Homology, Homotopy and Applications

Volume 5 (2003)

Number 1

The Bloch invariant as a characteristic class in $B(SL_2(C),T)$

Pages: 325 – 344

DOI: http://dx.doi.org/10.4310/HHA.2003.v5.n1.a14


José Luis Cisneros-Molina (Instituto de Matemáticas, UNAM, Unidad Cuernavaca, Morelos, Mexico)

John D. S. Jones (Mathematics Institute, University of Warwick, Coventry, United Kingdom)


Given an orientable complete hyperbolic 3-manifold of finite volume $M$ we construct a canonical class $\alpha(M)$ in $H_3(B(SL_2(C),T))$ with $B(SL_2(C),T)$ the $SL_2(C)$-orbit space of the classifying space for a certain family of isotropy subgroups. We prove that $\alpha (M)$ coincides with the Bloch invariant $\beta(M)$ of $M$ defined by Neumann and Yang in [13], giving with this a simpler proof that the Bloch invariant is independent of an ideal triangulation of $M$. We also give a new proof of the fact that the Bloch invariant lies in the Bloch group $B(C)$.


hyperbolic 3-manifolds, Classifying space for families of isotropy subgroups, Bloch group, Bloch invariant, acyclic maps

2010 Mathematics Subject Classification

19Dxx, 19Exx, 53-xx, 57M27

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