Heidelberg 2015 – wissenschaftliches Programm

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SYTL: Symposium Interactions between Twisted Light and Particles

SYTL 1: Symposium on interactions between twisted light and particles I (SYTL)

SYTL 1.1: Hauptvortrag

Freitag, 27. März 2015, 11:00–11:30, C/gHS

Optical curl forces and beyond — •Michael Berry — H H Wills Physics Laboratory, University of Bristol, UK

A physical example of a force that depends on position but is not derivable from a potential, that is, a nonconservative force with non-zero curl, is the force on a dielectric particle in an optical field. The resulting dynamics need not be Hamiltonian or Lagrangian, yet is non-dissipative. Noether’s theorem does not apply, so the link between symmetries and conservation laws is broken. The physical existence of curl forces has been controversial and the subject of intense debate among engineers. Motion under curl forces near optical vortices can be understood in detail, and the full series of ‘superadiabatic’ correction forces derived, leading to an exact slow manifold in which fast (internal) and slow (external) motion of the particle is separated.