Energetics and geometry of excitations in random systems

Methods for studying droplets in models with quenched disorder are critically examined. Low-energy excitations in two-dimensional models an investigated by finding minimal energy interior excitations and by computing the effect of bulk perturbations. The numerical data support the assumptions of compact droplets and a single exponent for droplet energy scaling. Analytic calculations show how strong corrections to power laws can result when samples and droplets are averaged over. Such corrections can explain apparent discrepancies in several previous numerical results for spin glasses.