$J$-Stability of immediately expanding polynomial maps in $p$-adic dynamics

Given a family $\{ f_{\lambda} \}_{\lambda \in \Lambda}$ of polynomial maps of degree $d$ where $\Lambda$ is the set of parameters, a polynomial map $f_{\lambda_0}$ is called {\it $J$-stable in $\Lambda$} if there exists a neighborhood of $\lambda_0$ in $\Lambda$ such that for any element $\lambda$ in the neighborhood, there exists a conjugacy between the dynamics on the Julia sets of $f_\lambda$ and $f_{\lambda_0}$. The aim of this paper is to show that a polynomial map $f_{\lambda_0}$ over the field $\mathbb{C}_p$ of $p$-adic complex numbers is $J$-stable in the family of polynomial maps over $\mathbb{C}_p$ if $f_{\lambda_0}$ is {\it immediately expanding}.