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zhao-vanishing

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Revision 284 · 2026-09-30 05:09 UTC
atlas import import · claude-opus-5-5
“Written for the atlas by Claude Opus 5.5 at the direction of Danielle Fong (content/wiki/Statement__zhao-vanishing.md).”

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+---
+title: Zhao's vanishing conjecture
+short: VC — for Hessian-nilpotent quartic P, Δᵐ Pᵐ⁺¹ = 0 for large m
+symbol: VC
+kind: conjecture
+status: refuted
+tier: V3
+year: 2007
+authors: W. Zhao (arXiv 2004; Trans. AMS 2007)
+statement: Let $\Delta$ be the Laplacian on $\mathbb C[z_1,\dots,z_n]$. If $P$ is homogeneous of degree 4 and $\Delta^mP^m=0$ for all $m\ge1$ (equivalently, $P$ is Hessian nilpotent), then $\Delta^mP^{m+1}=0$ for all large $m$.
+---
+By the symmetric reduction, the Jacobian conjecture reduces to gradient maps $z-\nabla P$ with $P$ a Hessian-nilpotent homogeneous quartic ([[uses::Statement:de-bondt-van-den-essen-symmetric|Zhao's argument starts from the de Bondt–van den Essen symmetric form]]). Zhao wrote the formal inverse of such a map as $z+\nabla Q$, where $Q$ is a series in the terms $\Delta^mP^{m+1}$. So [[uses::Statement:formal-inverse|the map has a polynomial inverse exactly when those terms vanish for large m, which is a statement about the formal inverse]]. The result is that [[equivalent-to::Statement:jc-n|the vanishing conjecture in every dimension is equivalent to the Jacobian conjecture in every dimension]].<ref name="z">W. Zhao, [Hessian nilpotent polynomials and the Jacobian conjecture](https://arxiv.org/abs/math/0409534), Trans. Amer. Math. Soc. 359 (2007) 249–274.</ref> The equivalence does not preserve the dimension, because it passes through the cubic-homogeneous and symmetric reductions.
 
+It is VC for the Laplacian and $Q=P$; the general form allows other constant-coefficient operators and test polynomials, so [[special-case-of::Statement:generalized-vanishing|VC is a special case of the generalized vanishing conjecture]].<ref>A. van den Essen, [An introduction to Mathieu subspaces](https://arxiv.org/abs/1907.06107), arXiv:1907.06107 (2019).</ref>
+ 
+**It is false.** Through the equivalence, the July 2026 counterexample makes VC fail in some finite dimension. Explicit failures came in August: Prellberg states that it fails for the 40- and 38-variable [[Statement:gradient-keller-counterexamples|gradient counterexamples]]. The smallest failing dimension is unknown. Zhang's note of 20 July asks for a small explicit instance.<ref>Z. Zhang, [Direct Consequences of the Three-Dimensional Counterexample to the Jacobian Conjecture](https://zzhang-iu.github.io/papers/direct-consequences-jacobian/), 20 July 2026.</ref>
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Revision 284 as rendered

By the symmetric reduction, the Jacobian conjecture reduces to gradient maps z−∇Pz-\nabla P with PP a Hessian-nilpotent homogeneous quartic (Zhao's argument starts from the de Bondt–van den Essen symmetric form). Zhao wrote the formal inverse of such a map as z+∇Qz+\nabla Q, where QQ is a series in the terms ΔmPm+1\Delta^mP^{m+1}. So the map has a polynomial inverse exactly when those terms vanish for large m, which is a statement about the formal inverse. The result is that the vanishing conjecture in every dimension is equivalent to the Jacobian conjecture in every dimension.[1] The equivalence does not preserve the dimension, because it passes through the cubic-homogeneous and symmetric reductions.

It is VC for the Laplacian and Q=PQ=P; the general form allows other constant-coefficient operators and test polynomials, so VC is a special case of the generalized vanishing conjecture.[2]

It is false. Through the equivalence, the July 2026 counterexample makes VC fail in some finite dimension. Explicit failures came in August: Prellberg states that it fails for the 40- and 38-variable gradient counterexamples. The smallest failing dimension is unknown. Zhang's note of 20 July asks for a small explicit instance.[3]

  1. ↑ W. Zhao, Hessian nilpotent polynomials and the Jacobian conjecture, Trans. Amer. Math. Soc. 359 (2007) 249–274.
  2. ↑ A. van den Essen, An introduction to Mathieu subspaces, arXiv:1907.06107 (2019).
  3. ↑ Z. Zhang, Direct Consequences of the Three-Dimensional Counterexample to the Jacobian Conjecture, 20 July 2026.