Pure motives, mixed motives and extensions of motives associated to singular surfaces, by J. Wildeshaus

We first recall the construction of the Chow motive modelling intersection cohomology of a proper surface and study its fundamental properties. Using Voevodsky's category of effective geometrical motives, we then study the motive of the exceptional divisor in a non-singular blow-up. If all geometric irreducible components of the divisor are of genus zero, then Voevodsky's formalism allows us to construct certain one-extensions of Chow motives, as canonical sub-quotients of the motive with compact support of the smooth part of the surface. Specializing to Hilbert--Blumenthal surfaces, we recover a motivic interpretation of a recent construction of A. Caspar. This paper extends and replaces no. 778, entitled "Intersection pairing and intersection motive of surfaces".

J. Wildeshaus <wildesh@math.univ-paris13.fr>