Fig. 3.

(A–C) Simulations of a passive chain (Top) and active chains with contractile (Middle) and extensile (Bottom) dipoles, with N = 5,000 and $R_s/a=8$. In the active cases, $A=2$, $k_{\mathrm{o}\mathrm{n}}=10$, and $k_{\mathrm{o}\mathrm{ff}}=50$. Also see SI Appendix, Movies S4–S7. (A) Fiber configurations at different times with red segments showing instantaneous dipole locations. (B) The nematic structure of the fiber in a shell of thickness $a$ on the surface of the confining sphere. Colors show the maximum eigenvalue ${\lambda }_Q^{\mathrm{m}\mathrm{a}\mathrm{x}}$ of the nematic order tensor $\mathbf{Q}\left(\mathbf{r}\right)=⟨\mathbf{n}\mathbf{n}-\mathbf{I}/3⟩$ (i.e., the scalar order parameter), and black segments show the corresponding nematic director. (C) Chromatin displacement maps calculated in a plane across the spherical domain over a time interval $\mathrm{\Delta }t=0.2$. Arrows are color-coded according to the direction of displacement. (D) Average spatial autocorrelation functions of the displacement maps for increasing values of the displacement time $\mathrm{\Delta }t$. (E) Growth rate $\beta$ of the order parameter $⟨{\lambda }_Q^{\mathrm{m}\mathrm{a}\mathrm{x}}⟩$ as a function of activity for different combinations of $k_{\mathrm{o}\mathrm{n}}$ and $k_{\mathrm{o}\mathrm{ff}}$. The growth rate is calculated during the initial exponential increase of $⟨{\lambda }_Q^{\mathrm{m}\mathrm{a}\mathrm{x}}⟩$, which we average over spherical regions of size $0.5R_s$ (E, Inset).