L-5

Goal : This is the first lecture about the dynamics of a disordered system. We will see that different systems display pinning until a critical threshold. We will revisit Larkin arguments and discuss the spectrum of excitation of the instabilities.

Pinning and depininng of a disordered material

In the first lectures we saw that a disorder system can be trapped in deep energy states and form a glass. Today we will see that disorder systems can be also pinned

a second phenomenon originated by dos

Disorder is also at the origin of pinning. Under the action of an external force, the sysyem resists to deformation in a way

of a complex energy landscape characterized by many minima (more or less deep), maxima and saddle points. An external force tilts this multidimansional landscape in a direction, Ho

are at the origin of glassy phases in .

minima

The energy landscape od disordered systems is not only caracterized by deep minima In $d=1$ we found $\theta =1/3$