Find a counterexample to the universal \(n+m\) minimal-width formula

Construct a pair of integers \(n,m\) with \(1\leq m\leq n\) for which the minimal width of ReLU networks is strictly less than \(n+m\), or otherwise determine whether the equality \(w_{\mathrm{min}(n,m)}=n+m\) holds throughout this range.

Background

For ReLU networks, the paper proves that the minimal width equals n+mn+m when n∈{2,3,4,7,8}n\in\{2,3,4,7,8\} and 1≤m≤n1\leq m\leq n, using smooth immersions of real projective spaces. The authors state that they do not expect this formula to hold for every pair in the broader range 1≤m≤n1\leq m\leq n, but they do not provide a counterexample. They note that the equality is already known to fail when m>2n≥4m>2n\geq4, leaving the stated range as an unresolved question.

References

We do not expect that the formula $w_{\text{min}(n,m) = n+m$ holds for all values of $n, m$ with $1 \le m \le n$, although we cannot yet provide a counterexample.

— The minimal width of neural networks and immersions of real projective space  (2610.20229 - Chu et al., 14 Oct 2026) in Section 1, Introduction