Plane waves as tractor beams
Péter Forgacs (LMPT, Université de Tours, Wigner Center Budapest)
The subject of the talk is a simple but somewhat surprising effect, when an incident plane wave exerts a pulling force on the scatterer instead of the expected pushing.
This effect, which goes under the names of « tractor beam » or « negative radiation pressure », appears in a number of systems in 1 and 2 spatial dimensions. The underlying physical mechanism for the appearance of the pulling force is the sufficiently strong scattering of the incoming wave into another propagating mode in the forward direction carrying away more momentum than that contained in the incoming wave. In such a case a « surplus » of momentum is created behind the scatterer leading to the eeffect. Such a negative radiation pressure is found to appear in nonlinear field theoretical systems (kinks, vortices), also in optical (birefringent) systems, and it may also be relevant for more exotic objects like cosmic strings.
Talk based on P. Forgács, Á. Lukács, T. Romanczukiewicz, Plane waves as tractor beams, Phys. Rev. D88, 125007 (2013).