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In mathematics, in particular in differential geometry, mathematical physics, and representation theory a Weitzenböck identity, named after Roland Weitzenböck, expresses a relationship between two second-order elliptic operators on a manifold with the same leading symbol. (The origins of this terminology seem doubtful, however, as there does not seem to be any evidence that such identities ever appeared in Weitzenböck's work.) Usually Weitzenböck formulae are implemented for ''G''-invariant self-adjoint operators between vector bundles associated to some principal ''G''-bundle, although the precise conditions under which such a formula exists are difficult to formulate. Instead of attempting to be completely general, then, this article presents three examples of Weitzenböck identities: from Riemannian geometry, spin geometry, and complex analysis. ==Riemannian geometry== In Riemannian geometry there are two notions of the Laplacian on differential forms over an oriented compact Riemannian manifold ''M''. The first definition uses the divergence operator δ defined as the formal adjoint of the de Rham operator ''d'': :: where α is any ''p''-form and β is any (''p'' + 1)-form, and is the metric induced on the bundle of (''p'' + 1)-forms. The usual form Laplacian is then given by :: On the other hand, the Levi-Civita connection supplies a differential operator :: where Ωp''M'' is the bundle of ''p''-forms and ''T'' *M is the cotangent bundle of ''M''. The Bochner Laplacian is given by :: where is the adjoint of . The Weitzenböck formula then asserts that :: where ''A'' is a linear operator of order zero involving only the curvature. The precise form of ''A'' is given, up to an overall sign depending on curvature conventions, by :: where : *''R'' is the Riemann curvature tensor, : * Ric is the Ricci tensor, : * is the map that takes the wedge product of a 1-form and p-form and gives a (p+1)-form, : * is the universal derivation inverse to θ on 1-forms. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Weitzenböck identity」の詳細全文を読む スポンサード リンク
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