Heat radiation from long cylindrical objects.

The heat radiated by objects smaller than or comparable in size to the thermal wavelength can be very different from the classical blackbody radiation as described by the Planck and Stefan-Boltzmann laws. We use methods based on scattering of electromagnetic waves to explore the dependence on size, shape, and material properties. In particular, we explore the radiation from a long cylinder at uniform temperature, discussing in detail the degree of polarization of the emitted radiation. If the radius of the cylinder is much smaller than the thermal wavelength, the radiation is polarized parallel to the cylindrical axis and becomes perpendicular when the radius is comparable to the thermal wavelength. For a cylinder of uniaxial material (a simple model for carbon nanontubes), we find that the influence of uniaxiality on the polarization is most pronounced if the radius is larger than a few micrometers, and quite small for the submicrometer sizes typical for nanotubes.