  The notion that the scalar listed as $f_0 (500)$ in the particle data booklet
is a pseudo-Nambu-Goldstone (NG) boson of spontaneously broken scale symmetry,
explicitly broken by a small departure from an infrared fixed point, is
explored in nuclear dynamics. That notion which puts the scalar -- that we
shall identify as a "dilaton" -- on the same footing as the pseudo-scalar
pseudo-NG bosons, i.e., octet $\pi$, while providing a simple explanation for
the $\Delta I=1/2$ rule for kaon decay, generalizes the standard chiral
perturbation theory (S$\chi$PT) to "scale chiral perturbation theory," denoted
$\chi$PT$_\sigma$, with {\it one infrared mass scale for both symmetries}, with
the $\sigma$ figuring as a chiral singlet NG mode in non-strange sector.
Applied to nuclear dynamics, it is seen to provide possible answers to various
hitherto unclarified nuclear phenomena such as the success of
one-boson-exchange potentials (OBEP), the large cancellation of strongly
attractive scalar potential by strongly repulsive vector potential in
relativistic mean field theory of nuclear systems and in-medium QCD sum rules,
the interplay of the dilaton and the vector meson $\omega$ in dense skyrmion
matter, the BPS skyrmion structure of nuclei accounting for small binding
energies of medium-heavy nuclei, and the suppression of hyperon degrees of
freedom in compact-star matter.
