GAUGE-BALL SPECTRUM OF THE 4-DIMENSIONAL PURE U(1) GAUGE-THEORY

We investigate the continuum limit of the gauge-ball spectrum in the f our-dimensional pure U(1) lattice gauge theory. In the confinement pha se we identify various states scaling with the correlation length expo nent nu similar or equal to 0.35. The square root of the string tensio n also scales with this exponent, which agrees with the non-Gaussian f ixed point exponent recently found in the finite-size studies of this theory, Possible scenarios for constructing a non-Gaussian continuum t heory with the observed gauge-ball spectrum are discussed. The 0(++) s tate, however, scales with a Gaussian value nu similar or equal to 0.5 . This suggests the existence of a second, Gaussian continuum limit in the confinement phase and also the presence of a light or possibly ma ssless scalar in the non-Gaussian continuum theory. In the Coulomb pha se we find evidence for a few gauge balls, being resonances in multi-p hoton channels; they seem to approach the continuum limit with as yet unknown critical exponents, The maximal value of the renormalized coup ling in this phase is determined and its universality confirmed. (C) 1 997 Elsevier Science B.V.