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In previous works, we studied intersection homotopy groups associated to a Goresky and MacPherson perversity and a filtered space. They are defined as the homotopy groups of simplicial sets introduced by P. Gajer. We particularized to…

Algebraic Topology · Mathematics 2026-05-14 Martintxo Saralegi-Aranguren , Daniel Tanré

For an arbitrary complex algebraic variety which is not necessarily pure dimensional, the intersection complex can be defined as the direct sum of the Deligne-Goresky-MacPherson intersection complexes of each irreducible component. We give…

Algebraic Geometry · Mathematics 2020-02-10 Ben Wu

The goal of this paper is to explain how basic properties of perverse sheaves sometimes translate via Riemann-Hilbert correspondences (in both characteristic $0$ and characteristic $p$) to highly non-trivial properties of singularities,…

Algebraic Geometry · Mathematics 2025-03-26 Bhargav Bhatt , Manuel Blickle , Gennady Lyubeznik , Anurag K. Singh , Wenliang Zhang

In two articles by Barthel, Brasselet, Fieseler and Kaup, and, Bressler and Lunts, a combinatorial theory of intersection cohomology and perverse sheaves has been developed on fans. In the first one, one tried to present everything on an…

Algebraic Geometry · Mathematics 2007-05-23 Karl-Heinz Fieseler

We show that intersection homology extends Poincare duality to manifold homotopically stratified spaces (satisfying mild restrictions). This includes showing that, on such spaces, the sheaf of singular intersection chains is…

Geometric Topology · Mathematics 2011-03-31 Greg Friedman

Using Saito's theory of mixed Hodge modules, we study a generalization of Hellus-Schenzel's "cohomologically complete intersection" property. This property is equivalent to perversity of the shifted constant sheaf. We relate the generalized…

Algebraic Geometry · Mathematics 2025-11-06 Qianyu Chen , Bradley Dirks , Sebastian Olano

We present the construction and properties of a self-dual perverse sheaf S_0 whose cohomology fulfills some of the requirements of String theory as outlined by T. Hubsch in hep-th/9612075. The construction of this S_0 utilizes techniques…

Algebraic Topology · Mathematics 2026-03-26 Abdul Rahman

In the case of a compact orientable pseudomanifold, a well-known theorem of M. Goresky and R. MacPherson says that the cap product with a fundamental class factorizes through the intersection homology groups. In this work, we show that this…

Algebraic Topology · Mathematics 2017-05-22 David Chataur , Martintxo Saralegi-Aranguren , Daniel Tanré

Intersection homology is defined for simplicial, singular and PL chains and it is well known that the three versions are isomorphic for a full filtered simplicial complex. In the literature, the isomorphism, between the singular and the…

Algebraic Topology · Mathematics 2025-10-15 David Chataur , Martin Saralegi-Aranguren , Daniel Tanré

The method of intersection spaces associates cell-complexes depending on a perversity to certain types of stratified pseudomanifolds in such a way that Poincar\'e duality holds between the ordinary rational cohomology groups of the…

Algebraic Topology · Mathematics 2011-02-24 Markus Banagl

Let $pi:X\to\Delta$ be a one-parameter degeneration whose central fiber $X_0$ has a single ordinary double point. The nearby- and vanishing-cycle formalism determines a canonical perverse sheaf on $X_0$, obtained from the variation morphism…

Algebraic Geometry · Mathematics 2026-04-07 Abdul Rahman

We propose the notion of perverse coherent sheaves for symplectic singularities and study its properties. In particular, it gives a basis of simple objects in the Grothendieck group of Poisson sheaves. We show that perverse coherent bases…

Representation Theory · Mathematics 2025-10-28 Ilya Dumanski

We consider a hyperplane arrangement in $\mathbb{C}^n$ defined over $\mathbb{R}$, and the associated natural stratification of $\mathbb{C}^n$. The category of perverse sheaves smooth with respect to this stratification was described by…

Representation Theory · Mathematics 2020-11-17 Asilata Bapat

This paper is an introduction to the use of perverse sheaves with positive characteristic coefficients in modular representation theory. In the first part, we survey results relating singularities in finite and affine Schubert varieties and…

Representation Theory · Mathematics 2014-10-07 Daniel Juteau , Carl Mautner , Geordie Williamson

We prove a criterion for determining whether the normalization of a complex analytic space on which the constant sheaf is perverse is a rational homology manifold, using a perverse sheaf known as the multiple-point complex. This perverse…

Algebraic Geometry · Mathematics 2018-08-13 Brian Hepler

In this paper we compare different notions of transversality for possible singular complex algebraic or analytic subsets of an ambient complex manifold and prove a refined intersection formula for their Chern-Schwartz-MacPherson classes. In…

Algebraic Geometry · Mathematics 2016-01-07 Joerg Schuermann

We generalize the first author's construction of intersection spaces to the case of stratified pseudomanifolds of stratification depth 1 with twisted link bundles, assuming that each link possesses an equivariant Moore approximation for a…

Algebraic Topology · Mathematics 2016-07-21 Markus Banagl , Bryce Chriestenson

James McClure recently showed that the domain for the intersection pairing of PL chains on a PL manifold $M$ is a subcomplex of $C_*(M)\otimes C_*(M)$ that is quasi-isomorphic to $C_*(M)\otimes C_*(M)$ and, more generally, that the…

Geometric Topology · Mathematics 2011-03-31 Greg Friedman

Intersection cohomology is a way to enhance classical cohomology, allowing us to use a famous result called Poincar\'e duality on a large class of spaces known as stratified pseudomanifolds. There is a theoretically powerful way to arrive…

Algebraic Topology · Mathematics 2022-12-08 Sebastian Cea

We propose a point of view on resurgence theory based on the study of perverse sheaves on the complex line carrying an algebraic structure with respect to additive convolution. In particular, we lift the concept of alien derivatives…

Algebraic Geometry · Mathematics 2025-12-30 Mikhail Kapranov , Yan Soibelman