Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-equilibrium fluctuations and nonlinear response of an active bath   We analyze the dynamics of a passive colloidal probe immersed in an active
bath using an optical trap to study three physical processes: (1) the
non-equilibrium fluctuations transferred to the probe by the active bath, (2)
the friction experienced by the probe as it is driven through the active bath,
and (3) the force relaxation of the probe returning to its equilibrium
position. We measure the local force dynamics where all of the following
characteristics are of $\mathcal{O}(1)$: the size of the probe colloid relative
to active bath particle; the size of the probe colloid relative to the
characteristic run-length of an active particle; and the timescale of probe
movement to the persistence time of an active particle. We find at P\'{e}clet
(Pe) $\ll 1$ the active suspension exhibits shear thinning down to the solvent
viscosity (but not below); at $0.85 <$ Pe $\leq 5.1$ the active bath shear
thickens; and at Pe $\geq 8.5$ the effective viscosity of the active bath shows
a decreased effect of thickening and plateaus. These results are in agreement
with recent modeling and simulations of the nonlinear rheology of an isotropic
active bath, providing experimental verification, and suggesting the model
predictions extends to moderately dense suspensions. Further, we observe that
the distribution of force fluctuations depends on Pe, unlike in passive
equilibrium baths. Lastly, we measure the energy transfer rate from the active
bath to the probe to be $\langle J \rangle \approx 10^3$ $k_B T/$s, which leads
to an increase in the effective diffusion of the probe by a factor of $\sim 2$.

28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci