The Zilch Vortical Effect

Understand

We study the question if a helicity transporting current is generated in a rotating photon gas at finite temperature.

• One problem is that there is no gauge invariant local notion of helicity or helicity current.
• We circumvent this by studying not only the optical helicity current but also the gauge-invariant "zilch" current.
• In order to avoid problems of causality, we quantize the system on a cylinder of a finite radius and then discuss the limit of infinite radius.