An integral-free representation of a line complex with symmetric arrangement of inflection centers

We study complexes ₂ and ₃ with symmetrically situated fourfold inflection centers, two or three of which respectively are infinitely distant on each ray. The class of complexes ₃ turns out to be known. The complex ₂ is new and may involve three arbitrary functions of a single argument. The study of the geometric properties of the complex ₂ culminates in an integral-free representation for it which makes it possible to write out explicitly a solution of the original system of differential equations for the complex.Translated from Ukrainskií Geometricheskií Sbornik, Issue 29, 1986, pp. 125–132.     

The algebraic construction of the Novikov complex of a circle-valued Morse function

The Novikov complex of a circle-valued Morse function is constructed algebraically from the Morse-Smale complex of the restriction of the real-valued Morse function to a fundamental domain of the pullback infinite cyclic cover of M. Received: 23 November 2000 / Revised version: 3 May 2001 / Published online: 28 February 2002     

The number of edges of many faces in a line segment arrangement

We show that the maximum number of edges boundingm faces in an arrangement ofn line segments in the plane isO(m ^2/3 n ^2/3+n(n)+nlogm). This improves a previous upper bound of Edelsbrunner et al. [5] and almost matches the best known lower bound which is (m ^2/3 n ^2/3+n(n)). In addition, we show that the number of edges bounding anym faces in an arrangement ofn line segments with a total oft intersecting pairs isO(m ^2/3 t ^1/3+n(t/n)+nmin{logm,logt/n}), almost matching the lower bound of (m ^2/3 t ^1/3+n(t/n)) demonstrated in this paper.Work on this paper by the first and fourth authors has been partially supported by Office of Naval Research Grant N00014-87-K-0129, by National Science Foundation Grants DCR-83-20085 and CCR-89-01484. Work by the first author has also been supported by an AT&T Bell Laboratories Ph.D. scholarship at New York University and by DIMACS (Center for Discrete Mathematics and Theoretical Computer Science), a National Science Foundation Science and Technology Center (NSF-STC88-09648). Work by the second author has been supported by NSF under Grants CCR-87-14565 and CCR-89-21421. Work by the fourth author has additionally been supported by grants from the U.S.-Israeli Binational Science Foundation, the NCRD (the Israeli National Council for Research and Development) and the Fund for Basic Research in Electronics, Computers and Communication, administered by the Israeli National Academy of Sciences.     

A Morse complex on manifolds with boundary

Given a compact smooth manifold M with non-empty boundary and a Morse function, a pseudo-gradient Morse-Smale vector field adapted to the boundary allows one to build a Morse complex whose homology is isomorphic to the (absolute or relative to the boundary) homology of M with integer coefficients. Our approach simplifies other methods which have been discussed in more specific geometric settings.     

Morse inequalities for the Koszul complex of multi-persistence

In this paper, we define the homological Morse numbers of a filtered cell complex in terms of relative homology of nested filtration pieces, and derive inequalities relating these numbers to the Betti tables of the multi-parameter persistence modules of the considered filtration. Using the Mayer-Vietoris spectral sequence we first obtain strong and weak Morse inequalities involving the above quantities, and then we improve the weak inequalities achieving a sharp lower bound for homological Morse numbers. Furthermore, we prove a sharp upper bound for homological Morse numbers, expressed again in terms of the Betti tables.     

On the equivariant Morse complex of the free loop space of a surface

We prove two theorems about the equivariant topology of the free loop space of a surface. The first deals with the nondegenerate case and says that the ``ordinary' Morse complex can be given an -action in such a way that it carries the -homotopy type of the free loop space. The second says that, in terms of topology, the iterates of an isolated degenerate closed geodesic ``look like' the continuous limit of the iterates of a finite, fixed number of nondegenerate closed geodesics.

     

The geometric complex for algebraic curves with cone-like singularities and admissible Morse functions

In a previous Note the author gave a generalisation of Witten's proof of the Morse inequalities to the model of a singular complex algebraic curve X and a stratified Morse function f. In this Note a geometric interpretation of the complex of eigenforms of the Witten Laplacian corresponding to small eigenvalues is provided in terms of an appropriate subcomplex of the complex of unstable cells of critical points of f. To cite this article: U. Ludwig, C. R. Acad. Sci. Paris, Ser. I 347 (2009).     

A Morse complex for infinite dimensional manifolds—part I

In this paper and in the forthcoming Part II, we introduce a Morse complex for a class of functions f defined on an infinite dimensional Hilbert manifold M, possibly having critical points of infinite Morse index and co-index. The idea is to consider an infinite dimensional subbundle—or more generally an essential subbundle—of the tangent bundle of M, suitably related with the gradient flow of f. This Part I deals with the following questions about the intersection W of the unstable manifold of a critical point x and the stable manifold of another critical point y: finite dimensionality of W, possibility that different components of W have different dimension, orientability of W and coherence in the choice of an orientation, compactness of the closure of W, classification, up to topological conjugacy, of the gradient flow on the closure of W, in the case .     

On the fundamental group of the complement of a complex hyperplane arrangement

We construct two combinatorially equivalent line arrangements in the complex projective plane such that the fundamental groups of their complements are not isomorphic. The proof uses a new invariant of the fundamental group of the complement to a line arrangement of a given combinatorial type with respect to isomorphisms inducing the canonical isomorphism of the first homology groups.     

On the diffeomorphic type of the complement to a line arrangement in a projective plane

We show that the diffeomorphic type of the complement to a line arrangement in a complex projective plane P ² depends only on the graph of line intersections if no line in the arrangement contains more than two points in which at least two lines intersect. This result also holds for some special arrangements which do not satisfy this property. However it is not true in general, see [Rybnikov G., On the fundamental group of the complement of a complex hyperplane arrangement, Funct. Anal. Appl., 2011, 45(2), 137–148].     

Morse index of a cyclic polygon

It is known that cyclic configurations of a planar polygonal linkage are critical points of the signed area function. In the paper we give an explicit formula of the Morse index for the signed area of a cyclic configuration. We show that it depends not only on the combinatorics of a cyclic configuration, but also on its metric properties.     

The Morse Index of Wente Tori

We find various lower and upper bounds for the index of Wente tori that contain a continuous family of planar principal curves. We then prove a result that gives an algorithm for computing the index sharply.     

The Milnor fiber of a generic arrangement

In memoriam Deane Montgomery     

Homotopical dynamics II: Hopf invariants, smoothings and the Morse complex

The ambient framed bordism class of the connecting manifold of two consecutive critical points of a Morse-Smale function is estimated by means of a certain Hopf invariant. Applications include new examples of non-smoothable Poincaré duality spaces as well as an extension of the Morse complex.     

Immersion extension-lift over a Morse function

Let V be a compact connected oriented surface with boundary and f:∂V×[0,1)→R a non-singular function such that f|∂V×{0} is a Morse function. Let ι:∂V×[0,1)→V be a collaring of ∂V and π:R²→R an orthogonal projection. In this paper, we study existence of an orientation preserving immersion F:V→R² such that π°F°ι=f. We also study image homotopy classes of F when we fix f and study relation between two image homotopy classes when f is deformed under a Morse homotopy.     

Bruhat Numbers of a Strong Morse Function

Doklady Mathematics - Let f be a Morse function on a manifold M such that all its critical values are pairwise distinct. Given such a function (together with a certain choice of orientations) and a...