Characterizations of generalized polygons and opposition in rank 2 twin buildings
نویسندگان
چکیده
In this paper, we characterize the natural opposition relation on the set of flags of a generalized polygon. We also investigate when a certain relation on any rank 2 geometry of finite diameter is equivalent to the opposition relation in a generalized polygon. As a consequence we obtain a new definition of generalized polygons. Finally, we also characterize the opposition relation in twin trees, which are the analogues of polygons with infinite diameter. Mathematics Subject Classification (2000): 51E24, 51E12.
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