scholarly journals Equivariant images of projective space under the action of SL (n, ℤ)

1981 ◽  
Vol 1 (4) ◽  
pp. 519-522 ◽  
Author(s):  
Robert J. Zimmer
Keyword(s):  
Normal Subgroup ◽  
Projective Space ◽  
Lie Group ◽  
Measure Space ◽  
Irreducible Lattice ◽  
Group 3 ◽  
Higher Rank ◽  
Measure Class

The point of this note is to answer in the affirmative a question of G. A. Margulis. In the course of his proof of the finiteness of either the cardinality or the index of a normal subgroup of an irreducible lattice in a higher rank semi-simple Lie group [3], [4], Margulis proves that if Γ = SL (n, ℤ),n≥3, (X, μ) is a measurable Γ-space, μ quasi-invariant, and φ: ℙn−1→Xis a measure class preserving Γ-map, then either φ is a measure space isomorphism or μ is supported on a point. Margulis then asks whether the topological analogue of this result is true. This is answered in the following.

scholarly journals Some groups with T1 primitive ideal spaces

1985 ◽  
Vol 38 (1) ◽  
pp. 55-64 ◽  
Author(s):  
A. L. Carey ◽  
W. Moran
Keyword(s):  
Normal Subgroup ◽  
Lie Groups ◽  
Lie Group ◽  
Locally Compact Group ◽  
Primitive Ideal ◽  
Ideal Space ◽  
Solvable Lie Groups ◽  
Locally Compact ◽  
Simply Connected ◽  
Connected Lie Group

AbstractLet G be a second countable locally compact group possessing a normal subgroup N with G/N abelian. We prove that if G/N is discrete then G has T1 primitive ideal space if and only if the G-quasiorbits in Prim N are closed. This condition on G-quasiorbits arose in Pukanzky's work on connected and simply connected solvable Lie groups where it is equivalent to the condition of Auslander and Moore that G be type R on N (-nilradical). Using an abstract version of Pukanzky's arguments due to Green and Pedersen we establish that if G is a connected and simply connected Lie group then Prim G is T1 whenever G-quasiorbits in [G, G] are closed.

scholarly journals Sphere and projective space of a C*-algebra with a faithful state

2019 ◽  
Vol 52 (1) ◽  
pp. 410-427
Author(s):  
Andrea C. Antunez
Keyword(s):  
Initial Data ◽  
Projective Space ◽  
Banach Spaces ◽  
Lie Group ◽  
Unit Sphere ◽  
Homogeneous Spaces ◽  
Inner Product ◽  
C Algebra ◽  
Faithful State ◽  
Banach Lie Group

AbstractLet 𝒜 be a unital C*-algebra with a faithful state ϕ. We study the geometry of the unit sphere 𝕊ϕ = {x ∈ 𝒜 : ϕ(x*x) = 1} and the projective space ℙϕ = 𝕊ϕ/𝕋. These spaces are shown to be smooth manifolds and homogeneous spaces of the group 𝒰ϕ(𝒜) of isomorphisms acting in 𝒜 which preserve the inner product induced by ϕ, which is a smooth Banach-Lie group. An important role is played by the theory of operators in Banach spaces with two norms, as developed by M.G. Krein and P. Lax. We define a metric in ℙϕ, and prove the existence of minimal geodesics, both with given initial data, and given endpoints.

Non-abelian cohomology of abelian Anosov actions

2000 ◽  
Vol 20 (1) ◽  
pp. 259-288 ◽  
Author(s):  
ANATOLE KATOK ◽  
VIOREL NIŢICĂ ◽  
ANDREI TÖRÖK
Keyword(s):  
Discrete Time ◽  
Lie Group ◽  
Global Information ◽  
Infinite Dimensional ◽  
Anosov Actions ◽  
Geometric Character ◽  
Higher Rank ◽  
Real Analytic ◽  
A New Technique ◽  
Discrete Time Case

We develop a new technique for calculating the first cohomology of certain classes of actions of higher-rank abelian groups (${\mathbb Z}^k$ and ${\mathbb R}^k$, $k\ge 2$) with values in a linear Lie group. In this paper we consider the discrete-time case. Our results apply to cocycles of different regularity, from Hölder to smooth and real-analytic. The main conclusion is that the corresponding cohomology trivializes, i.e. that any cocycle from a given class is cohomologous to a constant cocycle. The principal novel feature of our method is its geometric character; no global information about the action based on harmonic analysis is used. The method can be developed to apply to cocycles with values in certain infinite dimensional groups and to rigidity problems.

scholarly journals A 2-dimensional algebraic variety with 27 rectilinear generators and 108 trisecants and its connection with the maximal exceptional simple lie group

2005 ◽  
Vol 77 (91) ◽  
pp. 61-65
Author(s):  
Boris Rosenfeld
Keyword(s):  
Projective Space ◽  
Algebraic Variety ◽  
Lie Group ◽  
Regular Configuration ◽  
Dimensional Projective Space

A 2-dimensional algebraic variety in 4-dimensional projective space determining a regular configuration is considered and its connection with simple exceptional Lie group E8 is found.

On geometry of orbits of adapted projective frame space

2019 ◽  
pp. 88-98
Author(s):  
A. Kuleshov
Keyword(s):  
Normal Subgroup ◽  
Projective Space ◽  
Tangent Space ◽  
Affine Group ◽  
Current Paper ◽  
Previous Issue ◽  
Distinguished Point

The current paper continues consideration of geometry of projective frame orbits started in the author’s article in the previous issue. The ndimensional projective space with a distinguished point (the center) is considered. The action of matrix affine group of order n on the adapted projective frame manifold is given. It is shown that the linear frames, i. e., bases of the tangent space, can be identified with the orbits of adapted projective frames under the action of some normal subgroup of this group. Two adapted frames are said to be equivalent if they belong to the same orbit. The strict perspectivity relation between two adapted frames is introduced. The proofs of the theorem on the Desargues hyperplane and of the criterion of equivalence are simplified. According to this criterion, two adapted frames in strict perspective are equivalent if and only if the Desargues hyperplane generated by these frames is passing through the center.

scholarly journals Expanding Cone and Applications to Homogeneous Dynamics

2019 ◽  
Author(s):  
Ronggang Shi
Keyword(s):  
Normal Subgroup ◽  
Homogeneous Space ◽  
Lie Group ◽  
Error Rate ◽  
Spectral Gap ◽  
General Setting ◽  
Semisimple Lie Group ◽  
Homogeneous Dynamics ◽  
Maximal Split ◽  
Split Torus

Abstract Let $U$ be a horospherical subgroup of a noncompact simple Lie group $H$ and let $A$ be a maximal split torus in the normalizer of $U$. We define the expanding cone $A_U^+$ in $A$ with respect to $U$ and show that it can be explicitly calculated. We prove several dynamical results for translations of $U$-slices by elements of $A_U^+$ on a finite volume homogeneous space $G/\Gamma $ where $G$ is a Lie group containing $H$. More precisely, we prove quantitative nonescape of mass and equidistribution of a $U$-slice. If $H$ is a normal subgroup of $G$ and the $H$ action on $G/\Gamma $ has a spectral gap, we prove effective multiple equidistribution and pointwise equidistribution with an error rate. In this paper, we formulate the notion of the expanding cone and prove the dynamical results above in the more general setting where $H$ is a semisimple Lie group without compact factors. In the appendix, joint with Rene Rühr, we prove a multiple ergodic theorem with an error rate.

Corrections to ‘Invariant measures for higher-rank hyperbolic abelian actions’

1998 ◽  
Vol 18 (2) ◽  
pp. 503-507 ◽  
Author(s):  
A. KATOK ◽  
R. J. SPATZIER
Keyword(s):  
Lie Group ◽  
Invariant Measures ◽  
Unique Ergodicity ◽  
Weyl Chamber ◽  
Total Measure ◽  
Additional Information ◽  
Zero Entropy ◽  
Entropy Factor ◽  
Higher Rank ◽  
Translation Subgroup

The proofs of Theorems 5.1 and 7.1 of [2] contain a gap. We will show below how to close it under some suitable additional assumptions in these theorems and their corollaries. We will assume the notation of [2] throughout. In particular, $\mu$ is a measure invariant and ergodic under an $R^k$-action $\alpha$. Let us first explain the gap. Both theorems are proved by establishing a dichotomy for the conditional measures of $\mu$ along the intersection of suitable stable manifolds. They were either atomic or invariant under suitable translation or unipotent subgroups $U$. Atomicity eventually led to zero entropy. Invariance of the conditional measures showed invariance of $\mu$ under $U$. We then claimed that $\mu$ was algebraic using, respectively, unique ergodicity of the translation subgroup on a rational subtorus or Ratner's theorem (cf. [2, Lemma 5.7]). This conclusion, however, only holds for the $U$-ergodic components of $\mu$ which may not equal $\mu$. In fact, in the toral case, the $R^k$-action may have a zero-entropy factor such that the conditional measures along the fibers are Haar measures along a foliation by rational subtori. Since invariant measures with zero entropy have not been classified, we cannot conclude algebraicity of the total measure $\mu$ at this time. In the toral case, the existence of zero entropy factors turns out to be precisely the obstruction to our methods. The case of Weyl chamber flows is somewhat different as the ‘Haar’ direction of the measure may not be integrable. In this case, we need to use additional information coming from the semisimplicity of the ambient Lie group to arrive at the versions of Theorem 7.1 presented below.

Lifting homotopies through fixed points II

1984 ◽  
Vol 96 (3-4) ◽  
pp. 201-205 ◽  
Author(s):  
M. A. Armstrong
Keyword(s):  
Normal Subgroup ◽  
Fixed Points ◽  
Lie Group ◽  
Hausdorff Space ◽  
Final Section ◽  
Invariant Subgroup ◽  
Compact Lie Group ◽  
Discontinuous Group ◽  
Group Of Homeomorphisms ◽  
Path Connected

SynopsisThis note complements an earlier paper of the same title. Let G be a discontinuous group of homeomorphisms of a connected, locally path connected, Hausdorff space X, and let ∏:X → X/G denote the associated projection. We work relative to a G-invariant subgroup H of the fundamental group of X and investigate the quotient group ∏1(X/G)/∏*(H). By choosing H appropriately, we can calculate ∏1(X/G) and show that ∏1(X/G)/∏*(∏1(X)) is isomorphic to G/F, where F is the normal subgroup of G generated by those elements which have fixed points. In a final section, we give analogous results for actions of a compact Lie group.

Highly Symmetric Homogeneous Spaces

1974 ◽  
Vol 26 (02) ◽  
pp. 291-293 ◽  
Author(s):  
L. N. Mann
Keyword(s):  
Projective Space ◽  
Lie Group ◽  
Closed Subgroup ◽  
Homogeneous Spaces ◽  
Real Projective Space ◽  
Standard Sphere ◽  
Connected Lie Group ◽  
Trivial Subgroup

We consider effective homogeneous spacesM=G/HwhereGis a compact connected Lie group,His a closed subgroup andGacts effectively onM(i.e.,Hcontains no non-trivial subgroup normal inG). It is known that dimG≦m2/2 +m/2 wherem= dimMand that if dimG=m2/2 +m/2, thenMis diffeomorphic to the standard sphereSmor the standard real projective spaceRPm[1]. In addition it has been shown that for fixedmthere are gaps in the possible dimensions forGbelow the maximal bound [4; 5].

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