TOPICS
Search

Generalized Hypergraph 4-Cycle


A generalized hypergraph 4-cycle is an r-uniform hypergraph consisting of four distinct hyperedges A, B, C, and D such that A union B=C union D and A intersection B=C intersection D=emptyset.

Let f_r(n) be the maximum number of hyperedges in an n-vertex r-uniform hypergraph containing no generalized hypergraph 4-cycle. Huang et al. (2026) proved that, for every fixed r>=4 and all sufficiently large n,

 f_r(n)=(n-1; r-1)+|_(n-1)/r_|,

where |_x_| is the floor function. Every extremal example is a full r-uniform star together with a maximum-cardinality collection of pairwise disjoint hyperedges on the other n-1 vertices, called a matching. When r|n, a second type is obtained by deleting the star hyperedge through the r-1 unmatched noncentral vertices and adding the r-set formed by these vertices and one graph vertex from the matching. The corresponding problem for r=3 remains open.


See also

Graph Cycle, Hyperedge, Hypergraph

Explore with Wolfram|Alpha

References

Huang, H.; Ma, J.; and Yang, T. "Extremal Hypergraphs Without Generalized 4-Cycles." 29 Sep 2026. https://arxiv.org/abs/2609.37744.

Cite this as:

Weisstein, Eric W. "Generalized Hypergraph 4-Cycle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/GeneralizedHypergraph4-Cycle.html

Subject classifications