Glassy dynamics have been observed in fields ranging from chemistry and physics to evolution, computer science, and biology. In contrast to a dilute solution, the interior of a living cell is crowded on many length scales. Recent experiments have measured subdiffusive motion of tracer particles in living bacterial cells, where a particle's mean-squared displacement grows sublinearly with time, as ~ tb . Experimentally, b is close to 2/3 and is robust to severe physiological perturbations. Is this value of b the result of evolutionary optimization or a mere coincidence? I will present a theory to answer this question and discuss how a subdiffusive environment might alter familiar concepts of chemical reactions in vivo.
In the second part of the talk, I will discuss the dynamics of a structural glass former. Dynamical heterogeneity, where particles separated by only a few molecular diameters relax on timescales that differ by orders of magnitude, is a hallmark of the glass transition. Two qualitatively different models of dynamic heterogeneity have come to dominate the discussion of supercooled liquids in the last few years. These two models borrow ideas from critical phenomena, and make different predictions for how the evolution of certain dynamical quantities depends on dimensionality. We have developed an atomistic model of a supercooled liquid in four spatial dimensions to test these predictions.