Mechanical and Civil Engineering Seminar

Near field force and energy exchange between two objects due to electrodynamic fluctuations give rise to dispersion forces such as Casimir and van der Waals (vdW) forces, and thermal radiative transfer exceeding Planck s theory of blackbody radiation. The two phenomena dispersion forces and near-field enhancement of thermal radiation have common origins in the electromagnetic fluctuations. The forces are manifested through the Maxwell stress tensor of the electromagnetic field and radiative transfer through the Poynting vector. Both phenomena are elegantly described in terms of the dyadic Green s function (DGF) of the vector Helmholtz equation that governs the electromagnetic fields. In this talk, I will focus on recent results regarding the effect of surface curvature on the near-field radiative transfer due to surface polaritons. In particular, I will discuss a new proximity approximation we have proposed that can be used to predict heat transfer in regimes where computation becomes prohibitive. van der Waals forces play a significant role in the interactions between macroscopic objects at micrometer and nanometer length scales. Lifshitz, in his seminal work outlined a method for computing the vdW forces between two semi--infinite regions separated by a vacuum gap. The generalization of Lifshitz's method to calculating vdW forces between semi-infinite regions separated by dissipative media is not straightforward because of the difficulty in defining an electromagnetic stress tensor in dissipative media. An approach proposed by Dzyaloshinskii, Lifshitz, and Pitaevskii, shrouded in the complicated language of quantum field theory, is the most frequently used generalization of Lifshitz's method to calculate forces between objects separated by absorbing media. Using the properties of the DGF, I will present a new solution to a long-standing problem in the field of dispersion forces that of vdW/Casimir forces in dissipative media.