  Several mechanisms of density dependence of the s-wave repulsion in pionic
atoms, beyond the conventional model, are tested by parameter fits to a large
(106 points) set of data from $^{16}$O to $^{238}$U, including `deeply bound'
states in $^{205}$Pb. Special attention is paid to the proper choice of nuclear
density distributions. A density-dependent isovector scattering amplitude
suggested recently by Weise to result from a density dependence of the pion
decay constant is introduced and found to account for most of the so-called
anomalous repulsion. The presence of such an effect might indicate partial
chiral symmetry restoration in dense matter. The anomalous repulsion is fully
accounted for when an additional relativistic impulse approximation term is
included in the potential.
