In this Note we investigate about some relations between Poincaré dual and other topological objects, such as intersection index, topological degree, and Maslov index of Lagrangian submanifolds. A simple proof of the Poincaré-Hopf theorem is recalled. The Lagrangian submanifolds are the geometrical, multi-valued, solutions of physical problems of evolution governed by Hamilton-Jacobi equations: the computation of the algebraic number of the branches is showed to be performed by using Poincaré dual....

In this survey, we consider several questions pertaining to homeomorphisms, including criteria for their existence in certain circumstances, and obstructions to their existence.

Nous considérons l’action de la monodromie sur l’homologie de la fibre de Milnor d’une singularité complexe. Cette action est plus compliquée que prévu : en effet nous montrons que, sur $\mathbf{Z}$, elle n’est, en général, pas somme directe de modules cycliques. Nous donnons également des exemples prouvant que la monodromie rationnelle ne détermine pas la monodromie entière et que la monodromie entière ne détermine pas la topologie.

Using fiberings, we determine the cup-length and the Lyusternik-Shnirel’man category for some infinite families of real flag manifolds $O(n₁+...+n_q)/O\left(n₁\right)\times ...\times O\left(n_q\right)$, q ≥ 3. We also give, or describe ways to obtain, interesting estimates for the cup-length of any $O(n₁+...+n_q)/O\left(n₁\right)\times ...\times O\left(n_q\right)$, q ≥ 3. To present another approach (combining well with the “method of fiberings”), we generalize to the real flag manifolds Stong’s approach used for calculations in the ℤ₂-cohomology algebra of the Grassmann manifolds.

This paper is a continuation of [19], [21], [22]. We study flat connections with isolated singularities in some transitive Lie algebroids for which either $ℝ$ or $\mathrm{s}l(2,ℝ)$ or $so\left(3\right)$ are isotropy Lie algebras. Under the assumption that the dimension of the isotropy Lie algebra is equal to $n+1$, where $n$ is the dimension of the base manifold, we assign to any such isolated singularity a real number called an index. For $ℝ$-Lie algebroids, this index cannot be an integer. We prove the index theorem (the Euler-Poincaré-Hopf...

Let M be a closed orientable manifold of dimension dand ${𝒞}^{*}\left(M\right)$ be the usual cochain algebra on M with coefficients in a fieldk. The Hochschild cohomology of M, $H{H}^{*}({𝒞}^{*}\left(M\right);{𝒞}^{*}\left(M\right))$ is a graded commutative and associative algebra. The augmentation map $\epsilon :{𝒞}^{*}\left(M\right)\to 𝑘$ induces a morphism of algebras $I:H{H}^{*}({𝒞}^{*}\left(M\right);{𝒞}^{*}\left(M\right))\to H{H}^{*}({𝒞}^{*}\left(M\right);𝑘)$. In this paper we produce a chain model for the morphism I. We show that the kernel of I is a nilpotent ideal and that the image of I is contained in the center of $H{H}^{*}({𝒞}^{*}\left(M\right);𝑘)$, which is in general quite small. The algebra $H{H}^{*}({𝒞}^{*}\left(M\right);{𝒞}^{*}\left(M\right))$ is expected to be isomorphic...