  We explore higher-derivative terms in the low-energy effective action for the
dilaton, the Goldstone boson of spontaneously broken scale invariance. Focusing
on the simplest holographic realization of spontaneously broken scale
invariance, the Randall-Sundrum (RS) scenario, we identify the nonlinear action
for the RS dilaton by integrating out Kaluza-Klein graviton modes. The
coefficient of a particular four-derivative dilaton self-interaction can be
identified with the Weyl $a$-anomaly of the dual conformal field theory, which
we use to verify anomaly matching arguments. We also find novel, $a$-dependent
couplings of the dilaton to light matter fields. These anomalous interactions
can have a significant effect on the collider phenomenology and the cosmology,
potentially allowing us to probe the structure of the underlying conformal
sector via low-energy physics. The dilaton effective theory also serves as an
interesting scalar analog of gravity, and we study solutions to the equation of
motion that parallel black holes and cosmologies.
