Abstract: The dynamics of nonequilibrium spatially extended systems are often dominated by fluctuations, e.g., due
to deterministic chaos or intrinsic stochasticity. This reflects into generic scale invariant or kinetic roughening
behavior that can be classified into universality classes defined by critical exponent values and by the probability distribution function (PDF) of field fluctuations. Suitable geometrical constraints are known to change secondary features of the PDF while keeping the values of the exponents unchanged, inducing universality subclasses. Working on the Kuramoto-Sivashinsky equation as a paradigm of spatiotemporal chaos, we show that the physical nature of the prevailing fluctuations (chaotic or stochastic) can also change the universality class while respecting the exponent values, as the PDF is substantially altered. This transition takes place at a nonzero value of the stochastic noise amplitude and may be suitable for experimental verification.
