We develop a homology of vertex groups as a tool for studying orbifolds and orbifold cobordism and its torsion. To a pair (G,H) of conjugacy classes of degree-n and degree-(n − 1) finite subgroups of SO(n) and SO(n − 1) we associate the parity with which H occurs up to O(n) conjugacy as a vertex group in the orbifold Sn−1∕G. This extends to a map dn: βn → βn−1 between the Z2 vector spaces whose bases are all such conjugacy classes in SO(n) and then SO(n − 1). Using orbifold graphs, we prove d: β → β is a differential and defines a homology, ℋ∗. We develop a map s: β∗−→ β∗+1− for a subcomplex of groups which admit orientation-reversing automorphisms. We then look at examples and algebraic properties of d and s, including that d is a derivation. We prove that the natural map ψ between the set of diffeomorphism classes of closed, locally oriented n–orbifolds and βn maps into kerdn and that this map is onto kerdn for n ≤ 4. We relate d to orbifold cobordism and surgery and show that ψ quotients to a map between oriented orbifold cobordism and ℋ∗.
Keywords: orbifolds, cobordism, vertex groups, finite subgroups of SO(n)
Druschel, Kimberly  1
@article{10_2140_agt_2015_15_169,
author = {Druschel, Kimberly},
title = {Oriented orbifold vertex groups and cobordism and an associated differential graded algebra},
journal = {Algebraic and Geometric Topology},
pages = {169--190},
year = {2015},
volume = {15},
number = {1},
doi = {10.2140/agt.2015.15.169},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2015.15.169/}
}
TY - JOUR AU - Druschel, Kimberly TI - Oriented orbifold vertex groups and cobordism and an associated differential graded algebra JO - Algebraic and Geometric Topology PY - 2015 SP - 169 EP - 190 VL - 15 IS - 1 UR - http://geodesic.mathdoc.fr/articles/10.2140/agt.2015.15.169/ DO - 10.2140/agt.2015.15.169 ID - 10_2140_agt_2015_15_169 ER -
%0 Journal Article %A Druschel, Kimberly %T Oriented orbifold vertex groups and cobordism and an associated differential graded algebra %J Algebraic and Geometric Topology %D 2015 %P 169-190 %V 15 %N 1 %U http://geodesic.mathdoc.fr/articles/10.2140/agt.2015.15.169/ %R 10.2140/agt.2015.15.169 %F 10_2140_agt_2015_15_169
Druschel, Kimberly. Oriented orbifold vertex groups and cobordism and an associated differential graded algebra. Algebraic and Geometric Topology, Tome 15 (2015) no. 1, pp. 169-190. doi: 10.2140/agt.2015.15.169
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