Fermat’s Principle and the Geometric Mechanics of Ray Optics Summer School Lectures, Fields Institute, Toronto, July 2012 Darryl D Holm Imperial College London
[email protected] http://www.ma.ic.ac.uk/~dholm/ Texts for the course include: Geometric Mechanics I: Dynamics and Symmetry, & II: Rotating, Translating and Rolling, by DD Holm, World Scientific: Imperial College Press, Singapore, Second edition (2011). ISBN 978-1-84816-195-5 and ISBN 978-1-84816-155-9. Geometric Mechanics and Symmetry: From Finite to Infinite Dimensions, by DD Holm,T Schmah and C Stoica. Oxford University Press, (2009). ISBN 978-0-19-921290-3 Introduction to Mechanics and Symmetry, by J. E. Marsden and T. S. Ratiu Texts in Applied Mathematics, Vol. 75. New York: Springer-Verlag (1994). 1 GeometricMechanicsofFermatRayOptics DDHolm FieldsInstitute,Toronto,July2012 2 Contents 1 Mathematical setting 5 2 Fermat’s principle 8 2.1 Three-dimensional eikonal equation . 10 2.2 Three-dimensional Huygens wave fronts . 17 2.3 Eikonal equation for axial ray optics . 23 2.4 The eikonal equation for mirages . 29 2.5 Paraxial optics and classical mechanics . 32 3 Lecture 2: Hamiltonian formulation of axial ray optics 34 3.1 Geometry, phase space and the ray path . 36 3.2 Legendre transformation . 39 4 Hamiltonian form of optical transmission 42 4.1 Translation-invariant media . 49 4.2 Axisymmetric, translation-invariant materials . 50 4.3 Hamiltonian optics in polar coordinates . 53 4.4 Geometric phase for Fermat’s principle . 56 4.5 Skewness . 58 4.6 Lagrange invariant: Poisson bracket relations . 63 GeometricMechanicsofFermatRayOptics DDHolm FieldsInstitute,Toronto,July2012 3 5 Axisymmetric invariant coordinates 69 6 Geometry of invariant coordinates 73 6.1 Flows of Hamiltonian vector fields .