出版社:SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要:The signature of bound state formation on the lattice is of particular interest in this talk. In the
finite volume, where all states have discrete energies, it is rather hard to distinguish between a
bound state and a scattering state if the bound state were close to threshold, i.e. like a “loosely
bound state”. To study bound states in the finite volume, we calculate the positronium spectroscopy
in the Higgs phase of U(1) gauge dynamics, where the photon is massive and then
massive photons give rise to the short-ranged interparticle force. We try to identify bound state
formation on the basis of the L¨uscher’s finite size method, which suggests specific volume dependences
of the energy gap/shift from the threshold energy for either bound states or scattering
states.