Brownian motion

Physics

Operator (biology)

Isotropy

Mathematics

Transcription factor

Gene

Propagator

Statistical physics

Statistics

Diagonal

Mathematical analysis

Repressor

Eigenvalues and eigenvectors

Chemistry

Geometry

Quantum mechanics

Fokker–Planck equation

Differential equation

Autocorrelation

Biochemistry

Physical Review Letters

We provide an analytical solution for the time-dependent Fokker-Planck equation for a two-dimensional active Brownian particle trapped in an isotropic harmonic potential. Using the passive Brownian particle as basis states we show that the Fokker-Planck operator becomes lower diagonal, implying that the eigenvalues are unaffected by the activity. The propagator is then expressed as a combination of the equilibrium eigenstates with weights obeying exact iterative relations. We show that for the low-order correlation functions, such as the positional autocorrelation function, the recursion terminates at finite order in the Péclet number, allowing us to generate exact compact expressions and derive the velocity autocorrelation function and the time-dependent diffusion coefficient. The nonmonotonic behavior of latter quantities serves as a fingerprint of the nonequilibrium dynamics.

Analytic Solution of an Active Brownian Particle in a Harmonic Well