A class function on the mapping class group of an orientable surface and the Meyer cocycle
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چکیده
Meyer [9] defined a cocycle g 2Z.MgIZ/ (g 0) called the Meyer cocycle which represents four times generator of the second cohomology class when g 3. Let D1 , D2 , and D3 be mutually disjoint disks in S , and Int Di the interior of Di for i D 1; 2; 3. We denote by P WDS q iD1 Int Di the pair of pants, and ̨; ˇ; 2 1.P / be the homotopy classes as shown in Figure 1. We consider a †g;r –bundle E '; g;r on the pair of pants P which has monodromies ' , , . '/ 1 2Mg;r along ̨ , ˇ ,
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تاریخ انتشار 2008