This open access book provides an accessible introduction to the highly debated topic of irregular migration in a European perspective. Free online read.

We introduce matchmaking as a specific setting for similarity assessment. While in many domains similarity assessment is between pairs of entities with equal status, this is not true for matchmaking in general. Usually, in matchmaking there exists a source request which triggers search for the most similar set of available entities. Whether an entity is acceptable depends highly on the applicat...

Via a computer search, Altshuler and Steinberg found that there are 1296 + 1 combinatorial 3-manifolds on nine vertices, of which only one is non-sphere. This exceptional 3-manifold K 9 triangulates the twisted S -bundle over S . It was first constructed by Walkup. In this paper, we present a computer-free proof of the uniqueness of this non-sphere combinatorial 3-manifold. As opposed to the co...

In 1987, Kalai proved that stacked spheres of dimension d ≥ 3 are characterised by the fact that they attain equality in Barnette’s celebrated Lower Bound Theorem. This result does not extend to dimension d = 2. In this article, we give a characterisation of stacked 2-spheres using what we call the separation index. Namely, we show that the separation index of a triangulated 2-sphere is maximal...