We present an explicit combinatorial realization of the commutor in the category of crystals which was first studied by Henriques and Kamnitzer. Our realization is based on certain local moves defined by van Leeuwen.

Bart van Leeuwen [email protected] / @semanticfire Bart van Leeuwen combines his 15 years firefighting experience with 17 years of netage.nl ownership. This combination allows him to highlight a new perspective on operational information delivery. With the ever larger amount of available data and changes in tactical approaches to firefighting new and fresh thinking is needed. As a " outside the bo...

Recently considerable interest has been shown in questions concerning the complexity of the membership problem for various types of L systems3 In van Leeuwen (1975a) it is shown that there is an E T O L system G such that the set L(G) is ~/ '~-complete . Opatrn3~ and Culik (1975) showed that EOL membership could be determined by a D T I M E (n 4) algorithm, and Sudborough (1976) gave a DSPACE((...

Karp, R. M., and V. Ramachandran. 1990. Parallel algorithms for shared-memory machines. In Handbook of Theoretical Computer Science, volume A, Algorithms and Complexity, edited by J. van Leeuwen. Cambridge, MA: MIT Press/Elsevier. Kearns, M. J., and U. V. Vazirani. 1994. An Introduction to Computational Learning Theory. Cambridge, MA: MIT Press. Kitaev, A., A. Shen, and M. Vyalyi. 2002. Classic...

We give a polynomial-time approximation scheme for the unique unit-square coverage problem: given a set of points and a set of axis-parallel unit squares, both in the plane, we wish to find a subset of squares that maximizes the number of points contained in exactly one square in the subset. Erlebach and van Leeuwen (2008) introduced this problem as the geometric version of the unique coverage ...