Velocity Distribution and Diffusion of an Athermal Inertial Run-and-Tumble Particle in a Shear-Thickening Medium
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| Format: | Preprint |
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2025
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| author | Howlader, Subhanker Mondal, Sayantan Das, Prasenjit |
| author_facet | Howlader, Subhanker Mondal, Sayantan Das, Prasenjit |
| contents | We study the dynamics of an athermal inertial run-and-tumble particle moving in a shear-thickening medium in $d=1$. The viscosity of the medium is represented by a nonlinear function $f(v)\sim\tan(v)$, while a symmetric dichotomous noise of strength $Σ$ and flipping rate $λ$ models the activity of the particle. Starting from the Fokker-Planck~(FP) equation for the time-dependent probability distribution $W_{\pmΣ}(v, t)$ of the particle's velocity $v$ at time $t$ and the active force is $\pmΣ$, we analytically derive the steady-state velocity distribution function $W_s(v)$ and a quadrature expression for the effective diffusion coefficient $D_{\rm eff}$. For a fixed $Σ$, $W_s(v)$ undergoes multiple transitions with varying $λ$, and we have identified the corresponding transition points. We then numerically compute $W_s(v)$, the mean-squared velocity $\langle v^2\rangle(t)$, and the diffusion coefficient $D_{\rm eff}$, all of which show excellent agreement with the analytical results in the steady-state. Finally, we test the robustness of the transitions in $W_s(v)$ by considering an alternative $f(v)$ function that also capture the shear-thickening behavior of the medium. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_12313 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Velocity Distribution and Diffusion of an Athermal Inertial Run-and-Tumble Particle in a Shear-Thickening Medium Howlader, Subhanker Mondal, Sayantan Das, Prasenjit Statistical Mechanics Soft Condensed Matter Mathematical Physics Chemical Physics We study the dynamics of an athermal inertial run-and-tumble particle moving in a shear-thickening medium in $d=1$. The viscosity of the medium is represented by a nonlinear function $f(v)\sim\tan(v)$, while a symmetric dichotomous noise of strength $Σ$ and flipping rate $λ$ models the activity of the particle. Starting from the Fokker-Planck~(FP) equation for the time-dependent probability distribution $W_{\pmΣ}(v, t)$ of the particle's velocity $v$ at time $t$ and the active force is $\pmΣ$, we analytically derive the steady-state velocity distribution function $W_s(v)$ and a quadrature expression for the effective diffusion coefficient $D_{\rm eff}$. For a fixed $Σ$, $W_s(v)$ undergoes multiple transitions with varying $λ$, and we have identified the corresponding transition points. We then numerically compute $W_s(v)$, the mean-squared velocity $\langle v^2\rangle(t)$, and the diffusion coefficient $D_{\rm eff}$, all of which show excellent agreement with the analytical results in the steady-state. Finally, we test the robustness of the transitions in $W_s(v)$ by considering an alternative $f(v)$ function that also capture the shear-thickening behavior of the medium. |
| title | Velocity Distribution and Diffusion of an Athermal Inertial Run-and-Tumble Particle in a Shear-Thickening Medium |
| topic | Statistical Mechanics Soft Condensed Matter Mathematical Physics Chemical Physics |
| url | https://arxiv.org/abs/2507.12313 |