Transient Fluctuation-Induced Force

red ball Are there long-ranged fluctuation-induced forces in active matter?

yellow ball "Fluctuation-Induced Casimir Forces in Granular Fluids,"

C. Cattuto, R. Brito, U.M.B. Marconi, F. Nori, and R. Soto, Phys. Rev. Lett. 96, 178001 (2006)

yellow ball "Nonadditivity of Fluctuation-Induced Forces in Fluidized Granular Media,"

M.R. Shaebani1, J. Sarabadani, and D.E. Wolf, Phys. Rev. Lett. 108, 198001 (2012)

yellow ball "Casimir effect in actice mtter systems,"

D. Ray, C. Reichhardt, and C.J. Olson Reichhardt, Phys. Rev. E 90, 013019 (2014)

yellow ballThe annswer is negative: no long-ranged correlations and no long-ranged interactions.

red ball Agitating active matter from rest:

yellow ball C.M. Rohwer, M. Kardar and Matthias Krüger, PRL 188, 015702 (2017)

Self-propelled colloidal particles                                                            Shaken Grains                             

red ballFluctuations of the conserved density field satisfy (model B):

Resulting in the trivial (uncorrelated) steady state

red ballWhat happens when the level of activity/noise is suddently changed (quench)?

yellow ball "Out of equilibrium behavior of Casimir-type fluctuation-induced forces for free classical fields,"

D. Dean and A. Gopinathan, Phys. Rev. E 81, 041126 (2010)

red ballDiffusive "waves" lead to transient fluctuation-induced forces between plates:

Ld

red ballTransient fluctuation-induced force between two inclusions:

red ballSimulations of ABP confirm the FIF between plates, after a different density-induced transeint:

Conserved density leads to transient long-ranged force. (How "universal" is this result?)