#### Volume 12, issue 2 (2012)

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Geometric interpretation of simplicial formulas for the Chern–Simons invariant

### Julien Marché

Algebraic & Geometric Topology 12 (2012) 805–827
##### Abstract

We give a direct interpretation of Neumann’s combinatorial formula for the Chern–Simons invariant of a 3–manifold with a representation in $PSL\left(2,ℂ\right)$ whose restriction to the boundary takes values in upper triangular matrices. Our construction does not involve group homology or Bloch group but is based on the construction of an explicit flat connection for each tetrahedron of a simplicial decomposition of the manifold.

##### Keywords
Chern–Simons, triangulation, simplicial formula
##### Mathematical Subject Classification 2010
Primary: 57M27, 58J28