  We develop a new method to isolate localized defects from extended
vibrational modes in disordered solids. This method augments particle
interactions with an artificial potential that acts as a high-pass filter: it
preserves small-scale structures while pushing extended vibrational modes to
higher frequencies. The low-frequency modes that remain are "bare" defects;
they are exponentially localized without the quadrupolar tails associated with
elastic interactions. We demonstrate that these localized excitations are
excellent predictors of plastic rearrangements in the solid. We characterize
several of the properties of these defects that appear in mesoscopic theory of
plasticity, including their distribution of energy barriers, number density,
and size, which is a first step in testing and revising continuum models for
plasticity in disordered solids.
