Non-equilibrium FIF

red ball A simple off-equilibrium set-up involves objects at two different temperature, with a resulting heat current.

yellow ball In the QED context, there is radiative heat transfer, and associated radiation pressure.

      

yellow ball Note, that classical "blackbody" formulae break down at scales smaller than the thermal wavelength.

red ball Breaking the law, at the nanoscale (MIT news, July 29, 2009)

yellow ball "Surface Phonon Polaritons Mediated Energy Transfer between Nanoscale Gaps,"

S. Shen, A. Narayanaswamy, & G. Chen, Nano Lett. 9, 2909 (2009)

 

yellow ball Heat transfer between plates diverges at short distances due to evanescent waves (tunneling).

red ballA generalized scattering approach enables computation of Casimir forces, as well as radiation and heat transfer.

yellow ball "Nonequilibrium Electromagnetic Fluctuations: Heat Transfer and Interactions,"

M. Krüger, T. Emig, and M. Kardar, Phys. Rev. Lett. 106, 210404 (2011)

Rytov (1959):      "Fluctuational QED"

yellow ball Fluctuating currents in each object are related to its temperature by a fluctuation-dissipation condition:

yellow ball The EM field due to thermal fluctuations of one object is related to overall Green's function by:

yellow ball The overall fluctuations with many objects at different temperatures is then given by:

yellow ball From EM correlations follow the stress tensor and the Poynting vector, hence forces and radiation.

red ballResults for objects at different temperatures.

red ballSome results for moving objects.

red ball What if there is a fluid between the objects held at different temperatures?

yellow ball "Giant Casimir Effect in Fluids in Nonequilibrium Steady States,"

T. R. Kirkpatrick, J. M. Ortiz de Zárate, and J. V. Sengers, Phys. Rev. Lett. 110, 235902 (2013):

Fluctuating hydrodynamics predicts long-range correlated temperature/density fluctuations;

Pressure is locally argued to be:

Evaluating the non-equilibrium contributions to the fluctuations, they obtain a Casimir pressure

yellow ball With Yariv Kafri, we have looked at a simpler example, involving the diffusing density field between

reservoirs at different chemical potentials, i.e. in the presence of a uniform current flow.

The presence of a current leads to large, position dependent, fluctuations in density.

We local pressure variations 

Pressure fluctuations are different between plates, and outside plates, leading to a net force

The force can be attractive (hard core particles) or repulsive.

yellow ball What is the FIF between compact objects immersed in the diffusing current?

red ball Is there a FIF 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)