Classifies compact spaces by shape, finite spaces by weak homotopy.
problem Classifying compact Hausdorff spaces and finite topological spaces.
method Constructs a category that classifies spaces by shape and weak homotopy.
result Classifies compact spaces by shape, finite spaces by weak homotopy.
New groups without finite classifying spaces found in Kodaira fibrations.
problem Finding groups without finite classifying spaces.
method Constructing Kähler groups as fundamental groups of Kodaira fibrations.
result Found Kähler groups that are not commensurable to surface groups and do not have finite classifying spaces.
The study classifies flows of finite curvature in 3D space.
problem Classifying flows of finite curvature in 3D space.
method Partial classification of eternal mean convex flows.
result Topologically nonplanar flows must exit a catenoid.
Classifies finite orbits of mapping class group actions on surface group representations.
problem Finite orbits of mapping class group actions on surface group representations.
method Classification based on surface genus and representation properties.
result Finite orbits correspond to homomorphisms with finite image for genus at least two, and to finite or special dihedral representations for genus one.
Study shows k-NN classifier is not universally consistent on (0,1) but consistent on discrete and specific measure spaces.
problem Consistency of k-NN classifier under Wasserstein distance on measure spaces. method Analysis of k-NN classifier properties under Wasserstein distance, use of σ-finite metric dimension, geodesic structures of Wasserstein spaces. result Consistency of k-NN classifier on specific measure spaces (discrete, Gaussian, wavelet series) but not on (0,1). We construct Kähler groups with arbitrary finiteness properties by mapping products of closed Riemann surfaces holomorphically onto an elliptic curve: for each r≥3, we obtain large classes of Kähler groups that have classifying spaces with finite (r−1)-skeleton but do not have classifying spaces with finitely m…
Classifies toric dually flat manifolds into complex space forms.
problem Classifying 1D toric dually flat manifolds.
method Using complex space forms and exponential families.
result Toric dually flat manifolds are complex space forms.
Outer space for RAAGs is a contractible finite-dimensional space for automorphisms.
problem Constructing a finite-dimensional space for outer automorphisms of RAAGs.
method Constructing a finite-dimensional space OΓ blending features of symmetric spaces and Outer space for free groups. result The space OΓ is contractible, making the quotient a rational classifying space for extOut(AΓ). We prove a long-standing conjecture about complex reflection arrangements.
problem The K(π,1) conjecture for affine Artin groups. method Recent advancements in dual Coxeter and Artin groups theory, new constructions, and poset shellability.
result The complexified complement of an affine reflection arrangement is a classifying space.
Classifies 3D spaces using specific invariants.
problem Classifying 3D simply connected Mori fibre spaces.
method Uses finitely many numerical invariants.
result Finds finitely many invariants to classify diffeomorphism types.
We define for a topological group G and a family of subgroups F two versions for the classifying space for the family F, the G-CW-version E_F(G) and the numerable G-space version J_F(G). They agree if G is discrete, or if G is a Lie group and each element in F compact, or if F is the family of compact subgroups. We dis…
Quandles can be regarded as generalizations of symmetric spaces. In the study of symmetric spaces, the notion of flatness plays an important role. In this paper, we define the notion of flat quandles, by referring to the theory of Riemannian symmetric spaces, and classify flat connected finite quandles.
New Kähler groups found from surface groups.
problem Understanding Kähler subgroups of direct products of surface groups.
method Construction of infinite classes of Kähler groups.
result New classes of irreducible, coabelian Kähler subgroups of direct products of surface groups.
New classifying spaces constructed from Ore categories with Garside families.
problem Constructing classifying spaces for fundamental groups.
method Using Ore categories with Garside families, introducing Zappa–Szép product.
result New categories and groups constructed, including Braided T of type F∞. The main theorem shows that if M is an irreducible compact connected orientable 3-manifold with non-empty boundary, then the classifying space BDiff(M rel dM) of the space of diffeomorphisms of M which restrict to the identity map on boundary(M) has the homotopy type of a finite aspherical CW-complex. This answers, for…
Finite index subgroups of relatively hyperbolic groups have equal index.
problem Finite index subgroups of relatively hyperbolic groups have equal index.
method Demonstrating that the number of simplices in a simplicial classifying space grows linearly with index.
result Finite index subgroups of relatively hyperbolic groups have equal index.
Affine Artin groups have a finite classifying space.
problem Proving the K(π,1) conjecture for affine Artin groups. method Dual Garside structures, Euclidean isometries, and shellability of noncrossing partitions.
result Affine Artin groups have a finite classifying space.
Bar-Natan used Chinese characters to show that finite type invariants classify string links up to homotopy. In this paper, I construct the correct spaces of chord diagrams and Chinese characters for links up to homotopy. I use these spaces to show that the only rational finite type invariants of link homotopy are the p…
In this paper we study the homogeneous Kaehler manifolds (h.K.m.) which can be Kaehler immersed into finite or infinite dimensional complex space forms. On one hand we completely classify the h.K.m. which can be Kaehler immersed into a finite or infinite dimensional complex Euclidean or hyperbolic space. Moreover, we e…
Study automorphism groups of right-angled Artin groups, proving they are type VF.
problem Characterize the outer automorphism groups of right-angled Artin groups.
method Construct subnormal series, study restriction homomorphisms, refine previous work.
result Prove Out(AΓ) is type VF with finite index subgroup having finite classifying space. New structural result classifies actions on symmetric spaces.
problem Classify cohomogeneity one actions on symmetric spaces.
method Developed new structural result and applied to specific cases.
result Classified cohomogeneity one actions on SL(n,R)/SO(n), n>1.
Decomposition complexity for metric spaces was recently introduced by Guentner, Tessera, and Yu as a natural generalization of asymptotic dimension. We prove a vanishing result for the continuously controlled algebraic K-theory of bounded geometry metric spaces with finite decomposition complexity. This leads to a proo…
Classifies Lie group representations linked to quaternion-Kähler symmetric spaces.
problem Classifying representations of Lie groups with specific orbit spaces.
method Analyzing representations of Sp(1)k-extensions and quaternion-Kähler symmetric spaces. result Representations are derived from isotropy representations of quaternion-Kähler symmetric spaces.
Defines an equivariant cobordism category for finite groups.
problem Understanding geometric structures with group actions.
method Introduces a new category for (d−1)-dimensional closed smooth G-manifolds and their cobordisms. result Identifies the homotopy type of the classifying space of the equivariant cobordism category as fixed points of an infinite loop space.
Let S be a non-exceptional oriented surface of finite type. We classify all Radon measures on the space of measured geodesic laminations for S which are invariant under the mapping class group.
The paper classifies equivariant test configurations for spherical varieties.
problem Classifying equivariant test configurations for spherical varieties.
method Combinatorial data classification of equivariant normal R-test configurations.
result Finiteness theorem of central fibers of G-equivariant special R-test configurations.
Finite type for 3-manifolds with boundary.
problem Finite type for 3-manifolds with boundary.
method Contractible space of reducing spheres, homotopy type of finite CW complex.
result B Diff(M rel boundary) has the homotopy type of a finite CW complex.
The paper extends CMC surface theory to product spaces, proving height estimates and classifying surfaces.
problem Extending CMC surface theory to product spaces with specific curvature conditions.
method Analyzing graphs and using angle function to derive curvature estimates and classify surfaces.
result Classification of all simply connected, properly embedded surfaces with finite topology.
Classifies vector field algebras in complex space.
problem Classifying vector field algebras in complex space.
method Classical results and proofs for vector fields in 2 and 3 variables, extended to arbitrary N.
result Lie's classification for vector fields in CN. The paper classifies energy-minimizing sets in specific domains.
problem Classifying volume-constraint local energy-minimizing sets.
method Proved a Poincaré-type inequality for stable sets.
result Relative boundary of energy-minimizing sets is smooth.
Finite type and finitely generated homotopy groups for manifold automorphisms.
problem Finite type and homotopy group properties of manifold automorphism spaces.
method Analyzing the classifying space of diffeomorphism groups and using simple homotopy theory.
result The classifying space of diffeomorphism groups has finitely generated homotopy groups.
We associate a contractible ``outer space'' to any free product of groups G=G_1*...*G_q. It equals Culler-Vogtmann space when G is free, McCullough-Miller space when no G_i is Z. Our proof of contractibility (given when G is not free) is based on Skora's idea of deforming morphisms between trees. Using the action of Ou…
We classify orthogonal actions of finite groups on Euclidean vector spaces for which the corresponding quotient space is a topological, homological or Lipschitz manifold, possibly with boundary. In particular, our results answer the question of when the underlying space of an orbifold is a manifold.
Classifies GL(2,R)-invariant subvarieties in complex geometry.
problem Classifying GL(2,R)-invariant subvarieties.
method Classification of natural subvarieties including double covers and Teichmüller space.
result Classification of high rank invariant subvarieties and new examples.
We prove that every finite connected simplicial complex has the homology of the classifying space for some CAT(0) cubical duality group. More specifically, for any finite simplicial complex X, we construct a locally CAT(0) cubical complex TX and an acyclic map tX:TX→X such tha…
Torelli space (in genus g) is the moduli space of compact Riemann surfaces of genus g together with a symplectic basis of their first homology group. It is the quotient of the genus g Teichmuller space by the Torelli group T_g and is a model of the classifying space of T_g. It is known that almost all T_g are not finit…
Researchers classify and decompose valuations on convex functions.
problem Classifying valuations on convex functions.
method Geometric decomposition of valuations, using properties of special subspaces and Monge-Ampère-type operators.
result Valuations decompose into subspaces defined by vanishing properties.
Study confirms non-injective monodromy for even genus 4 translation surfaces.
problem Characterizing monodromy of translation surfaces in even genus 4.
method Analysis of orbifold classifying spaces and finite-type Artin groups.
result Monodromy of Heven(6) contains a non-abelian free group of rank 2. We extend the notion of Novikov-Shubin invariant for free G-CW-complexes of finite type to spaces with arbitrary G-actions and prove some statements about their positivity. In particular we apply this to classifying spaces of discrete groups.
Classifies symplectic Lie algebras and their associated manifolds.
problem Classifying finite-dimensional Lie algebras of symplectic vector fields.
method Using E. Cartan's prolongation theory and symplectic geometry, classify Lie algebras and their associated manifolds.
result Classifies all graded transitive finite-dimensional subalgebras of symplectic vector fields.
This paper categorifies Quinn's TQFTs and computes them for specific omega-groupoids.
problem Constructing and computing finite total homotopy TQFTs.
method Direct homotopy theoretical construction, categorification of Quinn's TQFTs, explicit computation for omega-groupoids.
result Categorification and explicit computation of Quinn's TQFTs for omega-groupoids.
In this paper we present a new Bayesian network model for classification that combines the naive-Bayes (NB) classifier and the finite-mixture (FM) classifier. The resulting classifier aims at relaxing the strong assumptions on which the two component models are based, in an attempt to improve on their classification pe…
Associated to each finite dimensional linear representation of a group G, there is a vector bundle over the classifying space BG. This construction was studied extensively for compact groups by Atiyah and Segal. We introduce a homotopy theoretical framework for studying the Atiyah-Segal construction in the context of i…
We describe a class of real Banach manifolds, which classify K−1. These manifolds are Grassmannians of (hermitian) lagrangian subspaces in a complex Hilbert space. Certain finite codimensional real subvarieties described by incidence relations define geometric representatives for the generators of the cohomology r…
We prove a homological version of a conjecture about the homotopy type of diffeomorphism spaces of reducible 3-manifolds.
problem Proving a conjecture about the homotopy type of diffeomorphism spaces of reducible 3-manifolds.
method Homological approach to show finitely many nonzero homology groups, each finitely generated.
result BDiff(M, rel ∂) has finitely many nonzero homology groups, each finitely generated, for connected sums of irreducible 3-manifolds with nontrivial and non-spherical boundaries.
Models for self-equivalences and diffeomorphisms of manifolds.
problem Classifying spaces of self-equivalences and diffeomorphisms of manifolds.
method Construct rational models using equivariant algebraic methods.
result Formula for rational cohomology of classifying spaces.
Convolutional neural networks handle rotated image symmetries without dimensionality issues.
problem Binary image classification with rotational symmetry.
method Least squares plug-in classifiers based on convolutional neural networks under rotationally symmetric assumptions.
result Convolutional neural networks can circumvent the curse of dimensionality in binary image classification with rotational symmetry.
We classify Kähler-Einstein manifolds which admit a Kähler immersion into a finite dimensional complex projective space endowed with the Fubini-Study metric, whose codimention is not greater than 3 and whose metric is rotation invariant.