On bound states in Quantum Field Theory

In this paper, a new method to describe the energy spectrums of bound states in Quantum Field Theory is presented. We point out that the fundamental field and its dual soliton combine together to form bound states and the soliton corresponds to the ghost particle in our regularization scheme which takes advantage of dimensional regularization and Pauli-Villars regularization. Based on this point of view, we discuss the bound states of massive Thirring model, the positronium ($e^+e^-$) in QED and the vector meson in QCD. We also give a new way to obtain the mass of soliton (quantum soliton) from the stationary condition (gap equation). Our results agree with experimental data to high precision. We argue that the hypothetic $X_{17}$ particle in decay of $\rm{{}^8 Be}$ and $\rm{{}^4 He}$ is a soliton. For vector meson, we find the squared masses of $\rho$ resonances are $m^2(n)\sim (an^{1/3}-b)^2$ which coincide well with experiments.