Rapport sur la géométrie par morceaux
Les espaces de bracelets et les complexes de Stasheff
Models for actions of certain groupoids
Area preserving pl homeomorphisms and relations in
To any compactly supported, area preserving, piecewise linear homeomorphism of the plane is associated a relation in of the smallest field whose elements are needed to write the homeomorphism. Using a formula of J. Morita, we show how to calculate the relation, in some simple cases. As applications, a “reciprocity” formula for a pair of triangles in the plane, and some explicit elements of torsion in of certain function fields are found.
An acyclic extension of the braid group.
Forte connexité des complexes polyèdraux
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