Research
The research interest in my group has two main directions: First, we try to understand the properties of disordered and glassy systems. Second, we apply physics principles to understand some fundamental properties of biological systems.
Theory of glassy dynamics
When the temperature of a liquid is quenched below its melting point, without allowing it to crystallize, the relaxation time increases quite rapidly by 10-12 orders of magnitude without much change in the static structure; this is known as the glass transition. The mechanism behind this dramatic slow-down remains one of the most fascinating unsolved problems of statistical physics. Apart from its fundamental importance, the problem is relevant to many other problems, such as the dynamics of many biological systems. The long-term goal is to understand the basic mechanism that leads to glassy dynamics.
Active glasses
Recent experiments have shown a remarkable similarity in the dynamics of living systems, ranging from cells and tissues to intra-cellular cytoplasm, with that of a passive glassy system. We want to understand the glassy dynamics in such systems and how it is different or similar to the equilibrium problem. The problem is quite complex and rich: we will first understand the effects of various biological properties on the glassy dynamics separately and then include them within a comprehensive theoretical framework.
Phase separation in biology
Cells organize biochemical reactions in space through the formation of different compartments or organelles. Many such compartments, such as mitochondria or lysosomes, are membrane-bound. However, there exist a number of other compartments, such as stress granules
or P granules, which are non-membrane bound and their coexistence with the continuous aqueous phase within the cell is intriguing. Recent studies show that non-membrane-bound organelles, or biomolecular condensates, are formed through phase-separation. The quantitative understanding of this process for natural bio-molecular condensates is important both for their function and control. We would like to understand how activity affects the phase separation process inside living cells.
Broad interface and FDPO
In most equilibrium phase transitions away from the transition point, the interface separating the two phases (e.g., dense/dilute or crystal/liquid) is sharp. However, there are a number of examples, where the interface can be broad and scales with system size. The phase transition in such systems can be quite rich compared to equilibrium phase transitions. Examples of such systems include sliding particles on a rough interface under gravity, the flocking transition of self-propelled particles, phase ordering in rough films, dynamics in a sand-pile etc. It is known that Porod’s law, that predicts a linear behavior of the two-point correlation function C(r/l), at small r/l where r is the distance and l being the correlation length is violated in such systems. However, the nature of the phase transition in such systems is not yet well understood. One possible mechanism to produce such broad interface is when two types of interactions compete with each other; for example, one governing the phase transition, which could be short-ranged, and the other could be activity, long-range interaction etc. We would like to understand the nature of the transition, mechanisms and implications of a broad interface in the static and dynamic properties of the system.