Power law fluctuations and scale free spatial patterns are known to
characterize steady state plastic flow in crystalline materials. In this Letter
we study the emergence of correlations in a simple Frenkel-Kontorova (FK) type
model of 2D plasticity which is largely free of arbitrariness, amenable to
analytical study and is capable of generating critical exponents matching
experiments. Our main observation concerns the possibility to reduce continuum
plasticity to an integer valued automaton revealing inherent discreteness of
the plastic flow.Comment: 4 pages, 5 figure