Barcode-interval bound in arbitrary homological degree

Prove that for every filtration of flag complexes on n vertices, the number of intervals in its degree-k persistence barcode is at most the k-th Betti number of the flag complex of the Turán graph \(\mathcal{T}_{n,k+1}\).

Background

The paper establishes sharp extremal results for individual Betti numbers and, in homological degree one, for the maximal number of barcode intervals. It does not establish the analogous interval-count bound in arbitrary homological degree k. The proposed inequality would extend the degree-one result by relating the number of persistent homology intervals to the extremal Betti number realized by the Turán graph Tn,k+1\mathcal{T}_{n,k+1}.

References

However, many questions remain open, and we propose the following conjectures. If \mathcal{G} is a filtration on n vertices, then the number of intervals in the barcode of \mathcal{G} in homology degree k satisfies |B_k(\mathcal{G})| \leq \beta_k(\mathcal{T}_{n,k+1}).

Extremal Betti Numbers and Persistence in Flag Complexes  (2502.21294 - Beers et al., 28 Feb 2025) in Section 6, Discussion