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Let $M$ be a complex manifold and $S\subset M$ a (possibly singular) subvariety of $M$. Let $f\colon M\to M$ be a holomorphic map such that $f$ restricted to $S$ is the identity. We show that one can associate to $f$ a holomorphic section…

Dynamical Systems · Mathematics 2007-05-23 Marco Abate , Filippo Bracci , Francesca Tovena

We extend Exel's ample tight groupoid construction to non-ample groupoids, even in the general locally Hausdorff case.

General Topology · Mathematics 2020-09-18 Tristan Bice , Charles Starling

In this paper, we study how global index formulas arise in the theory of one-dimensional holomorphic foliation from the microlocal point of view. We give short proofs and generalizations to a few exisiting index formulas concerning…

Algebraic Geometry · Mathematics 2026-02-16 Xia Liao , Xiping Zhang

We present an extension of several results on pairs and varieties to foliated surface pairs. We prove the boundedness of local complements, the local index theorem, and the uniform boundedness of minimal log discrepancies (mlds), as well as…

Algebraic Geometry · Mathematics 2024-06-07 Jihao Liu , Fanjun Meng , Lingyao Xie

Given a singular foliation, we attach an "essential isotropy" group to each of its leaves, and show that its discreteness is the integrability obstruction of a natural Lie algebroid over the leaf. We show that a condition ensuring…

Differential Geometry · Mathematics 2013-11-18 Iakovos Androulidakis , Marco Zambon

We formulate and prove an analog of the Hopf Index Theorem for Riemannian foliations. We compute the basic Euler characteristic of a closed Riemannian manifold as a sum of indices of a non-degenerate basic vector field at critical leaf…

Differential Geometry · Mathematics 2021-01-28 Victor Belfi , Efton Park , Ken Richardson

We consider the equivariant Kasparov category associated to an \'etale groupoid, and by leveraging its triangulated structure we study its localization at the "weakly contractible" objects, extending previous work by R. Meyer and R. Nest.…

K-Theory and Homology · Mathematics 2024-12-23 Christian Bönicke , Valerio Proietti

We offer streamlined proofs of fundamental theorems regarding the index theory for partial self-maps of an infinite set that are bijective between cofinite subsets.

Combinatorics · Mathematics 2015-10-09 P. L. Robinson

We prove a Morse index theorem for action functionals on paths that are allowed to reflect at a hypersurface (either in the interior or at the boundary of a manifold). Both fixed and periodic boundary conditions are treated.

Differential Geometry · Mathematics 2024-06-26 Jared Wunsch , Mengxuan Yang , Yuzhou Zou

Let $\Gamma$ be a discrete finitely generated group. Let $\hat{M}\to T$ be a $\Gamma$-equivariant fibration, with fibers diffeomorphic to a fixed even dimensional manifold with boundary $Z$. We assume that $\Gamma\to \hat{M}\to…

Differential Geometry · Mathematics 2007-05-23 Eric Leichtnam , Paolo Piazza

We prove that if F is a foliation of a compact manifold M with all leaves compact submanifolds, and the transverse saturated category of F is finite, then the leaf space M/F is compact Hausdorff. The proof is surprisingly delicate, and is…

Dynamical Systems · Mathematics 2016-12-12 Steven Hurder , Pawel G. Walczak

We prove that the topological complexity of a finite index subgroup of a hyperbolic group is linear in its index. This follows from a more general result relating the size of the quotient of a free cocompact action of hyperbolic group on a…

Group Theory · Mathematics 2024-10-15 Nir Lazarovich

Using recently introduced Debord-Skandalis Blup's groupoids we study index theory for a compact foliated manifold with boundary inducing a foliation in its boundary. For this we consider first a blup groupoid whose Lie algebroid has…

K-Theory and Homology · Mathematics 2021-04-15 Ibrahim Akrour , Paulo Carrillo Rouse

We introduce a class of locally compact Hausdorff groupoids and show how to associate C*-algebras to them in a way which generalizes the reduced C*-algebra of an 'etale groupoid. Focusing on criteria for simplicity and existence of Cartan…

Operator Algebras · Mathematics 2009-08-29 Klaus Thomsen

We consider all connected and simply connected 7-dimensional Lie groups whose Lie algebras have nilradical $\g_{5,2} = \s \{X_1, X_2, X_3, X_4, X_5 \colon [X_1, X_2] = X_4, [X_1, X_3] = X_5\}$ of Dixmier. First, we give a geometric…

Differential Geometry · Mathematics 2022-09-12 Tuyen T. M. Nguyen , Vu A. Le , Tuan A. Nguyen

We generalise the even local index formula of Connes and Moscovici to the case of spectral triples for a *-subalgebra \A of a general semifinite von Neumann algebra. The proof is a variant of that for the odd case which appears in Part I.…

Operator Algebras · Mathematics 2007-05-23 Alan L. Carey , John Phillips , Adam Rennie , Fyodor A. Sukochev

Every singular foliation has an associated topological groupoid, called holonomy groupoid (see arXiv:math/0612370). In this note we exhibit some functorial properties of this assignment: if a foliated manifold $(M,\mathcal{F}_M)$ is the…

Differential Geometry · Mathematics 2020-03-24 Alfonso Garmendia , Marco Zambon

We prove the Cone Theorem for algebraically integrable foliations. As a consequence, we show that termination of flips implies the b-nefness of the moduli part of a log canonical pair with respect to a contraction, generalising the case of…

Algebraic Geometry · Mathematics 2022-03-03 Florin Ambro , Paolo Cascini , Vyacheslav Shokurov , Calum Spicer

We present Hausdorff versions for Lie Integration Theorems 1 and 2 and apply them to study Hausdorff symplectic groupoids arising from Poisson manifolds. To prepare for these results we include a discussion on Lie equivalences and propose…

Differential Geometry · Mathematics 2021-03-17 Matias del Hoyo , Daniel López Garcia

We use Galois group actions on \'etale cohomology to prove results of formality for dg-operads and dg-algebras with torsion coefficients. Our theory applies, among other related constructions, to the dg-operad of singular chains on the…

Algebraic Topology · Mathematics 2025-08-05 Joana Cirici , Geoffroy Horel