Active Matter & Nuclear Physics

Making quantitative statements about biological systems is hard, mainly because they are inherently noisy, complex and messy and there seems to be no obvious way in which their description can be simplified. For this reason, models that yield accurate predictions at the level of experimental numbers tend to be few and far between across much of the biological sciences. Interestingly, however, our ability to accurately model a number of biophysical phenomena has increased dramatically in recent years. These new developments lie at the intersection of non-equilibrium statistical mechanics and soft condensed matter physics with biology. They draw from methods now referred to as "active matter" approaches.  I will begin by explaining the basic ideas that motivate the study of active matter, starting from simple examples.  I will then describe work from my group which uses these ideas to model the properties of the DNA within cell nuclei. Our work addresses, quantitatively, several long-standing questions about the architecture of the cell nucleus. Among these are questions of why chromosomes are found to be positioned non-randomly within nuclei, why chromosomes appear to form individual "territories", and what determines their shapes, sizes and a host of other properties. I hope to convey a feeling for why the following statement, familiar in slightly modified form to biologists, might be accurate: "Nothing in physical biology makes sense except in the light of non-equilibrium (active) processes".