Balanced versus lopsided All-Edges Sparse Triangle

Determine whether the balanced version of All-Edges Sparse Triangle requires near-$m^{4/3}$ time even though the lopsided version admits faster algorithms; equivalently, establish whether a faster algorithm for lopsided instances can coexist with the conjectured hardness of balanced instances.

Background

The paper’s main algorithm exploits a tripartite graph with two large parts and a substantially smaller middle part. It does not improve the balanced case, which is the target of several lower-bound reductions and is conjectured to require m4/3−o(1)m^{4/3-o(1)} time. The authors explicitly ask whether the observed separation between the two parameter regimes is genuine.

References

Is it possible that the lopsided version has a faster algorithm but the balanced version does not?

— Truly Subquadratic 3SUM and Truly Subcubic APSP via Triangles in Sparse Lopsided Graphs  (2610.06783 - Alman et al., 5 Oct 2026) in Section 8, Section “Conclusion,” paragraph “Fine-grained complexity”