In this paper we study some new theories of characteristic homology classes of singular complex algebraic (or compactifiable analytic) spaces.We introduce a motivic Chern class transformation mCy: K 0 (var/X) → G 0 (X) ⊗ Z[y], which generalizes the total λ-class λy(T * X) of the cotangent bundle to singular spaces. Here K 0 (var/X) is the relative Grothendieck group of complex algebraic varieties over X as introduced and studied by Looijenga and Bittner in relation to motivic integration, and G 0 (X) is the Grothendieck group of coherent sheaves of O X -modules. A first construction of mCy is based on resolution of singularities and a suitable "blow-up" relation, following the work of Du Bois, Guillén, Navarro Aznar, Looijenga and Bittner. A second more functorial construction of mCy is based on some results from the theory of algebraic mixed Hodge modules due to M. Saito.We define a natural transformation Ty * : K 0 (var/X) → H * (X) ⊗ Q[y] commuting with proper pushdown, which generalizes the corresponding Hirzebruch characteristic. Ty * is a homology class version of the motivic measure corresponding to a suitable specialization of the well-known Hodge polynomial. This transformation unifies the Chern class transformation of MacPherson and Schwartz (for y = −1), the Todd class 1 2 J.-P. Brasselet, J. Schürmann & S. Yokura transformation in the singular Riemann-Roch theorem of Baum-Fulton-MacPherson (for y = 0) and the L-class transformation of Cappell-Shaneson (for y = 1).We also explain the relation among the "stringy version" of our characteristic classes, the elliptic class of Borisov-Libgober and the stringy Chern classes of Aluffi and De Fernex-Lupercio-Nevins-Uribe.All our results can be extended to varieties over a base field k of characteristic 0.We introduce characteristic homology class transformations mC y and T y * on K 0 (var/X) related by the following commutative diagram:by taking fiberwise the (topological) Euler characteristic with compact support. Note that the homomorphisms e and mC 0 are surjective. Remark 0.1. Note that in the algebraic context the Chern-Schwartz-MacPherson transformation c * of [44] is defined only on spaces X embeddable into a smooth space (e.g. for quasi-projective varieties). But using the technique of "Chow envelopes" as in [31, Sec. 18.3], this transformation can uniquely be extended to all (reduced) separated schemes of finite type over spec(k). 4 J.-P. Brasselet, J. Schürmann & S. YokuraFor X a compact complex algebraic variety, we can also construct the following commutative diagram of natural transformations:4) with L * the homology L-class transformation of Cappell-Shaneson [21] (as reformulated by Yokura [81]). Here Ω(X) is the Abelian group of cobordism classes of self-dual constructible complexes. To make Ω(·) covariant functorial (correcting [81]), we use the definition of a "cobordism" given by Youssin [89] in the more general context of triangulated categories with duality. Note that the homology L-class transformation of Cappell-Shaneson [21] is defined o...

In 1981 W. Fulton and R. MacPherson introduced the notion of bivariant theory (BT), which is a sophisticated unification of covariant theories and contravariant theories. This is for the study of singular spaces. In 2001 M. Levine and F. Morel introduced the notion of algebraic cobordism, which is a universal oriented Borel–Moore functor with products (OBMF) of geometric type, in an attempt to understand better V. Voevodsky's (higher) algebraic cobordism. In this paper we introduce a notion of oriented bivariant theory (OBT), a special case of which is nothing but the oriented Borel–Moore functor with products. The present paper is a first one of the series to try to understand Levine–Morel's algebraic cobordism from a bivariant theoretical viewpoint, and its first step is to introduce OBT as a unification of BT and OBMF.

Abstract. We prove generating series formulae for suitable twisted characteristic classes of symmetric products of a singular complex quasi-projective variety. More concretely, we study homology Hirzebruch classes for motivic coefficients, as well as for complexes of mixed Hodge modules. As a special case, we obtain a generating series formula for the (intersection) homology Hirzebruch classes of symmetric products. In some cases, the latter yields a similar formula for twisted homology L-classes generalizing results of Hirzebruch-Zagier and Moonen. Our methods also apply to the study of Todd classes of (complexes of) coherent sheaves, as well as Chern classes of (complexes of) constructible sheaves, generalizing to arbitrary coefficients results of Moonen and resp. Ohmoto.

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ABSTRACT. A theory of characteristic classes of vector bundles and smooth manifolds plays an important role in the theory of smooth manifolds. An investigation of reasonable notions of characteristic classes of singular spaces started since a systematic study of singular spaces such as singular algebraic varieties. We make a quick survey of characteristic classes of singular varieties, mainly focusing on the functorial aspects of some important ones such as the singular versions of the Chern class, the Todd class and the Thom-Hirzebruch's L-class. Then we explain our recent "motivic" characteristic classes, which in a sense unify these three different theories of characteristic classes. We also discuss bivariant versions of them and characteristic classes of proalgebraic varieties, which are related to the motivic measures/integrations. Finally we explain some recent work on "stringy" versions of these theories, together with some references for "equivariant" counterparts.

The Hirzebruch-Riemann-Roch theorem (HRR) for vector bundles on a non-singular complex variety was generalized by Grothendieck (GRR) and further extended to singular varieties by Baum, Fulton and MacPherson (BFM-RR). The HRR says, symbolically speaking, that χ = T , where χ denotes the Euler-Poincaré characteristic of the bundle and T denotes its Todd characteristic. Hirzebruch generalized these two characteristics to χ y and T y , introducing a parameter y, and he showed that χ y = T y. In this paper we give a "BFM-RR version" of this generalized HRR. 2. Riemann-Roch theorems. In this section we briefly recall the above-mentioned three Riemann-Roch theorems in a historical order. Let X be a non-singular complex projective variety and E a holomorphic vector bundle over X. Let χ(X, E) = ∞ i=0 (−1) i dim C H i (X; Ω(E)) be the Euler-Poincaré characteristic, where Ω(E) is the coherent sheaf of germs of sections of E. J.-P. Serre conjectured and F. Hirzebruch solved that this Euler number can be expressed in terms of Chern classes of E and the tangent bundle T X. Namely, the following theorem is a celebrated theorem, usually called the Hirzebruch-Riemann-Roch theorem: Theorem 1 (HRR).

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The existence of bivariant Chern classes was conjectured by W. Fulton and R. MacPherson and proved by J.-P. Brasselet for cellular morphisms of analytic varieties. However, its uniqueness has been unresolved since then. In this paper we show that restricted to morphisms whose target varieties are possibly singular but (rational) homology manifolds (such as orbifolds), the bivariant Chern classes (with rational coefficients) are uniquely determined. And also we discuss some related things and problems. In the final sections we construct a unique bivariant Chern class γ : F → H satisfying a suitable normalization condition. In fact, it will be a special case of a general construction of unique Grothendieck transformations, which in a sense gives a positive answer to the uniqueness questions concerning Grothendieck transformations posed by Fulton and MacPherson.