms having a commutative kernel congruence and, introducing the notion of the index of a morphism, we give a classification of the morphisms of X∗. Moreover, a congruence with special properties, called hp-congruence is considered; every kernel c...

9 The theory of chi processes with the mismatch operator is studied. Four congruence relations are investigated. These are late open congruence, early open congruence, ground congruence and 11 barbed congruence. The late and early open congruence relations are the chi calculus counterparts of the weak late and early congruence relations of pi calculus. Both turn out to be special cases 13 of th...