The Whitehead-product kernel conjecture for shrinking wedges

Let n2n\geq 2 and let

X=\bigcurlyveekNXkX=\bigcurlyvee_{k\in\mathbb{N}}X_k

be a shrinking wedge of finite (n1)(n-1)-connected CW-complexes. Let σ:Xj=1Xj\sigma:X\to\prod_{j=1}^{\infty}X_j be the inclusion map. Whitehead-product kernel conjecture. Then

W2n1(X)=ker(σ#:π2n1(X)π2n1(j=1Xj)).\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 π2n1(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 (n1)(n-1)-connected CW-complexes, but that new deformation methods are needed to prove it in general.

Sources & referencesView supporting material

Primary source

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

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