Research

The study of how interactions among species lead to changes in their populations -- where species may refer to animals and plants in a forest, or microbes in a culture, or mutations and wild-type genes in gene clusters, etc. -- is fundamental for understanding a number of fields like ecology, evolution and genetics (and its applications extend naturally to others like finance and demography). The last few decades have made it abundantly clear that these ostensibly biological systems can be studied very fruitfully by invoking physical methods and insights, rooted in the ideas of non-equilibrium dynamics.

Much of my current work focuses on widening our current theoretical understanding of some fundamental concepts in population dynamics such as the chance of invasion of a mutant species, the mean time to extinction of a resident species, etc. We recently showed that contrary to widespread belief, the mean growth rate of a species when it is rare does not act as a reliable quantitative measure of the persistence of a species in systems with fluctuating environments. We are currently working, using analytical and numerical means, to define new metrics which do do the job and have wide applicability.

Microswimmers are microscopic bodies that can execute autonomous motion through fluids. Understanding and controlling their motion is of great significance for both biology -- with bacteria and other microbes forming ubiquitous examples of such swimmers -- and technology, with vital applications such as minuscule medical probes and lab-on-a-chip devices. Unfortunately, the heavily overdamped nature of their surroundings in practically all real fluids renders the motion of microswimmers complicated and necessitates fiendishly clever strategies of motion that Nature has evolved over millenia but human ingenuity is still grappling to comprehend.

My work in this field has mainly made use of a relatively simple design of a microswimmer -- the bead-spring model -- in order to throw light on several fundamental properties of microswimming. Using this model we have suggested a possible explanation for why bacteria sometimes swim faster in fluids of higher viscosity, and described the effects of increased smoothness and deformability of a swimmer's surface on its velocity.