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We study the large scale geometry of the upper triangular subgroup of PSL(2,Z[1/n]), which arises naturally in a geometric context. We prove a quasi-isometry classification theorem and show that these groups are quasi-isometrically rigid…

Geometric Topology · Mathematics 2007-05-23 J. Taback , K. Whyte

Let M,g a compact Riemannian n-dimensional manifold. It is well know that, under certain hypothesis, in the conformal class of g there are scalar-flat metrics that have the boundary of M as a constant mean curvature hypersurface. Also,…

Differential Geometry · Mathematics 2019-12-30 Marco Ghimenti , Anna Maria Micheletti

Let X be a proper hyperbolic geodesic metric space and let G be a closed subgroup of the isometry group Iso(X) of X. We show that if G is not amenable then its second continuous bounded cohomology group with coefficients the regular…

Group Theory · Mathematics 2008-03-16 Ursula Hamenstadt

We provide some language for algebraic study of the mapping class groups for surfaces with non-connected boundary. As applications, we generalize our previous results on Dehn twists to any compact connected oriented surfaces with non-empty…

Geometric Topology · Mathematics 2012-10-23 Nariya Kawazumi , Yusuke Kuno

In this paper we analyze and classify the totally geodesic subspaces of finite volume quaternionic hyperbolic orbifolds and their generalizations, locally symmetric orbifolds arising from irreducible lattices in Lie groups of the form…

Geometric Topology · Mathematics 2015-05-15 Jeffrey S. Meyer

Consider a sequence of closed, orientable surfaces of fixed genus $g$ in a Riemannian manifold $M$ with uniform upper bounds on mean curvature and area. We show that on passing to a subsequence and choosing appropriate parametrisations, the…

Differential Geometry · Mathematics 2008-11-13 Siddartha Gadgil , Harish Seshadri

We give an introduction to the study of algebraic hypersurfaces, focusing on the problem of when two hypersurfaces are isomorphic or close to being isomorphic. Working with hypersurfaces and emphasizing examples makes it possible to discuss…

Algebraic Geometry · Mathematics 2018-10-09 János Kollár

For several instances of metric largeness like enlargeability or having hyperspherical universal covers, we construct non-large vector subspaces in the rational homology of finitely generated groups. The functorial properties of this…

Geometric Topology · Mathematics 2014-02-26 Michael Brunnbauer , Bernhard Hanke

We study groups definable in existentially closed geometric fields with commuting derivations. Our main result is that such a group can be definably embedded in a group interpretable in the underlying geometric field. Compared to earlier…

Logic · Mathematics 2026-04-13 Anand Pillay , Françoise Point , Silvain Rideau-Kikuchi

Suppose a finite group acts on a scheme X and a finite-dimensional Lie algebra g. The corresponding equivariant map algebra is the Lie algebra M of equivariant regular maps from X to g. We classify the irreducible finite-dimensional…

Representation Theory · Mathematics 2012-04-11 Erhard Neher , Alistair Savage , Prasad Senesi

Let $p$ be a prime number and $\mathbb{Z}_p=\mathbb{Z}/p\mathbb{Z}$. We study finite groups with abelian derived subgroup and exponent $p$ in terms of group extension data and their matrix presentations. We show a one-to-one correspondence…

Group Theory · Mathematics 2020-03-31 Zheyan Wan , Yu Ye , Chi Zhang

This is a survey article of geometric properties of noncommutative symmetric spaces of measurable operators $E(\mathcal{M},\tau)$, where $\mathcal{M}$ is a semifinite von Neumann algebra with a faithful, normal, semifinite trace $\tau$, and…

Operator Algebras · Mathematics 2017-04-10 Malgorzata Marta Czerwinska , Anna Kaminska

We describe how the loop group maps corresponding to special submanifolds associated to integrable systems may be thought of as certain Grassmann submanifolds of infinite dimensional homogeneous spaces. In general, the associated families…

Differential Geometry · Mathematics 2008-04-14 David Brander

In this paper we apply a recently proposed algebraic theory of integration to projective group algebras. These structures have received some attention in connection with the compactification of the $M$ theory on noncommutative tori. This…

Mathematical Physics · Physics 2009-10-31 R. Casalbuoni

We consider an arbitrary topological group $G$ definable in a structure $\mathcal M$, such that some basis for the topology of $G$ consists of sets definable in $\mathcal M$. To each such group $G$ we associate a compact $G$-space of…

Logic · Mathematics 2015-06-15 Ya'Acov Peterzil , Sergei Starchenko

In this article, we summarize the results on symmetric conformal geometries. We review the results following from the general theory of symmetric parabolic geometries and prove several new results for symmetric conformal geometries. In…

Differential Geometry · Mathematics 2016-02-08 Jan Gregorovič , Lenka Zalabová

In this note, we initiate a study of the finite-dimensional representation theory of a class of algebras that correspond to noncommutative deformations of compact surfaces of arbitrary genus. Low dimensional representations are investigated…

Representation Theory · Mathematics 2020-05-20 Joakim Arnlind

Let V(KG) be a normalised unit group of the modular group algebra of a finite p-group G over the field K of p elements. We introduce a notion of symmetric subgroups in V(KG) as subgroups invariant under the action of the classical…

Rings and Algebras · Mathematics 2008-01-08 A. B. Konovalov , A. G. Krivokhata

We use assembly maps to study $\mathbf{TC}(\mathbb{A}[G];p)$, the topological cyclic homology at a prime $p$ of the group algebra of a discrete group $G$ with coefficients in a connective ring spectrum $\mathbb{A}$. For any finite group, we…

K-Theory and Homology · Mathematics 2019-10-02 Wolfgang Lueck , Holger Reich , John Rognes , Marco Varisco

Let $S$ be an infinite-type surface and let $G \leq \operatorname{Map}(S)$ be a locally bounded Polish subgroup. We construct a metric graph $M$ of simple arcs and curves on $S$ preserved by the action of $G$ and for which the vertex orbit…

Geometric Topology · Mathematics 2025-08-12 Michael C. Kopreski , George Shaji