Sajad Aghapour (Sharif University of Technology, Tehran, and AEI)
The classical definitions of helicity, spin and orbital angular momenta of the electromagnetic field in free space have been improved in recent years in theoretical optics, stimulated by experiments with laser beams applied to studying these properties. In the course of this work, an array of quantities linked via their conservation laws has been introduced. This array, called the helicity array, is closely related to Lipkin's zilch tensor. Making use of the strong analogy between linearized gravity and Maxwell theory, one may find analogous conserved quantities, i.e. helicity, spin, and orbital angular momentum for linearized gravitational fields, which may be of interest in gravitational wave research. In this talk, I will review the results of studies in optical community and then derive the linearized gravitational analog of the helicity array.