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Given an oriented rational homology 3–sphere M, it is known how
to associate to any Spinc–structure σ on M two quadratic
functions over the linking pairing. One quadratic function is derived
from the reduction modulo 1 of the Reidemeister–Turaev torsion of
(M,σ), while the other one can be defined using the intersection
pairing of an appropriate compact oriented 4–manifold with boundary
M. In this paper, using surgery presentations of the manifold M,
we prove that those two quadratic functions coincide. Our proof relies
on the comparison between two distinct combinatorial descriptions of
Spinc–structures on M: Turaev's charges vs Chern vectors.
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