Dynamical scaling in a two-dimensional lattice model of chaotic maps, in
contact with a thermal bath, is numerically studied. The model here proposed is
equivalent to a conserved Ising model with coupligs which fluctuate over the
same time scale as spin moves. When couplings fluctuations and thermal
fluctuations are both important, this model does not belong to the class of
universality of a Langevin equation known as model B; the scaling exponents are
continuously varying with the temperature and depend on the map used. The
universal behavior of model B is recovered when thermal fluctuations are
dominant.Comment: 6 pages, 4 figures. Revised version accepted for publication on
Physical Review E as a Rapid Communicatio