Formes mod\'er\'ement ramifi\'ees de polydisques ferm\'es et de dentelles

Let $k$ be a complete non-Archimedean field, $L$ a finite tamely ramified galoisian extension of $k$ and $X$ a $k$-analytic space. We show that $X$ is isomorphic to a closed $k$-polydisc (resp. a $k$-lace) if and only if $X_L$ is isomorphic to a closed $L$-polydisc (resp. a $L$-lace) on which the action of $\mathrm{G}\mathrm{a}\mathrm{l}(L\mathrm{/}k)$ is reasonable.