Kai Zheng

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math.CO2020

Stack-Sorting with Consecutive-Pattern-Avoiding Stacks

Colin Defant, Kai Zheng

We introduce consecutive-pattern-avoiding stack-sorting maps $SC_{σ}$ , which are natural generalizations of West's stack-sorting map $s$ and natural analogues of the classical…

math.CO2020

On the $e$ -positivity of trees and spiders

Kai Zheng

We prove that for any tree with a vertex of degree at least six, its chromatic symmetric function is not $e$ -positive, that is, it cannot be written as a nonnegative linear combina…

math.CO2020

Unitary Signings and Induced Subgraphs of Cayley Graphs of $Z_{2}^{n}$

Noga Alon, Kai Zheng

Let $G$ be a Cayley graph of the elementary abelian $2$ -group $Z_{2}^{n}$ with respect to a set $S$ of size $d$ . We prove that for any such $G, S$ and $d$ , the maximum degre…

Stack-Sorting with Consecutive-Pattern-Avoiding Stacks

On the e-positivity of trees and spiders

Unitary Signings and Induced Subgraphs of Cayley Graphs of Z2n​

On the $e$ -positivity of trees and spiders

Unitary Signings and Induced Subgraphs of Cayley Graphs of $Z_{2}^{n}$