We consider the cluster algebra associated to the $Q$-system for $A_r$ as a tool for relating $Q$-system solutions to all possible sets of initial data. We show that the conserved quantities of the $Q$-system are partition functions for hard particles on particular target graphs with weights, which are determined by the choice of initial data. This allows us to interpret the simplest solutions of the Q-system as generating functions for Viennot's heaps on these target graphs, and equivalently as generating functions of weighted paths on suitable dual target graphs. The generating functions take the form of finite continued fractions. In this setting, the cluster mutations correspond to local rearrangements of the fractions which leave their final value unchanged. Finally, the general solutions of the $Q$-system are interpreted as partition functions for strongly non-intersecting families of lattice paths on target lattices. This expresses all cluster variables as manifestly positive Laurent polynomials of any initial data, thus proving the cluster positivity conjecture for the $A_r$ $Q$-system. We also give an alternative formulation in terms of domino tilings of deformed Aztec diamonds with defects.
Sums of binomial determinants, non-intersecting lattice paths and positivity of Chern-Schwartz-MacPherson classes
我们给出了一个Chern-Schwartz-MacPherson类的正性猜想的组合解释，正如P. P. Schiffi和作者在以前的论文中所述。它转化为一个积极的性质，由二项式系数组成的p乘p行列式的总和，推广经典的Lindstrom-Gessel-Viennot定理等。我们证明了这个猜想p= 2，3。
Lattice paths and branched continued fractions: An infinite sequence of generalizations of the Stieltjes--Rogers and Thron--Rogers polynomials, with coefficientwise Hankel-total positivity
An explicit formula for Koornwinder moments and Rains' positivity conjecture
Sungkyunkwan University（成均馆大学）；Ewha Womans University（梨花女子大学）；Research Center for Mathematics and Interdisciplinary Sciences, Shandong University（山东大学数学与交叉科学研究中心）；Yonsei University（延世大学）
School of Mathematics and Statistics, Beijing Institute of Technology（北京理工大学数学与统计学院）；MIIT Key Laboratory of Mathematical Theory and Computation in Information Security, Beijing Institute of Technology（北京理工大学工业和信息化部信息安全数学理论与计算重点实验室）
本文研究了联图的色对称函数，通过组合方法得到了几种图类的色对称函数展开式，并提出了帽链的 e 正猜想。
