In this paper we define a QP1–valued class function on the mapping class group ℳg,2 of a surface Σg,2 of genus g with two boundary components. Let E be a Σg,2–bundle over a pair of pants P. Gluing to E the product of an annulus and P along the boundaries of each fiber, we obtain a closed surface bundle over P. We have another closed surface bundle by gluing to E the product of P and two disks.
The sign of our class function cobounds the 2–cocycle on ℳg,2 defined by the difference of the signature of these two surface bundles over P.
Sato, Masatoshi  1
@article{10_2140_agt_2008_8_1647,
author = {Sato, Masatoshi},
title = {A class function on the mapping class group of an orientable surface and the {Meyer} cocycle},
journal = {Algebraic and Geometric Topology},
pages = {1647--1665},
year = {2008},
volume = {8},
number = {3},
doi = {10.2140/agt.2008.8.1647},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2008.8.1647/}
}
TY - JOUR AU - Sato, Masatoshi TI - A class function on the mapping class group of an orientable surface and the Meyer cocycle JO - Algebraic and Geometric Topology PY - 2008 SP - 1647 EP - 1665 VL - 8 IS - 3 UR - http://geodesic.mathdoc.fr/articles/10.2140/agt.2008.8.1647/ DO - 10.2140/agt.2008.8.1647 ID - 10_2140_agt_2008_8_1647 ER -
%0 Journal Article %A Sato, Masatoshi %T A class function on the mapping class group of an orientable surface and the Meyer cocycle %J Algebraic and Geometric Topology %D 2008 %P 1647-1665 %V 8 %N 3 %U http://geodesic.mathdoc.fr/articles/10.2140/agt.2008.8.1647/ %R 10.2140/agt.2008.8.1647 %F 10_2140_agt_2008_8_1647
Sato, Masatoshi. A class function on the mapping class group of an orientable surface and the Meyer cocycle. Algebraic and Geometric Topology, Tome 8 (2008) no. 3, pp. 1647-1665. doi: 10.2140/agt.2008.8.1647
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