4 papers
On the maximum twist width of delta-matroids
Xian'an Jin, Zhuo Li, Qi Yan +1
For a ribbon graph , let denote its Euler genus. Recently, Chen, Gross and Tucker [J. Algebraic Combin. 63 (2026) 13] derived a formula for the maximum partial-dual Euler…
Matrix Quasi-tree Theorem
Qingying Deng, Xian'an Jin, Qi Yan +1
Building on prior work that established Matrix Quasi-tree Theorems for special embedded graphs, in this paper, we develop a comprehensive theory applicable to all embedded graphs.…
Proof of a conjecture of Fomichev and Karev
Qi Yan, Qingying Deng, Xian'an Jin
We prove a conjecture of Fomichev and Karev [{European J. Combin.} 127 (2025) 104160] by showing the equality of two graph invariants: , defined via graph colorings, and , de…
Orbits and self-twuality in set systems and delta-matroids
Zhuo Li, Xian'an Jin, Qi Yan
We introduce a new group action on set systems, constructed as a semidirect product of a permutation group and a group generated by twist and loop complementation operations on a s…