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Representation Theory

Published by the American Mathematical Society, the Representation Theory (ERT) is devoted to research articles of the highest quality in all areas of pure and applied mathematics.

ISSN 1088-4165

The 2020 MCQ for Representation Theory is 0.7.

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The Capelli identity for Grassmann manifolds
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by Siddhartha Sahi PDF
Represent. Theory 17 (2013), 326-336 Request permission

Abstract:

The column space of a real $n\times k$ matrix $x$ of rank $k$ is a $k$-plane. Thus we get a map from the space $X$ of such matrices to the Grassmannian $\mathbb {G}$ of $k$-planes in $\mathbb {R}^{n}$, and hence a $GL_{n}$-equivariant isomorphism \[ C^{\infty }\left ( \mathbb {G}\right ) \approx C^{\infty }\left ( X\right ) ^{GL_{k}}\text {.} \] We consider the $O_{n}\times GL_{k}$-invariant differential operator $C$ on $X$ given by \[ C=\det \left ( x^{t}x\right ) \det \left ( \partial ^{t}\partial \right ),\quad \text {where }x=\left ( x_{ij}\right ),\text { }\partial =\left ( \frac {\partial }{\partial x_{ij}}\right ). \] By the above isomorphism, $C$ defines an $O_{n}$-invariant operator on $\mathbb {G}$.

Since $\mathbb {G}$ is a symmetric space for $O_{n}$, the irreducible $O_{n}$-submodules of $C^{\infty }\left ( \mathbb {G}\right )$ have multiplicity 1; thus, $O_{n}$-invariant operators act by scalars on these submodules. Our main result determines these scalars for a general class of such operators including $C$. This answers a question raised by Howe and Lee and also gives new Capelli-type identities for the orthogonal Lie algebra.

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Additional Information
  • Siddhartha Sahi
  • Affiliation: Department of Mathematics, Rutgers University, New Brunswick, New Jersey
  • MR Author ID: 153000
  • Email: sahi@math.rutgers.edu
  • Received by editor(s): April 28, 2012
  • Received by editor(s) in revised form: December 13, 2012
  • Published electronically: June 7, 2013
  • © Copyright 2013 American Mathematical Society
    The copyright for this article reverts to public domain 28 years after publication.
  • Journal: Represent. Theory 17 (2013), 326-336
  • MSC (2010): Primary 22E46, 43A90
  • DOI: https://doi.org/10.1090/S1088-4165-2013-00434-X
  • MathSciNet review: 3063840