Weak interactions in a background of a uniform magnetic field. A mathematical model for the inverse beta decay.I

In this paper we consider a mathematical model for the inverse beta decay in a uniform magnetic field. With this model we associate a Hamiltonian with cutoffs in an appropriate Fock space. No infrared regularization is assumed. The Hamiltonian is selfadjoint and has a ground state. We study its essential spectrum and determine its spectrum. Conditions for uniqueness of ground state are given. The coupling constant is supposed suffciently small.