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Let $p$ be a prime, and let $\pi_\ast^{(p)}$ be the ring of stable homotopy groups of spheres localized at the prime $p$. This is a nonnegatively-graded-commutative ring with $\mathbb Z_{(p)}$ in degree zero, and nilpotent torsion everywhere else. It's a horrible, non-Noetherian ring.

Question: What is the Goldie dimension (aka uniform dimension) of the ring $\pi_\ast^{(p)}$?

Here, the Goldie dimension is the maximal number $n$ such that there exist $n$ ideals $I_1,\dots,I_n \subseteq \pi_\ast^{(p)}$ such that the induced map of modules $I_1 \oplus \cdots \oplus I_n \to \pi_\ast^{(p)}$ is injective.

Notes:

  • To say that the Goldie dimension is 1 is to say that any two nonzero ideals have nonzero intersection, so in order to rule out this case it would suffice to find two nonzero ideals in $\pi_\ast^{(p)}$ whose intersection is zero.

  • For more on Goldie dimension, see Lam's Lectures on Modules and Rings, Chapter 6.

  • I expect that the answer is probably $\infty$, but maybe not. The answer is $\infty$ if we do not localize at a prime, because $\oplus_p \pi_{\geq 1}^{(p)} \to \pi_\ast^s$ is an injection.

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    $\begingroup$ I have a recollection that a paper on the generating hypothesis says: if the generating hypothesis holds, then any two nonzero elements in the stable stems have a nonzero element that they both divide. So this would assert dimension 1. (But the generating hypothesis is completely up in the air.) $\endgroup$ Commented Nov 30, 2023 at 23:57
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    $\begingroup$ Ah, got it. It is apparently Proposition 9.3 in Freyd's "Stable homotopy" from 1966, and this was generalized by D. W. Kahn in "Relations in stable homotopy modules" in 1973. $\endgroup$ Commented Dec 1, 2023 at 4:04

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