is comparable – as predicted by Brown-Rho scale valid up to $\sim n_0$ – to the ratio $f_\pi (n_0)/f_\pi(0)\approx 0.80\approx \sqrt{\frac{\la\bar{q}q\ra
(n_0)}{\la\bar{q}q\ra}}$ found in deeply bound pionic atoms.

Other indirect indications for the dropping masses, such as for example the reduction of the nuclear tensor force etc., are summarized in the reviews [@BR:PR]. What may be a bit surprising is that nuclear physics has fared so successfully without ever invoking Brown-Rho scaling even though the vacuum change due to density is expected. As suggested in [@BR:PR], this may be understood in terms of a web of intricate “dualities" at low energy known variously as “quark-hadron continuity," “Cheshire Cat principle" etc., concepts that are yet to be put on a solid basis.

The import of the discussion in this subsection is that it illustrates how chiral symmetry property which is a basic property of QCD and Fermi-liquid property which is a mundane many-body effect can be compounded in $ordinary$ nuclear processes.

What the dileptons see
----------------------

Experimentalists in heavy ion physics purport to extract an in-medium “spectral function" of a vector meson quantum number, say, $\rho$ or $\omega$ as a function of invariant mass. This quantity is intended to tell us 