A1-connected components of schemes

A1-homotopy theory of schemes

Twinless Strongly Connected Components

Tarjan [9], describes how depth first search can be used to identify Strongly Connected Components (SCC) of a directed graph in linear time. It is standard to study Tarjan’s SCC algorithm in most senior undergraduate or introductory graduate computer science algorithms courses. In this paper we introduce the concept of a twinless strongly connected component (TSCC) of a directed graph. Loosely ...

Quasi-4-Connected Components

We introduce a new decomposition of a graphs into quasi-4-connected components, where we call a graph quasi-4-connected if it is 3-connected and it only has separations of order 3 that separate a single vertex from the rest of the graph. Moreover, we give a cubic time algorithm computing the decomposition of a given graph. Our decomposition into quasi-4-connected components refines the well-kno...

Concurrent determination of connected components

The design is described of a parallel version of Tarjan’s algorithm for the determination of equivalence classes in graphs that represent images. Distribution of the vertices of the graph over a number of processes leads to a message passing algorithm. The algorithm is mapped to a shared-memory architecture by means of POSIX threads. It is applied to the determination of connected components in...

Non-connected Toric Hilbert Schemes

We construct small (50 and 26 points, respectively) point sets in dimension 5 whose graphs of triangulations are not connected. These examples improve our construction in J. Amer. Math. Soc. 13:3 (2000), 611–637 not only in size, but also in that their toric Hilbert schemes are not connected either, a question left open in that article. Additionally, the point sets can easily be put into convex...