Given a finite group G and a G-space X, we show that a direct sum FG(X) = ⊕ n≥0KGn(X n) ⊗ C admits a natural graded Hopf algebra and λ-ring structure, where Gn denotes the wreath product G ∼ Sn. FG(X) is shown to be isomorphic to a certain supersymmetric product in terms of KG(X) ⊗ C as a graded algebra. We further prove that FG(X) is isomorphic to the Fock space of an infinite dimensional Heis...

We consider a first order linear partial differential operator of principal type on a closed connected orientable two-dimensional manifold sending sections of one complex line bundle to sections of another. We prove that the assumption of global hypoellipticity of the operator implies a relation between the degrees of the line bundles and the Euler characteristic of the manifold.

For a bounded domain Ω ⊂ Rm,m ≥ 2, of class C0, the properties are studied of fields of ‘good directions’, that is the directions with respect to which ∂Ω can be locally represented as the graph of a continuous function. For any such domain there is a canonical smooth field of good directions defined in a suitable neighbourhood of ∂Ω, in terms of which a corresponding flow can be defined. Using...

We find a quartic example of a smooth embedded negatively curved surface in R homeomorphic to a doubly punctured torus. This constitutes an explicit solution to Hadamard’s problem on constructing complete surfaces with negative curvature and Euler characteristic in R. Further we show that our solution has the optimal degree of algebraic complexity via a topological classification for smooth cub...

We compute the Euler-Poincaré characteristic of quotients of the Bruhat-Tits building of PGL(n) under the action of arithmetic groups arising from central division algebras over rational function fields of positive characteristic. We use this result to determine the structure of the quotient simplicial complex in certain cases.

The aim of this note is to study the behavior of intersection homology Euler characteristic under morphisms of algebraic varieties. The main result is a direct application of the BBDG decomposition theorem. Similar formulae for Hodge-theoretic invariants of algebraic varieties were announced by the first and third authors in [4, 11].

The generating function for Sn-equivariant Euler characteristics of moduli spaces of pointed hyperelliptic curves for any genus g ≥ 2 is calculated. This answer generalizes the known ones for genera 2 and 3 and answers obtained by J. Bergstrom for any genus and n ≤ 7 points.

The Euler characteristic, thought of as a function that assigns a numerical value to every finite simplicial complex, is locally determined in both a combinatorial sense and a geometric sense. In this note we show that not every function that assigns a numerical value to every finite simplicial complex via a linear combination of the numbers of simplices in each dimension is locally determined ...

We show how to calculate the Euler characteristic of an affine Jacobi variety of a spectral curve from its defining equations. 0 Membre du CNRS 1 Laboratoire associé au CNRS.

We consider properly immersed finite topology minimal surfaces Σ in complete finite volume hyperbolic 3-manifolds N , and in M × S, where M is a complete hyperbolic surface of finite area. We prove Σ has finite total curvature equal to 2π times the Euler characteristic χ(Σ) of Σ, and we describe the geometry of the ends of Σ. .