Plebanski complex

Fuente: arXiv
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Autori principali: Krasnov, Kirill, Shaw, Adam
Natura: Preprint
Pubblicazione: 2025
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author Krasnov, Kirill
Shaw, Adam
author_facet Krasnov, Kirill
Shaw, Adam
contents As is very well-known, linearisation of the instanton equations on a 4-manifold gives rise to an elliptic complex of differential operators, the truncated (twisted) Hodge complex $Λ^0(\mathfrak{g}) \to Λ^1(\mathfrak{g})\to Λ^2_+(\mathfrak{g})$. Moreover, the linearisation of the full YM equations also fits into this framework, as it is given by the second map followed by its adjoint. We define and study properties of what we call the Plebański complex. This is a differential complex that arises by linearisation of the equations implying that a Riemannian 4-manifold is hyper-Kähler. We recall that these are most naturally stated as the condition that there exists a perfect $Σ^i\wedge Σ^j\simδ^{ij}$ triple $Σ^i, i=1,2,3$ of 2-forms that are closed $dΣ^i=0$. The Riemannian metric is encoded by the 2-forms $Σ^i$. We show that what results is an elliptic differential complex $TM \to S\to E\times Λ^1 \to E$, where $S$ is the tangent space to the space of perfect triples, and $E=\mathbb{R}^3$. We also show that, as in the case with instanton equations, the full Einstein equations $Ric=0$ also fit into this framework, their linearisation being given by the second map followed by its adjoint. Our second result concerns the elliptic operator that the Plebański complex defines. In the case of the instanton complex, operators appearing in the complex supplemented with their adjoints assemble to give the Dirac operator. We show how the same holds true for the Plebański complex. Supplemented by suitable adjoints, operators assemble into an elliptic operator that squares to the Laplacian and is given by the direct sum of two Dirac operators.
format Preprint
id arxiv_https___arxiv_org_abs_2502_19027
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Plebanski complex
Krasnov, Kirill
Shaw, Adam
Differential Geometry
General Relativity and Quantum Cosmology
High Energy Physics - Theory
As is very well-known, linearisation of the instanton equations on a 4-manifold gives rise to an elliptic complex of differential operators, the truncated (twisted) Hodge complex $Λ^0(\mathfrak{g}) \to Λ^1(\mathfrak{g})\to Λ^2_+(\mathfrak{g})$. Moreover, the linearisation of the full YM equations also fits into this framework, as it is given by the second map followed by its adjoint. We define and study properties of what we call the Plebański complex. This is a differential complex that arises by linearisation of the equations implying that a Riemannian 4-manifold is hyper-Kähler. We recall that these are most naturally stated as the condition that there exists a perfect $Σ^i\wedge Σ^j\simδ^{ij}$ triple $Σ^i, i=1,2,3$ of 2-forms that are closed $dΣ^i=0$. The Riemannian metric is encoded by the 2-forms $Σ^i$. We show that what results is an elliptic differential complex $TM \to S\to E\times Λ^1 \to E$, where $S$ is the tangent space to the space of perfect triples, and $E=\mathbb{R}^3$. We also show that, as in the case with instanton equations, the full Einstein equations $Ric=0$ also fit into this framework, their linearisation being given by the second map followed by its adjoint. Our second result concerns the elliptic operator that the Plebański complex defines. In the case of the instanton complex, operators appearing in the complex supplemented with their adjoints assemble to give the Dirac operator. We show how the same holds true for the Plebański complex. Supplemented by suitable adjoints, operators assemble into an elliptic operator that squares to the Laplacian and is given by the direct sum of two Dirac operators.
title Plebanski complex
topic Differential Geometry
General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2502.19027