The realization conjecture for winding-number invariants of almost embeddings of K4K_4

From papers

Let K4K_4 be the complete graph on vertices 1,2,3,41,2,3,4, and let f:K4R2f:K_4\to\mathbb R^2 be an almost embedding. For an oriented cycle CC and a vertex vv, write wf(C,v)w_f(C,v) for the winding number of the image of CC about f(v)f(v). For j[4]j\in[4], set

wf(C1,1)=wf(234,1),wf(C2,2)=wf(134,2),wf(C3,3)=wf(124,3),wf(C4,4)=wf(123,4).\begin{aligned} w_f(C_1,1)&=w_f(234,1),\\ w_f(C_2,2)&=w_f(134,2),\\ w_f(C_3,3)&=w_f(124,3),\\ w_f(C_4,4)&=w_f(123,4). \end{aligned}

Realization conjecture. For any integers n1,n2,n3,n4n_1,n_2,n_3,n_4 whose sum is odd, there exists an almost embedding f:K4R2f:K_4\to\mathbb R^2 such that

wf(234,1)=n1,wf(134,2)=n2,wf(124,3)=n3,wf(123,4)=n4.w_f(234,1)=n_1,\quad w_f(134,2)=n_2,\quad w_f(124,3)=n_3,\quad w_f(123,4)=n_4.

This asserts that the parity condition supplied by the theorem that the corresponding signed sum is odd is the only restriction on these four winding numbers. The supplied text gives examples and references, but does not state whether the realization claim has been proved; its status is therefore left open.

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Sources & referencesView supporting material

Primary source

E. Alkin, A. Miroshnikov and A. Skopenkov, “Invariants of almost embeddings of graphs in the plane”, arXiv:2410.09860 (2026).

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