  We explore several potential issues that have been raised over the years
regarding the "entropic droplet" scenario of activated transport in liquids,
due to Wolynes and coworkers, with the aim of clarifying the status of various
approximations of the random first order transition theory (RFOT) of the
structural glass transition. In doing so, we estimate the mismatch penalty
between alternative aperiodic structures, above the glass transition; the
penalty is equal to the typical magnitude of free energy fluctuations in the
liquid. The resulting expressions for the activation barrier and the
cooperativity length contain exclusively bulk, static properties; in their
simplest form they contains only the bulk modulus and the configurational
entropy per unit volume. The expressions are universal in that they do not
depend explicitly on the molecular detail. The predicted values for the barrier
and cooperativity length and, in particular, the temperature dependence of the
barrier are in satisfactory agreement with observation. We thus confirm that
the entropic droplet picture is indeed not only internally-consistent but is
also fully constructive, consistent with the apparent success of its many
quantitative predictions. A simple view of a glassy liquid as a locally
metastable, degenerate pattern of frozen-in stress emerges in the present
description. Finally, we derive testable relationships between the bulk modulus
and several characteristics of glassy liquids and peculiarities in
low-temperature glasses.
