# A First-Order Dynamical Transition in the displacement distribution of a Driven Run-and-Tumble Particle

## TL;DR

This paper analyzes the displacement distribution of a driven run-and-tumble particle, revealing a first-order dynamical phase transition characterized by nonanalytic behavior in large deviation functions.

## Contribution

It uncovers a novel first-order dynamical phase transition in the displacement distribution of a driven run-and-tumble particle, supported by analytical and numerical evidence.

## Key findings

- Displacement distribution exhibits non-Gaussian large deviations.
- A first-order phase transition occurs at a critical displacement value.
- Numerical simulations confirm analytical predictions.

## Abstract

We study the probability distribution $P(X_N=X,N)$ of the total displacement $X_N$ of an $N$-step run and tumble particle on a line, in presence of a constant nonzero drive $E$. While the central limit theorem predicts a standard Gaussian form for $P(X,N)$ near its peak, we show that for large positive and negative $X$, the distribution exhibits anomalous large deviation forms. For large positive $X$, the associated rate function is nonanalytic at a critical value of the scaled distance from the peak where its first derivative is discontinuous. This signals a first-order dynamical phase transition from a homogeneous `fluid' phase to a `condensed' phase that is dominated by a single large run. A similar first-order transition occurs for negative large fluctuations as well. Numerical simulations are in excellent agreement with our analytical predictions.