Screening mass from chiral perturbation theory, virial expansion, and the lattice.

We calculate the electric screening mass in hot hadronic matter using two different approaches, chiral perturbation theory and the relativistic virial expansion with empirical phase shifts, and compare the results to each other and to a gas of free pions and [rho] mesons. We also compute the electric screening mass for noninteracting, charged bosons with mass [ital m] on a lattice to study likely finite size effects in lattice gauge theory simulations of continuum QCD. For a lattice of given size, the continuum can be properly represented only for a window in the ratio [ital T]/[ital m].