Let  be the configuration space of planar -gons having side lengths  and  modulo isometry group. For generic , the cohomology ring  has a form  where  is the first Stiefel-Whitney class of a certain regular -cover  and the ideal  is in general big. For generic , we determine the number  such that  but .
['Yasuhiko Kamiyama', 'Kazufumi Kimoto']
The Height of a Class in the Cohomology Ring of Polygon Spaces