Approximation of Schr{\"o}dinger Unitary Groups of Operators by Particular Projection Methods

In this paper we work with the approximation of unitary groups of operators of the form $e^{-itH}$ where $H\in \mathcal{L}(\mathcal{H})$ is the Hamiltonian of a given quantum dynamical system modeled in the discretizable Hilbert space $\mathcal{H}=\mathcal{H}(G)$, to perform such approximations we implement some techniques from operator theory that we name particular projection methods by compatibility with quantum theory conventions. Once particular representations are defined we study the interelation between some of them properties with the original operators that they mimic. In the end some estimates for numerical implementation are presented to verify the theoretical discussion.