In this article we will present some problems that have weak symmetries. In contrast to a proper symmetry, a weak symmetry acts only on a subset of the variables and preserves the feasibility state only with respect to a subset of the constraints. Therefore, breaking weak symmetries with standard techniques would lead to a loss of solutions. This article presents also a modelling technique whic...

In this paper, we classify all generalized quadrangles weakly embedded of degree 2 in projective space. More exactly, given a (possibly infinite) generalized quadrangle Γ = (P,L, I ) and a map π from P (respectively L) to the set of points (respectively lines) of a projective space PG(V ), V a vector space over some skew field (not necessarily finite-dimensional), such that: (i) π is injective ...

We discuss the axioms for vertex algebras and their modules, using formal calculus. Following certain standard treatments, we take the Jacobi identity as our main axiom and we recall weak commutativity and weak associativity. We derive a third, companion property that we call “weak skew-associativity.” This third property in some sense completes an S3-symmetry of the axioms, which is related to...