We prove that the standard Künneth map in periodic cyclic homology of differential /2graded algebras is compatible with a generalization of the Hodge filtration and explain how this result is related to various Thom-Sebastiani type theorems in singularity theory. DMYTRO SHKLYAROV refer to [8,18] for more details). That the non-commutative Künneth map is compatible with the extensions is an obvious consequence of the explicit formula: roughly, the Künneth map at the level of complexes is regular at u = 0. The non-trivial part of our result is that the map is compatible with the connections.While the compatibility of the classical Künneth map with the mixed Hodge structures on the cohomology of varieties is a good piece of motivation for the subject of the present paper, there are results in geometry of which our theorem is a direct generalization. Namely, our actual aim was to obtain abstract algebraic versions of various Thom-Sebastiani-type results in singularity theory such as, for instance, the Thom-Sebastiani formula for Steenbrink's Hodge filtration on the vanishing cohomology of isolated singularities [15, Sect.8]. The latter calculates the Hodge filtration for the direct sum f ⊕ g of two singularities in terms of the same data for f and g. This result, as well as the original Thom-Sebastiani theorem and some other facts of similar nature, can be deduced from a Künneth property for the Gauss-Manin systems and the Brieskorn lattices associated with the singularities (cf. Lemma 8.7 in loc.cit.) or, equivalently, for the Fourier-Laplace transforms thereof (cf. [14, Sect. 3]). This Künneth property is a special case of our result, as we will explain in Section 3.
Conventions.In Section 2, we work over an arbitrary field k of characteristic 0. In Section 3 the ground field is . Given a /2-graded space V , ΠV will stand for V with the reversed /2-grading, the parity of v ∈ V will be denoted by |v|, and the corresponding element of ΠV will be denoted by Πv. We will follow all the standard conventions of super-linear algebra (such as the Koszul rule of signs, etc.). Finally, only unital dg algebras will be considered.Acknowledgement.