Study of Mpemba Effect in Active System

Pal, Aritra (2025) Study of Mpemba Effect in Active System. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Aritra Pal (20MS003)) 20MS003_Thesis_file.pdf Restricted to Repository staff only Download (2MB)

Abstract

The Mpemba effect, where a system initially at a higher temperature can relax faster than a colder one, has as long challenged our understanding of thermal processes. In this thesis, we explore its manifestation in non-equilibrium active systems, focusing on variants of the Vicsek model that exhibit collective motion through local alignment under noise. By simulating quench dynamics from disordered initial conditions at varying noise levels to a fixed low-noise state, we systematically investigated relaxation behavior across different densities, interaction radii, and particle speeds. We quantify ordering through time-evolving order parameters and spatial correlation functions. Our results reveal that systems initialized at higher noise, despite being more disordered, often cluster more efficiently, facilitating faster alignment and ordering—an emergent signature of the Mpemba effect in active matter. The study demonstrates a clear coupling between density fluctuations and velocity alignment, offering a novel perspective on memory effects and anomalous relaxation in driven systems.

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