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A quasi-automatic semigroup is defined by a finite set of generators, a rational (regular) set of representatives, such that if a is a generator or neutral, then the graph of right multiplication by a on the set of representatives is a…

Group Theory · Mathematics 2019-06-12 Benjamin Blanchette , Christian Choffrut , Christophe Reutenauer

We study conditions under which quasi-conformal homeomorphisms are quasi-isometries. We show that if two nilpotent geodesic Lie groups are quasi-conformally homeomorphic, then they are quasi-isometrically equivalent. We also give more…

We study the large scale geometry of mapping class groups MCG(S), using hyperbolicity properties of curve complexes. We show that any self quasi-isometry of MCG(S) (outside a few sporadic cases) is a bounded distance away from a…

Geometric Topology · Mathematics 2010-04-12 Jason Behrstock , Bruce Kleiner , Yair Minsky , Lee Mosher

We start an analysis of geometric properties of a structure relative to a reduct. In particular, we look at definability of groups and fields in this context. In the relatively one-based case, every definable group is isogenous to a…

Logic · Mathematics 2013-05-22 Thomas Blossier , Amador Martin Pizarro , Frank Olaf Wagner

In this paper we study the minimal and maximal $L^{2}$-cohomology of oriented, possibly not complete, Riemannian manifolds. Our focus will be on both the reduced and the unreduced $L^{2}$-cohomology groups. In particular we will prove that…

Differential Geometry · Mathematics 2022-12-21 Stefano Spessato

Quasi-elliptic cohomology is a variant of elliptic cohomology theories. It is the orbifold K-theory of a space of constant loops. For global quotient orbifolds, it can be expressed in terms of equivariant K-theories. Thus, the constructions…

Algebraic Topology · Mathematics 2018-08-27 Zhen Huan

In this article, part of the author's thesis, we propose a definition for measured quantum groupoid. The aim is the construction of objects with duality including both quantum groups and groupoids. We base ourselves on J. Kustermans and S.…

Operator Algebras · Mathematics 2007-05-23 Franck Lesieur

Recent research in coarse geometry revealed similarities between certain concepts of analysis, large scale geometry, and topology. Property A of G.Yu is the coarse analog of amenability for groups and its generalization (exact spaces) was…

Metric Geometry · Mathematics 2014-01-07 M. Cencelj , J. Dydak , A. Vavpetič

We show that the sum over geometries in the Lorentzian 4-D state sum model for quantum GR in [1] includes terms which correspond to geometries on manifolds with conical singularities. Natural approximations suggest that they can be…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Louis Crane

We explore a definition of uniformity on noncompact manifolds that does not require a Riemannian metric, but is equivalent to bounded gemetry. These are unfinished research notes (and will likely never be published), but since they were…

Differential Geometry · Mathematics 2024-07-25 Jaap Eldering

We initiate a quantitative study of measure equivalence (and orbit equivalence) between finitely generated groups, which extends the classical setting of $\mathrm L^p$ measure equivalence. In this paper, our main focus will be on amenable…

Group Theory · Mathematics 2022-04-18 Thiebout Delabie , Juhani Koivisto , François Le Maître , Romain Tessera

We study the geometry of nonrelatively hyperbolic groups. Generalizing a result of Schwartz, any quasi-isometric image of a non-relatively hyperbolic space in a relatively hyperbolic space is contained in a bounded neighborhood of a single…

Geometric Topology · Mathematics 2010-04-13 Jason Behrstock , Cornelia Drutu , Lee Mosher

We prove quantitative stability of isometries on the first Heisenberg group with sub-Riemannian geometry: every $ (1+ \varepsilon)$-quasi-isometry of the John domain of the Heisenberg group $ \mathbb {H} $ is close to some isometry with…

Functional Analysis · Mathematics 2022-05-06 Daria Isangulova

An irreducible norm closed semigroup of complex matrices is simultaneously similar to a semigroup of partial isometries if and only if (a) the norms of all nonzero members of it are uniformly bounded above and below, and (b) its idempotents…

Functional Analysis · Mathematics 2013-06-12 Alexey I. Popov

The present paper is devoted to investigation of the isometry group of the Gromov-Hausdorff space, i.e., the metric space of compact metric spaces considered up to an isometry and endowed with the Gromov-Hausdorff metric. The main goal is…

Metric Geometry · Mathematics 2018-06-11 Alexander Ivanov , Alexey Tuzhilin

In solid state systems, group representation theory is powerful in characterizing the behavior of quasiparticles, notably the energy degeneracy. While conventional group theory is effective in answering yes-or-no questions related to…

Materials Science · Physics 2024-07-12 Jiayu Li , Ao Zhang , Yuntian Liu , Qihang Liu

This paper introduces hierarchical quasi-clustering methods, a generalization of hierarchical clustering for asymmetric networks where the output structure preserves the asymmetry of the input data. We show that this output structure is…

Machine Learning · Computer Science 2014-04-21 Gunnar Carlsson , Facundo Mémoli , Alejandro Ribeiro , Santiago Segarra

A semi-projective representation is a homomorphism of a finite group into the group of semi-projective transformations of a finite dimensional vector space over a field. Schur's concept of a representation group for projective…

Group Theory · Mathematics 2023-05-05 Massimiliano Alessandro , Christian Gleissner , Julia Kotonski

We characterise the (closeness classes of) quasi-isometric embeddings as the regular monomorphisms in the coarsely Lipschitz category, formalising the notion that they are isomorphisms onto their image. Furthermore, we prove that the…

Metric Geometry · Mathematics 2024-11-14 Robert Tang

This paper introduces almost partitionable sets to generalize the known concept of partitionable sets. These notions provide a unified frame to construct $\mathbb{Z}$-cyclic patterned starter whist tournaments and cyclic balanced sampling…

Combinatorics · Mathematics 2023-11-27 Yanxun Chang , Simone Costa , Tao Feng , Xiaomiao Wang