Dynamical reflection equation

We construct a dynamical reflection equation algebra, $\tilde{\mathcal{K}}$, via a dynamical twist of the ordinary reflection equation algebra. A dynamical version of the reflection equation is deduced as a corollary. We show that $\tilde{\mathcal{K}}$ is a right comodule algebra over a dynamical analog of the Faddeev-Reshetikhin-Takhtajan algebra equipped with a structure of right bialgebroid. We introduce dynamical trace and use it for constructing central elements of $\tilde{\mathcal{K}}$.