Formal Poisson Cohomology of Twisted r–Matrix Induced Structures

Quadratic Poisson tensors of the Dufour-Haraki classification read as a sum of an r-matrix induced structure twisted by a (small) compatible exact quadratic tensor. An appropriate bigrading of the space of formal Poisson cochains then leads to a vertically positive double complex. The associated spectral sequence allows to compute the Poisson-Lichnerowicz cohomology of the considered tensors. We depict this modus operandi, apply our technique to concrete examples of twisted Poisson structures, and obtain a complete description of their cohomology. As richness of Poisson cohomology entails computation through the whole spectral sequence, we detail an entire model of this sequence. Finally, the paper provides practical insight into the operating mode of spectral sequences. Key-words: Poisson-Lichnerowicz cohomology, r-matrix induced Poisson tensor, exact quadratic structure, vertically positive double complex, spectral sequence 2000 Mathematics Subject Classification: 17B63, 17B56, 55T05