Fluctuations of the thermal or classical component of the van der Waals force between two dielectric slabs, modeled as an ensemble of polarizable dipoles which interact via the usual electrostatic dipole-dipole interaction, are evaluated. In the model the instantaneous force is a deterministic function of the dipole configurations in the slabs, and its fluctuations are purely due to dipole fluctuations (no background thermal fluctuations of the electromagnetic field are considered). The average of the force and its variance are computed. The fluctuations of the force exhibit normal thermodynamic scaling in that they are proportional to the area of the two plates and, even more importantly, do not depend on any microscopic cutoff in the theory. The average and the variance of the thermal van der Waals forces give a unique fingerprint of these fluctuation interactions.

• Received 8 October 2012

DOI:https://doi.org/10.1103/PhysRevA.87.032111