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Journal ArticleDOI

Connection blocking in $$\text {SL}(n,\mathbb {R})$$ SL ( n , R ) quotients

Mohammadreza Bidar
- 11 Apr 2020 - 
- Vol. 209, Iss: 1, pp 135-148
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TLDR
In this paper, the authors show that the obtained quotient homogeneous spaces are not finitely blockable and that the set of non-blackable pairs is a dense subset of the homogeneous space M 2 times M 2.
Abstract
Let G be a connected Lie group and $$\varGamma \subset G$$ a lattice. Connection curves of the homogeneous space $$M=G/\varGamma $$ are the orbits of one parameter subgroups of G. To block a pair of points $$m_1,m_2 \in M$$ is to find a finite set $$B \subset M{\setminus } \{m_1, m_2 \}$$ such that every connecting curve joining $$m_1$$ and $$m_2$$ intersects B. The homogeneous space M is blockable if every pair of points in M can be blocked. In this paper we investigate blocking properties of $$M_n= \text {SL}(n,\mathbb {R})/\varGamma $$ , where $$\varGamma =\text {SL}(n,\mathbb {Z})$$ is the integer lattice. We focus on $$M_2$$ and show that the set of non blackable pairs is a dense subset of $$M_2 \times M_2$$ , and we conclude manifolds $$M_n$$ are not blockable. Finally, we review a quaternionic structure of $$\text {SL}(2,\mathbb {R})$$ and a way for making co-compact lattices in this context. We show that the obtained quotient homogeneous spaces are not finitely blockable.

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References
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BookDOI

Discrete subgroups of semisimple Lie groups

TL;DR: The Structure of the Book as discussed by the authors is a collection of essays about algebraic groups over arbitrary fields, including a discussion of the relation between the structure of closed subgroups and property (T) of normal subgroups.
Book

Introduction to Arithmetic Groups

TL;DR: A good introduction to the study of arithmetic subgroups of semisimple Lie groups can be found in this article, where the authors provide primers on lattice subgroups, arithmetic groups, real rank and Q-rank, ergodic theory, unitary representations, amenability, and quasi-isometries.
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Journal ArticleDOI

Growth of the number of geodesics between points and insecurity for Riemannian manifolds

TL;DR: Gromov and Mane as discussed by the authors proved that the number of geodesics with length between every pair of points in a uniformly secure Riemannian manifold grows polynomially as $T \to \infty.
Journal ArticleDOI

Blocking of billiard orbits and security for polygons and flat surfaces

TL;DR: In this article, the notion of security for polygons and flat surfaces was introduced and studied, and it was shown that a lattice polygon is secure iff it is arithmetic.