  The mechanical behaviors of polycrystalline solids are determined by the
interplay between phenomena governed by two different thermodynamic
temperatures: the configurational effective temperature that controls the
density of dislocations, and the ordinary kinetic-vibrational temperature that
controls activated depinning mechanisms and thus deformation rates. This paper
contains a review of the effective-temperature theory and its relation to
conventional dislocation theories. It includes a simple illustration of how
these two thermal effects can combine to produce a predictive theory of spatial
heterogeneities such as shear-banding instabilities. Its main message is a plea
that conventional dislocation theories be reformulated in a thermodynamically
consistent way so that the vast array of observed behaviors can be understood
systematically.
