  The yielding of foams, concentrated emulsions, pastes and other soft
materials under applied strain is often characterized by measuring the complex
shear modulus as a function of strain amplitude at low frequency. Results
obtained for materials of different physico-chemical constitution are
strikingly similar, suggesting the presence of a generic mechanism as pointed
out in several previous theoretical studies. We show that the observed strain
dependence of the complex shear modulus can be interpreted as the consequence
of elasto-plastic response.
