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An extremal theorem for positive curvature of graphs
Kaizhe Chen, Shiping Liu, Zhe You
We prove an extremal theorem for positive Ollivier/Lin--Lu--Yau curvature: every graph of order \(n\geq 8\) with more than \[ T(n)=\frac{n^2-3n}{2}-\left\lceil\frac{n}{2}\right\rce…
Criteria on forbidden subgraphs in the complements for positive Lin--Lu--Yau curvature
Kaizhe Chen, Shiping Liu, Zhe You
We investigate forbidden subgraph conditions in the complement of a graph that guarantee positive Lin--Lu--Yau curvature. In particular, we prove that every graph whose complement…
Books versus Triangles near the n/6 Threshold
Kaizhe Chen, Jie Ma, Tianhen Wang
The book number of a graph is the maximum number of triangles sharing a common edge. A strengthening of Mantel's theorem due to Rademacher states that every -vertex g…
On Lichnerowicz sharp distance-regular graphs
Kaizhe Chen, Shiping Liu, Heng Zhang
The first non-zero Laplacian eigenvalue of a finite graph is bounded below by its minimum Lin--Lu--Yau curvature . This is a discrete analogue of the classical Lichnerowic…
Edge-connectivity of graphs with non-negative Bakry-Émery curvature and amply regular graphs
Kaizhe Chen, Jack H. Koolen, Shiping Liu
We establish a sharp edge-connectivity estimate for graphs with non-negative Bakry-Émery curvature. This leads to a geometric criterion for the existence of a perfect matching. Pre…
Halin graphs with positive Lin-Lu-Yau curvature
Kaizhe Chen, Huiqiu Lin, Shiping Liu +1
Halin graphs constitute an interesting class of planar and polyhedral graphs. A generalized Halin graph is obtained by connecting all leaves of a planar embedding of a tree via a c…