Infrared Catastrophe for Nelson’s Model—Non-Existence of Ground State and Soft-Boson Divergence

Abstract

We mathematically study the infrared catastrophe for the Hamiltonian of Nelson’s model when it has the external potential in a general class. For the model, we prove the pull-through formula on ground states in operator theory first. Based on this formula, we show both non-existence of any ground state and divergence of the total number of soft bosons.