Abstract:The classical notions of Riemannian and Hermitian symmetric spaces have recently been extended to CR manifolds by W. Kaup and the reviewer [Adv. Math. 149 (2000), no. 2, 145--181; MR1742704 (2000m:32044)]. Here, in order to contain natural examples such as spheres, one has to appropriately weaken the notion of symmetry by requiring that its differential at the reference point be the negative identity only in the complex tangent directions (and possibly other directions if the CR manifold is not of finite type)… Show more
“…In [8] we proved the implications (b) ⇒ (c) and (b) ⇒ (a), and classified all parabolic minimal CR algebras satisfying (b). Moreover, the last assertions of Theorem 3.2 summarize results that are already proved there.…”
Section: Statement Of the Resultsmentioning
confidence: 92%
“…The endomorphisms ρ(A), for A ∈ g ∩ q, commute with J and hence ρ(g ∩ q) is a Lie algebra of complex endomorphisms of H. This J is called the partial complex structure of (g, q). According to [8], we say that (g, q) has Property (J) if there existsJ ∈ g ∩ q such that ρ(J) = J.…”
Section: Statement Of the Resultsmentioning
confidence: 99%
“…Proof As we already observed in [8], condition (C) means that : for each α ∈ ∩ R • the connected component of α in B ∩ R • is one of the following:…”
Section: Lemma 52 Ifmentioning
confidence: 90%
“…section 2).We can also assume (see [1,8]) that R + ⊂ Q, for the parabolic set of roots Q = {α | g α ⊂ q} associated to q.…”
Section: Proposition 41 a Necessary Condition Formentioning
confidence: 97%
“…In Theorem 8.1 of [8], we characterized property (J) by the requirement that the cross marked Satake diagram (S, ) of our fundamental parabolic minimal CR algebra (g, q) satisfies some properties, that we called (A), (B), (C) there. Thus the proof will consist in showing that a) implies that (A), (B), (C) are valid.…”
Complementing the results of (Lotta and Nacinovich, Adv. Math. 191(1): 114-146, 2005), we show that the minimal orbit M of a real form G of a semisimple complex Lie group G C in a flag manifold M = G C /Q is CR-symmetric (see (Kaup and Zaitsev Adv. Math. 149(2):145-181, 2000)) if and only if the corresponding CR algebra (g, q) admits a Z 2 gradation compatible with the CR structure.
“…In [8] we proved the implications (b) ⇒ (c) and (b) ⇒ (a), and classified all parabolic minimal CR algebras satisfying (b). Moreover, the last assertions of Theorem 3.2 summarize results that are already proved there.…”
Section: Statement Of the Resultsmentioning
confidence: 92%
“…The endomorphisms ρ(A), for A ∈ g ∩ q, commute with J and hence ρ(g ∩ q) is a Lie algebra of complex endomorphisms of H. This J is called the partial complex structure of (g, q). According to [8], we say that (g, q) has Property (J) if there existsJ ∈ g ∩ q such that ρ(J) = J.…”
Section: Statement Of the Resultsmentioning
confidence: 99%
“…Proof As we already observed in [8], condition (C) means that : for each α ∈ ∩ R • the connected component of α in B ∩ R • is one of the following:…”
Section: Lemma 52 Ifmentioning
confidence: 90%
“…section 2).We can also assume (see [1,8]) that R + ⊂ Q, for the parabolic set of roots Q = {α | g α ⊂ q} associated to q.…”
Section: Proposition 41 a Necessary Condition Formentioning
confidence: 97%
“…In Theorem 8.1 of [8], we characterized property (J) by the requirement that the cross marked Satake diagram (S, ) of our fundamental parabolic minimal CR algebra (g, q) satisfies some properties, that we called (A), (B), (C) there. Thus the proof will consist in showing that a) implies that (A), (B), (C) are valid.…”
Complementing the results of (Lotta and Nacinovich, Adv. Math. 191(1): 114-146, 2005), we show that the minimal orbit M of a real form G of a semisimple complex Lie group G C in a flag manifold M = G C /Q is CR-symmetric (see (Kaup and Zaitsev Adv. Math. 149(2):145-181, 2000)) if and only if the corresponding CR algebra (g, q) admits a Z 2 gradation compatible with the CR structure.
We investigate the nondegeneracy of higher order Levi forms on weakly nondegenerate homogeneous CR manifolds. Improving previous results, we prove that general orbits of real forms in complex flag manifolds have order less or equal than 3 and the compact ones less or equal 2. Finally we construct by Lie extensions weakly nondegenerate CR vector bundles with arbitrary orders of nondegeneracy.
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