Expand all Collapse all | Results 1 - 8 of 8 |
1. CJM 2013 (vol 65 pp. 1287)
$K$-theory of Furstenberg Transformation Group $C^*$-algebras The paper studies the $K$-theoretic invariants of the crossed product
$C^{*}$-algebras associated with an important family of homeomorphisms
of the tori $\mathbb{T}^{n}$ called Furstenberg transformations.
Using the Pimsner-Voiculescu theorem, we prove that given $n$, the
$K$-groups of those crossed products, whose corresponding $n\times n$
integer matrices are unipotent of maximal degree, always have the same
rank $a_{n}$. We show using the theory developed here that a claim
made in the literature about the torsion subgroups of these $K$-groups
is false. Using the representation theory of the simple Lie algebra
$\frak{sl}(2,\mathbb{C})$, we show that, remarkably, $a_{n}$ has a
combinatorial significance. For example, every $a_{2n+1}$ is just the
number of ways that $0$ can be represented as a sum of integers
between $-n$ and $n$ (with no repetitions). By adapting an argument
of van Lint (in which he answered a question of ErdÅs), a simple,
explicit formula for the asymptotic behavior of the sequence
$\{a_{n}\}$ is given. Finally, we describe the order structure of the
$K_{0}$-groups of an important class of Furstenberg crossed products,
obtaining their complete Elliott invariant using classification
results of H. Lin and N. C. Phillips.
Keywords:$K$-theory, transformation group $C^*$-algebra, Furstenberg transformation, Anzai transformation, minimal homeomorphism, positive cone, minimal homeomorphism Categories:19K14, 19K99, 46L35, 46L80, , 05A15, 05A16, 05A17, 15A36, 17B10, 17B20, 37B05, 54H20 |
2. CJM 2009 (vol 62 pp. 382)
Verma Modules over Quantum Torus Lie Algebras Representations of various one-dimensional central
extensions of quantum tori (called quantum torus Lie algebras) were
studied by several authors. Now we define a central extension of
quantum tori so that all known representations can be regarded as
representations of the new quantum torus Lie algebras $\mathfrak{L}_q$. The
center of $\mathfrak{L}_q$ now is generally infinite dimensional.
In this paper, $\mathbb{Z}$-graded Verma modules $\widetilde{V}(\varphi)$ over $\mathfrak{L}_q$
and their corresponding irreducible highest weight modules
$V(\varphi)$ are defined for some linear functions $\varphi$.
Necessary and sufficient conditions for $V(\varphi)$ to have all
finite dimensional weight spaces are given. Also necessary and
sufficient conditions for Verma modules $\widetilde{V}(\varphi)$ to
be irreducible are obtained.
Categories:17B10, 17B65, 17B68 |
3. CJM 2008 (vol 60 pp. 88)
Nilpotent Conjugacy Classes in $p$-adic Lie Algebras: The Odd Orthogonal Case We will study the following question: Are nilpotent conjugacy
classes of reductive Lie algebras over $p$-adic fields
definable? By definable, we mean definable by a formula in Pas's
language. In this language, there are no field extensions and no
uniformisers. Using Waldspurger's parametrization, we answer in the
affirmative in the case of special orthogonal Lie algebras
$\mathfrak{so}(n)$ for $n$ odd, over $p$-adic fields.
Categories:17B10, 03C60 |
4. CJM 2004 (vol 56 pp. 293)
Structure of modules induced from simple modules with minimal annihilator We study the structure of generalized Verma modules over a
semi-simple complex finite-dimensional Lie algebra, which are
induced from simple modules over a parabolic subalgebra. We consider
the case when the annihilator of the starting simple module is a
minimal primitive ideal if we restrict this module to the Levi factor of
the parabolic subalgebra. We show that these modules correspond to
proper standard modules in some parabolic generalization of the
Bernstein-Gelfand-Gelfand category $\Oo$ and prove that the blocks of
this parabolic category are equivalent to certain blocks of the
category of Harish-Chandra bimodules. From this we derive, in
particular, an irreducibility criterion for generalized Verma modules.
We also compute the composition multiplicities of those simple
subquotients, which correspond to the induction from simple modules
whose annihilators are minimal primitive ideals.
Keywords:parabolic induction, generalized Verma module, simple module, Ha\-rish-\-Chand\-ra bimodule, equivalent categories Categories:17B10, 22E47 |
5. CJM 2001 (vol 53 pp. 225)
Tensor Product Realizations of Simple Torsion Free Modules Let $\calG$ be a finite dimensional simple Lie algebra over the
complex numbers $C$. Fernando reduced the classification of infinite
dimensional simple $\calG$-modules with a finite dimensional weight
space to determining the simple torsion free $\calG$-modules for
$\calG$ of type $A$ or $C$. These modules were determined by Mathieu
and using his work we provide a more elementary construction realizing
each one as a submodule of an easily constructed tensor product module.
Category:17B10 |
6. CJM 1998 (vol 50 pp. 1323)
L'invariant de Hasse-Witt de la forme de Killing Nous montrons que l'invariant de Hasse-Witt de la forme de Killing
d'une alg{\`e}bre de Lie semi-simple $L$ s'exprime {\`a} l'aide de
l'invariant de Tits de la repr{\'e}sentation irr{\'e}ductible de
$L$ de poids dominant $\rho=\frac{1}{2}$ (somme des racines
positives), et des invariants associ{\'e}s au groupe des
sym{\'e}tries du diagramme de Dynkin de $L$.
Categories:11E04, 11E72, 17B10, 17B20, 11E88, 15A66 |
7. CJM 1998 (vol 50 pp. 816)
Tableaux realization of generalized Verma modules We construct the tableaux realization of generalized Verma modules
over the Lie algebra $\sl(3,{\bbd C})$. By the same procedure we
construct and investigate the structure of a new family of
generalized Verma modules over $\sl(n,{\bbd C})$.
Categories:17B35, 17B10 |
8. CJM 1998 (vol 50 pp. 266)
The torsion free Pieri formula Central to the study of simple infinite dimensional
$g\ell(n, \Bbb C)$-modules having finite dimensional weight spaces are the
torsion free modules. All degree $1$ torsion free modules are known.
Torsion free modules of arbitrary degree can be constructed by tensoring
torsion free modules of degree $1$ with finite dimensional simple modules.
In this paper, the central characters of such a tensor product module are
shown to be given by a Pieri-like formula, complete reducibility is
established when these central characters are distinct and an example
is presented illustrating the existence of a nonsimple indecomposable
submodule when these characters are not distinct.
Category:17B10 |