Criteria of positivity for linear maps constructed from permutation pairs

Abstract

In this paper, we show that a $D$-type map $\Phi_D:M_n\rightarrow M_n$ with $D=(n-2)I_n+P_{\pi_1}+P_{\pi_2}$ induced by a pair $\{\pi_1,\pi_2\}$ of permutations of $(1,2,..., n)$ is positive if $\{\pi_1,\pi_2\}$ has property (C). The property (C) is characterized for $\{\pi_1,\pi_2\}$, and an easy criterion is given for the case that $\pi_1=\pi^p$ and $\pi_2=\pi^q$, where $\pi$ is the permutation defined by $\pi(i)=i+1$ mod $n$ and $1\leq p<q\leq n$.