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Active Brownian motion with directional reversals.

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Summary
This summary is machine-generated.

Active Brownian motion in bacteria exhibits four distinct dynamical regimes based on rotational diffusion and reversal rates. These regimes show crossovers from anisotropic to isotropic behavior, with a persistence exponent emerging due to direction reversals.

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Area of Science:

  • Physics
  • Biophysics
  • Statistical Mechanics

Background:

  • Active Brownian motion is prevalent in biological systems, particularly in bacteria like Myxococcus xanthus and Pseudomonas putida.
  • This motion is characterized by intermittent direction reversals, introducing complex dynamics.

Purpose of the Study:

  • To analyze the distinct dynamical regimes of two-dimensional active Brownian motion with intermittent direction reversals.
  • To characterize these regimes by computing position distributions and persistence exponents.

Main Methods:

  • Analytical computation of position distribution.
  • Calculation of persistence exponents.
  • Exact first-passage time distribution analysis.

Main Results:

  • Identified four distinct dynamical regimes based on two timescales: rotational diffusion (D_R) and reversal rate (γ).
  • Observed a crossover from nondiffusive, anisotropic behavior to diffusive, isotropic behavior.
  • In regime II (γ⁻¹ ≪ t ≪ D_R⁻¹), the position distribution along the orthogonal direction follows a specific scaling function, and a persistence exponent α=1 emerges.

Conclusions:

  • The interplay between rotational diffusion and reversal rates creates complex, multi-regime dynamics in active Brownian motion.
  • Direction reversals are crucial in establishing specific behaviors, such as the emergence of a persistence exponent.