arXiv research

Odd covers have one Anosov flow, even covers have two.

We study isometric cohomogeneity one actions on the (n+1)-dimensional Minkowski space up to orbit-equivalence. We give examples of isometric cohomogeneity one actions on the Minkowski space whose orbit spaces are non-Hausdorff. We show that there exist isometric cohomogeneity one actions on the Minkowski space which ar…

New framework mated Kleinian groups with complex polynomials, revealing unique group properties.

Smooth orbit equivalence proves metric equivalence for geodesic flows.

The paper proves rigidity results for Anosov flows and their orbit equivalences.

Classifies foliations on specific symmetric spaces.

New insights into pseudo-Anosov flows with special periodic orbits.

We show that a self orbit equivalence of a transitive Anosov flow on a $3$-manifold which is homotopic to identity has to either preserve every orbit or the Anosov flow is $\mathbb{R}$-covered and the orbit equivalence has to be of a specific type. This result shows that one can remove a relatively unnatural assumption…

Classifies actions on Minkowski space up to orbit equivalence.

Classifies pseudo-Anosov flows on 3-manifolds up to orbit equivalence.

We present a simple approach to questions of topological orbit equivalence for actions of countable groups on topological and smooth manifolds. For example, for any action of a countable group $Γ$ on a topological manifold where the fixed sets for any element are contained in codimension two submanifolds, every orbit e…

We establish orbit equivalence rigidity for any ergodic, essentially free and measure-preserving action on a standard Borel space with a finite positive measure of the mapping class group for a compact orientable surface with higher complexity. We prove similar rigidity results for a finite direct product of mapping cl…

Classifies actions on complex space forms with Lagrangian orbits.

Classifies polar actions on 3D homogeneous spaces.

Classifies polar foliations on symmetric spaces.

Generalizes Anosov flows to partially hyperbolic diffeomorphisms.

Algorithm decides if pseudo-Anosov flows have perfect fits.

We classify polar actions on complex hyperbolic spaces up to orbit equivalence.

The paper studies cohomogeneity one actions on pseudo-Euclidean space and identifies unique orbit structures.

Constructs graph manifolds with many Anosov flows.

New structural result classifies actions on symmetric spaces.

Study proves hyperfiniteness of mapping class group actions on surface graphs.

We classify, up to orbit equivalence, the cohomogeneity one actions on the noncompact duals of the symmetric spaces G_2, SU_3 and the real oriented two-plane Grassmannians.

Study of flows on 7D manifolds with holomorphic properties.

We classify the polar actions on the complex hyperbolic plane up to orbit equivalence. Apart from the trivial and transitive polar actions, there are five polar actions of cohomogeneity one and four polar actions of cohomogeneity two.

Complete classification of symmetric spaces actions.

We study hyperpolar actions on reducible symmetric spaces of the compact type. Our main result is that an indecomposable hyperpolar action on a symmetric space of the compact type is orbit equivalent to a Hermann action or of cohomogeneity one.

Horizontal surgery on pseudo-Anosov flows yields almost equivalent flows.

Let M be a Margulis spacetime whose associated complete hyperbolic surface S has compact convex core. Generalizing the correspondence between closed geodesics on M and closed geodesics on S, we establish an orbit equivalence between recurrent spacelike geodesics on M and recurrent geodesics on S. In contrast, no timeli…

We prove the following to results: (1) A subgroup G of the isometry group of a Riemannian manifold M acts properly on M if and only if G is closed in the isometry group of M. (2) The orbits of an isometric action are closed if and only if the action is orbit equivalent to a proper isometric action.

New surgery method preserves Anosov flow properties using bi-contact geometry.

Study of flows on complex manifolds with holomorphic properties.

In this paper we classify, up to orbit equivalence, cohomogeneity one actions of connected closed Lie subgroups of $U(1,n)$ on the $(2n+1)$-dimensional anti de Sitter spacetime $AdS^{2n+1}$. We also give some new examples of nonproper cohomogeneity one actions on $AdS^{n+1}$ and determine parabolic Lie subgroups of $SO…

The paper proves actions of lattices in higher rank groups have cost one.

The aim of this paper is to classify the cohomogeneity one conformal actions on the three-dimensional essential Riemannian spaces, up to orbit equivalence. Among other results, the representations of all connected Lie groups acting with cohomogeneity one or zero within the full conformal group of a given three-dimensio…

We study polar actions with horizontal sections on the total space of certain principal bundles $G/K\to G/H$ with base a symmetric space of compact type. We classify such actions up to orbit equivalence in many cases. In particular, we exhibit examples of hyperpolar actions with cohomogeneity greater than one on locall…

Constructs Anosov flows in hyperbolic 3-manifolds, disproving a conjecture.

The paper studies Liouville structures for taut foliations and Anosov flows, proving their topological invariance.

Groups acting on CAT(0) cube complexes have hyperfinite boundary actions.

We classify, up to orbit equivalence, all cohomogeneity one actions on the hyperbolic planes over the complex, quaternionic and Cayley numbers, and on the complex hyperbolic spaces of dimension greater than two. For the quaternionic hyperbolic spaces of dimension greater than two we reduce the classification problem to…

New examples of hypersurfaces found in quaternionic hyperbolic spaces.

In this paper we study obstructions to presentability by products for finitely generated groups. Along the way we develop both the concept of acentral subgroups, and the relations between presentability by products on the one hand, and certain geometric and measure or orbit equivalence invariants of groups on the other…

An isometric action of a Lie group on a Riemannian manifold is of cohomogeneity one if the corresponding orbit space is one-dimensional. In this article we develop a conceptual approach to the classification of cohomogeneity one actions on Riemannian symmetric spaces of noncompact type in terms of orbit equivalence. As…

For the implicit systems of first order ordinary differential equations on the plane there is presented the complete local classification of generic singularities of family of its phase curves up to smooth orbital equivalence. Besides the well known singularities of generic vector fields on the plane and the singularit…

The paper deals with the program of determining the complexity of various homeomorphism relations. The homeomorphism relation on compact Polish spaces is known to be reducible to an orbit equivalence relation of a continuous Polish group action (Kechris-Solecki). It is shown that this result extends to locally compact …

Study automorphism groups of Artin groups, proving rigidity and classification results.

Handlebody groups are rigid under measure equivalence.

Study graph products of groups, classifying them up to measure equivalence and rigidity.