Abstract For every one-relator monoid $$M = \langle A \mid u=v \rangle $$ M = ? A ? u v ? with $$u, v \in A^*$$ , ? <mml:mo...

In this paper we address the issue of uniformly positive scalar curvature on noncompact 3-manifolds. In particular we show that the Whitehead manifold lacks such a metric, and in fact that R3 is the only contractible noncompact 3-manifold with a metric of uniformly positive scalar curvature. We also describe contractible noncompact manifolds of higher dimension exhibiting this curvature phenome...

We show that a small neighborhood of a closed symplectic submanifold in a geometrically bounded aspherical symplectic manifold has nonvanishing symplectic homology. As a consequence, we establish the existence of contractible closed characteristics on any thickening of the boundary of the neighborhood. When applied to twisted geodesic flows on compact symplectically aspherical manifolds, this i...

Previously the authors characterized the 3-connected graphs with a Hamilton path containing only two contractible edges. In this paper we extend this result by showing that if a 3-connected graph has a diameter containing only two contractible edges, then that diameter is a Hamilton path. INTRODUCTION AND TERMINOLOGY All graphs in this paper are finite, undirected and simple. Let G be a 3-conne...

A dilatation structure on a metric space, is a notion in between a group and a differential structure. The basic objects of a dilatation structure are dilatations (or contractions). The axioms of a dilatation structure set the rules of interaction between different dilatations. There are two notions of linearity associated to dilatation structures: the linearity of a function between two dilata...

Many quality dimensions are hard to contract upon and are at risk of degradation when the service is procured rather than produced in-house. On the other hand, procurement may foster performance-improving innovation. We assemble a large data set on elderly care services in Sweden for the 1990-2009 period, including survival rates, our measure of non-contractible quality, and indicators of subje...

Open forms of global constraints allow the addition of new variables to an argument during the execution of a constraint program. Such forms are needed for difficult constraint programming problems where problem construction and problem solving are interleaved. However, in general, filtering that is sound for a global constraint can be unsound when the constraint is open. This paper provides a ...

We show that a small neighborhood of a closed symplectic submanifold in a geometrically bounded aspherical symplectic manifold has nonvanishing symplectic homology. As a consequence, we establish the existence of contractible closed characteristics on any thickening of the boundary of the neighborhood. When applied to twisted geodesic flows on compact symplectically aspherical manifolds, this i...