Radical ideal formulation of the Casas–Alvero conjecture

Let KK be an algebraically closed field of characteristic zero, let dd be a positive integer, and let f=xd+a1xd1++ad1xK[a1,,ad1][x]f=x^d+a_1x^{d-1}+\cdots+a_{d-1}x\in K[a_1,\ldots,a_{d-1}][x]. For i{1,,d1}i\in\{1,\ldots,d-1\}, let

Ri=Res(f,Hi(f))K[a1,,ad1],R_i=\operatorname{Res}(f,H_i(f))\in K[a_1,\ldots,a_{d-1}],

where Hi(f)H_i(f) is the ii-th Hasse derivative of ff.

Nullstellensatz formulation of the Casas–Alvero conjecture. The conjecture is equivalent to

(R1,,Rd1)=(a1,,ad1),\sqrt{(R_1,\ldots,R_{d-1})}=(a_1,\ldots,a_{d-1}),

or, equivalently, there is some NNN\in\mathbb{N} such that

aiN(R1,,Rd1)for all i{1,,d1}.a_i^N\in(R_1,\ldots,R_{d-1})\quad\text{for all }i\in\{1,\ldots,d-1\}.

This is an algebraic reformulation of the preceding Casas–Alvero conjecture rather than a separate mathematical claim. Over non-algebraically closed fields, the source notes that this formulation is a priori stronger than the corresponding statement about the KK-rational zero set.

Sources & referencesView supporting material

Primary source

Daniel Schaub and Mark Spivakovsky, “A note on the Casas-Alvero Conjecture”, arXiv:2312.08742 (2025).

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