Weak ergodicity breaking and aging in disordered systems

We present a phenomenological model for the dynamics of disordered (complex) systems. We postulate that the lifetimes of the many metastable states are distributed according to a broad, power law probability distribution. We show that aging occurs in this model when the average lifetime is infinite. A simple hypothesis leads to a new functional form for the relaxation which is in remarkable agreement with spin-glass experiments over nearly five decades in time.