ELECTROMAGNETIC EMISSION RATES AND SPECTRAL SUM-RULES

The electromagnetic emission rates at SPS energies satisfy spectral co nstraints in leading order in the pion and nucleon densities. These co nstraints follow from the strictures of broken chiral symmetry. We sat urate these constraints using available data, leading to model indepen dent emission rates from a hadronic gas. With a simple fire-ball scena rio, only large nucleon densities may account for the present CERES da ta.