Itaru Sasaki Ground State Energy of the Polaron in the Relativistic Quantum Electrodynamics (215K, PDF) ABSTRACT. We consider the polaron model in the relativistic quantum electrodynamics(QED). We prove that the ground state energy of the model is finite for all values of the fine-structure constant and the ultraviolet cutoff. Moreover we give an upper bound and a lower bound of the ground state energy.