The cohomology of the braid group B_3 and of SL_2(Z) with coefficients   in a geometric representation
  The purpose of this article is to describe the integral cohomology of the braid group B_3 and SL_2(Z) with local coefficients in a classical geometric representation given by symmetric powers of the natural symplectic representation.   These groups have a description in terms of the so called "divided polynomial algebra". The results show a strong relation between torsion part of the computed cohomology and fibrations related to loop spaces of spheres. 
Filippo Callegaro, Fred Cohen, Mario Salvetti
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