The Whitehead-product kernel conjecture for shrinking wedges

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Let n≥2n\geq 2 and let

X=\bigcurlyveek∈NXkX=\bigcurlyvee_{k\in\mathbb{N}}X_k

be a shrinking wedge of finite (n−1)(n-1)-connected CW-complexes. Let σ:X→∏j=1∞Xj\sigma:X\to\prod_{j=1}^{\infty}X_j be the inclusion map. Whitehead-product kernel conjecture. Then

W2n−1(X)=ker⁡(σ#:π2n−1(X)→π2n−1(∏j=1∞Xj)).\mathcal{W}_{2n-1}(X)=\ker\bigl(\sigma_{\#}:\pi_{2n-1}(X)\to\pi_{2n-1}(\prod_{j=1}^{\infty}X_j)\bigr).

The conjecture asserts that every element of π2n−1(X)\pi_{2n-1}(X) that becomes trivial in the product is accounted for by the subgroup generated by the relevant Whitehead products. The preceding discussion indicates that this is expected for shrinking wedges of finite (n−1)(n-1)-connected CW-complexes, but that new deformation methods are needed to prove it in general.

References

Primary source

Jeremy Brazas, “Identities for Whitehead products and infinite sums”, arXiv:2408.10430 (2025).

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