# MY RESEARCH

My current research is focused on understanding how structure is created in systems of active matter, liquid-like droplets in the cell, and in population growth. The backbone of my work has focused on the development of large deviation theory, which is a natural extension of statistical mechanics to out-of-equilibrium systems, to make predictions.

## Liquid Phase Separation

## Population Growth

Within the cell there are liquidlike substructures such as Cajal bodies, germ granules, and centrosomes. It is a mystery how these substructures can coexist and not mix. On the cell membrane there is a protein complex called LAT that phase separates to moderate T-cell signalling. My simulations help elucidate the physics and dynamics of this process.

## Active Matter

## Eco-evo Systems

Understanding how to predict and control population growth of populations of cells such as E. Coli can help us create general principles of nonequilibrium systems. In my latest collaboration with Ethan and Ariel at Harvard, we develop a general theory to measure population growth.

## Active Matter

In some systems, ecology and evolution are on similar time-scales which can lead to feedback of ecology on the environment and vice versa. The picture above shows our consumer-resource model in a recent preprint. Each lattice site is a specific phenotype and the dots represents the species of that phenotype.

In out-of-equilibrium systems, structure can be created by dissipating energy. This is the case for active matter. On the microscopic level each particle dissipates energy to move. Without any attraction, there is macroscopic phase separation strictly from the self propulsion. Understanding these types of processes required developing new physics in the field of large deviation theory.

Publications:

[1] GrandPre, T., Levien, E., Amir, A. (2024). Finite time corrections to the population growth rate estimator (in preparation)

[2] GrandPre, T., Teza, G., Bialek, W. (2024). Coarse graining and hidden entropy

production. (in preparation)

[3] Yu, J., Schwab, D., GrandPre, T. (2023). Noise driven phase transitions in

eco-evolutionary systems. arXiv:2310.08735

[4]Physics of Biomolecular condensates Scientific American (in Press)

[5]GrandPre, T., Zhang, Y., Pyo, A. G., Weiner, B., Li, J. L., Jonikas, M. C., & Wingreen, N. S. (2023). Effects of linker length on phase separation: lessons from the Rubisco-EPYC1 system of the algal pyrenoid. PRX Life (in press)

[6]He, G., GrandPre, T., Wilson, H., Zhang, Y., Jonikas, M. C., Wingreen, N. S., & Wang, Q. (2023). Phase-separating pyrenoid proteins from complexes in the dilute phase. Communications Biology, 6(1), 19.

[7] Sun, S., GrandPre, T., Limmer, D.T., Groves, J. (2021). Kinetic Constraints Control Membrane Localized Protein Condensation

BioRxiv preprint

[8] Omar, A., Klymko, K., GrandPre, T., Geissler, P. L., & Brady, J. F. (2021). Tuning Nonequilibrium Phase Transitions with Inertia. arXiv preprint arXiv:2108.10278.

[9] Omar, A., Klymko, K., GrandPre, T., Geissler, P.L. (2021). Phase Diagram of Active Brownian Spheres: Crystallization and the Metastability of Motility-Induced Phase Separation. Phys. Rev. Lett. 126, 188002

[10] GrandPre, T., Klymko, K., Mandadapu, K.K., Limmer, D.T. (2020). Entropy fluctuations encode collective behavior in active matter. Phys. Rev. E 103, 012613

[11] Levien, E.*, GrandPre, T.* , Amir, A. (2020). A large deviation principle linking lineage statistics to fitness. Phys. Rev. Lett. 125, 048102

[12] GrandPre, T., & Limmer, D. T. (2018). Current fluctuations of interacting active Brownian particles. Phys. Rev. E, 98(6), 060601.

*denotes first co-author

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