Weakly disordered absorbing-state phase transitions

The effects of quenched disorder on nonequilibrium phase transitions in the directed percolation universality class are revisited. Using a strong-disorder energy-space renormalization-group method, it is shown that for any amount of disorder the critical behavior is controlled by an infinite-randomness fixed point in the same universality class of the random transverse-field Ising models.

Figure 1

(Color online) Schematic decimation procedure.

Figure 2

(Color online) Time $\tau$ and length $\xi$ scales along the SDRG flow at criticality. Transition rates are drawn from boxlike distributions as indicated. Chains have $2\times {10}^6$ sites and the data were averaged over 100 disorder realizations. Error bars are about the symbol size.