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 Title: The Frobenius direct image of line bundles and the structure of representations Author(s): Reed, Mary Lynn Doctoral Committee Chair(s): Haboush, William J. Department / Program: Mathematics Discipline: Mathematics Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Mathematics Abstract: In the representation theory of semisimple algebraic groups in positive characteristic, the induced line bundles, ${\cal L}$($\lambda$), on the flag variety G/B, are important objects of study. E.g., their global sections form representations of G which are dual to the Weyl modules. In this thesis, our central object of study is the direct image of the induced line bundles under the Frobenius morphism. I.e., $F\sb\*{\cal L}$($\lambda$). We study the homogeneous sheaf structure of $F\sb\*{\cal L}$($\lambda$) in the context of several celebrated representation theory problems. Specifically, our decomposition of the Frobenius direct image on the projective line provides a geometric interpretation of the structure of SL(2,k) Weyl modules. In addition, $F\sb\*{\cal L}$($\lambda$) is a homogeneous sheaf induced by a restricted Verma module. As a generalization of the decomposition of $F\sb\*{\cal L}$($\lambda$) on the projective line, we have discovered some remarkable complexes of restricted Verma modules for the group SL(3,k). These complexes are quite clearly related to the Bernstein-Gel'fand-Gel'fand resolution in characteristic zero. And as the Bernstein-Gel'fand-Gel'fand resolution provides an elegant proof of the Weyl character formula, our complexes provide a procedure for calculating the characters of the irreducible representations as sums of Weyl characters. Therefore, the question of the existence of such complexes for any semisimple simply connected algebraic group in positive characteristic is closely related to the search for a character formula for the irreducible representation. Issue Date: 1995 Type: Text Language: English URI: http://hdl.handle.net/2142/21997 Rights Information: Copyright 1995 Reed, Mary Lynn Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9543702 OCLC Identifier: (UMI)AAI9543702
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