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  • Open Access

Universal center-of-mass scaling shapes segment fluctuations and chromatin dynamics

Kirill E. Polovnikov1,2,* and Mehran Kardar3,†

  • *Contact author: kipolovnikov@gmail.com
  • †Contact author: kardar@mit.edu
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Phys. Rev. Research 7, 043104 – Published 27 October, 2025

DOI: https://doi.org/10.1103/ms1q-z8zp

Abstract

We show that cancellation of internal forces together with spatially uncorrelated noise generically enforces a universal 1/s scaling of the center-of-mass (COM) diffusivity for polymer segments of contour length s, independent of model details. Within an active generalized Rouse-Langevin (A-GRLE) framework for fractal polymers in a viscoelastic bath with weak activity, we derive closed-form links between segment COM motion and the short-time behavior of two-point fluctuations. The same COM law predicts transient s−3 tangent-tangent correlations along the contour following a temperature quench. Reanalyzing recent two-locus chromatin tracking, we extract a dynamic COM exponent ξ=0.77±0.16, suggesting topological constraints. These results identify model-independent signatures of collective polymer dynamics and clarify that the observed Rouse-like scaling of chromatin loci reflects transient, unentangled dynamics with an inevitable crossover to an entangled regime at longer times.

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Phys. Rev. Research 7, 043104– Published 27 October, 2025
  • Received 2 June 2025
  • Accepted 19 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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