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The hidden hallmarks of nonequilibrium
Systems with disparate timescales are ubiquitous in physics and biology. Efficient modeling requires to restrict the description to the slower degrees of freedom by means of a systematic, controlled elimination of fast variables. I will discuss this general issue in stochastic systems with multiple timescales. I will show how, in the presence of nonequilibrium, vestiges of the fast dynamics remain in the effective, slow evolution — even in the limit of infinitely large scale-separation — thereby crippling the attempt at a description of the full system in terms of slow variables only.