We probe for operators occurring in the APQCD (Abelian-projected QCD) action by evaluating Abelian-projected one-plaquette spectral densities in pure gauge SU(3) fixed to the maximal Abelian gauge. Couplings ${\overline{B}}_{\mathrm{APQCD}}\mathrm{}(q,L)\mathrm{}$ are extracted from the spectral densities for each representation $q$, $L\times L$ plaquette. We interpret our results to indicate that $q=L=1\mathrm{}$ plaquettes dominate the APQCD action. We also see evidence for weakly coupled $L=2\mathrm{}$ plaquettes in the APQCD action since the $L$ dependence of ${\overline{B}}_{\mathrm{APQCD}}\mathrm{}(q,L)\mathrm{}$ at $L=2\mathrm{}$ deviates from what is expected if the APQCD action had no $L=2\mathrm{}$ plaquettes. Moreover, a comparison of ${\overline{B}}_{\mathrm{APQCD}}$ to ${\overline{B}}_{\mathrm{QED}}$ from a numerical simulation of compact QED indicates that ${\overline{B}}_{\mathrm{APQCD}}\mathrm{}(1,1)>{\overline{B}}_{\mathrm{QED}}\mathrm{}(1,1)\mathrm{}$ even if ${\beta }_{\mathrm{QED}}>{\beta }_c$. Since ${\overline{B}}_{\mathrm{QED}}\mathrm{}(1,1)\mathrm{}$ monotonically increases with increasing ${\beta }_{\mathrm{QED}}$ and compact QED is not confining when ${\beta }_{\mathrm{QED}}>{\beta }_c$, the presence of $L>\mathrm{}1\mathrm{}$ operators is required if APQCD is confining.

• Received 28 September 1993

DOI:https://doi.org/10.1103/PhysRevD.49.2574