1997/04/17 by Ferenc Pazmandi, Richard T. Scalettar, Gergely T. Zimanyi · 1 citation
Physics and Astronomy · #cond-mat.dis-nn #cond-mat.stat-mech
paper · pdf · doi:10.1103/physrevlett.79.5130
4 pages, Latex, one figure in .eps format
arxiv created 1997/04/17 · arxiv updated 2009/11/30
For phase transitions in disordered systems, an exact theorem provides a bound on the finite size correlation length exponent: νFS<= 2/d. It is believed that the true critical exponent νof a disorder induced phase transition satisfies the same bound. We argue that in disordered systems the standard averaging introduces a noise, and a corresponding new diverging length scale, characterized by νFS=2/d. This length scale, however, is independent of the system's own correlation length ξ. Therefore νcan be less than 2/d. We illustrate these ideas on two exact examples, with ν< 2/d. We propose a new method of disorder averaging, which achieves a remarkable noise reduction, and thus is able to capture the true exponents.