ar X iv : 0 90 2 . 22 20 v 1 [ m at h . D G ] 1 2 Fe b 20 09 CLASSIFYING CLOSED 2 - ORBIFOLDS WITH EULER CHARACTERISTICS

نویسنده

  • BRADFORD TAYLOR
چکیده

We determine the extent to which the collection of Γ-Euler-Satake characteristics classify closed 2-orbifolds. In particular, we show that the closed, connected, effective, orientable 2-orbifolds are classified by the collection of Γ-EulerSatake characteristics corresponding to free or free abelian Γ and are not classified by those corresponding to any finite collection of finitely generated discrete groups. Similarly, we show that such a classification is not possible for non-orientable 2orbifolds and any collection of Γ, nor for noneffective 2-orbifolds. As a corollary, we generate families of orbifolds with the same Γ-Euler-Satake characteristics in arbitrary dimensions for any finite collection of Γ; this is used to demonstrate that the Γ-Euler-Satake characteristics each constitute new invariants of orbifolds.

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تاریخ انتشار 2009