{
  "id": "1105.5020",
  "version": "v1",
  "published": "2011-05-25T13:30:48.000Z",
  "updated": "2011-05-25T13:30:48.000Z",
  "title": "A geometric approach to (g, k)-modules of finite type",
  "authors": [
    "Alexey Petukhov"
  ],
  "comment": "Ph.D. thesis, 73 pages, peacewise published",
  "categories": [
    "math.RT",
    "math.SG"
  ],
  "abstract": "Let $g$ be a semisimple Lie algebra over $\\mathbb C$ and $k$ be a reductive in $g$ subalgebra. We say that a simple $g$-module $M$ is a $(g; k)$-module if as a $k$-module $M$ is a direct sum of finite-dimensional $k$-modules. We say that a simple $(g; k)$-module $M$ is of finite type if all $k$-isotypic components of $M$ are finite-dimensional. To a simple $g$-module $M$ one assigns interesting invariants V$(M)$, $\\EuScript V(M)$ and L$(M)$ reflecting the 'directions of growth of M'. In this work we prove that, for a given pair $(g; k)$, the set of possible such invariants is ?finite. Let $K$ be a reductive Lie group with Lie algebra $k$. We say that a $K$-variety $X$ is $K$-spherical if $X$ has an open orbit of a Borel subgroup of $K$. Let $W$ be a fi?nite-dimensional $K$-module. The set of flags ($W_1,..., W_s)$ of $W$ with fi?xed dimensions $(n_1;...; ns)$ is a homogeneous space of the group GL(W). We call such a variety partial $W$-flag variety. In this work we classify all $K$-spherical partial $W$-flag varieties. We say that a simple $(g; k)$-module is bounded if there exists constant C$_M$ such that, for any simple $k$-module $E$, the isotypic component of $E$ in $M$ is a direct sum of not more than C$_M$-copies of $E$. To any simple sl$(W)$-module one assigns a partial $W$-flag variety. In this thesis we prove that a simple (sl$(W); k$)-module is bounded if and only if the corresponding partial $W$-flag variety is $K$-spherical. Moreover, we prove that the pair (sl$(W); k$) admits an infin? ite-dimensional simple bounded module if and only if P$(W)$ is a $K$-spherical variety. For four particular case we say more about category of bounded modules and the set of simple bounded modules.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2011-05-25T13:30:48.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "finite type",
      "flag variety",
      "geometric approach",
      "direct sum",
      "isotypic component"
    ],
    "tags": [
      "dissertation"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 73,
      "language": "en",
      "license": "arXiv",
      "status": "editable",
      "adsabs": "2011arXiv1105.5020P"
    }
  }
}