On the smallest trees with the same restricted $U$-polynomial and the rooted $U$-polynomial

The Circuit Polynomial of the Restricted Rooted Product G(Gamma) of Graphs with a Bipartite Core G

As an instance of the B-polynomial, the circuit, or cycle, polynomial P(G(Gamma); w) of the generalized rooted product G(Gamma) of graphs was studied by Farrell and Rosenfeld ({\em Jour. Math. Sci. (India)}, 2000, \textbf{11}(1), 35--47) and Rosenfeld and Diudea ({\em Internet Electron. J. Mol. Des.}, 2002, \textbf{1}(3), 142--156). In both cases, the rooted product G(Gamma) was considered without any restrictions on graphs G and Gamma. Herein, we present a new general result and its corollaries concerning the case when the core graph G is restricted to be bipartite. The last instance of G(Gam…

通用有根系统发育树形与通用缠结图

Universal rooted phylogenetic tree shapes and universal tanglegrams

本文研究有根二叉树和缠结图的通用结构规模，给出上下界并计算 n≤11 的最小通用树，部分结果推广到 d 叉情形。

Pattern restricted quasi-Stirling permutations

We define a variation of Stirling permutations, called quasi-Stirling permutations, to be permutations on the multiset $\{1,1,2,2,\ldots, n,n\}$ that avoid the patterns 1212 and 2121. Their study is motivated by a known relationship between Stirling permutations and increasing ordered rooted labeled trees. We construct a bijection between quasi-Stirling permutations and the set of ordered rooted labeled trees and investigate pattern avoidance for these permutations.

Restricted non-separable planar maps and some pattern avoiding permutations

Tutte founded the theory of enumeration of planar maps in a series of papers in the 1960s. Rooted non-separable planar maps are in bijection with West-2-stack-sortable permutations, beta(1,0)-trees introduced by Cori, Jacquard and Schaeffer in 1997, as well as a family of permutations defined by the avoidance of two four letter patterns. In this paper we give upper and lower bounds on the number of multiple-edge-free rooted non-separable planar maps. We also use the bijection between rooted non-separable planar maps and a certain class of permutations, found by Claesson, Kitaev and Steingrimss…

A conjecture of Baruah and Begum on the smallest parts function of restricted overpartitions

In 2017, Andrews, Dixit, Schultz and Yee introduced the function $\overline{\textrm{spt}}_ω(n)$, which denotes the number of smallest parts in the overpartitions of $n$ in which the smallest part is always overlined and all odd parts are less than twice the smallest part. Recently, Baruah and Begum established several internal congruences and congruences modulo small powers of $5$ for $\overline{\textrm{spt}}_ω(n)$. Moreover, they conjectured a family of internal congruences modulo any powers of $5$ and two families of congruences modulo any even powers of $5$. In this paper, we confirm three …

秩二拟阵 Ehrhart $h^*$-多项式的实根性与超对数凹性

Real-rootedness and ultra log-concavity of rank-two matroid Ehrhart $h^*$-polynomials

本文证明秩二拟阵在特定条件下Ehrhart $h^*$-多项式的实根性，给出反例否证猜想，并证明超对数凹性及单峰性。