The L^2 Geometry of the Symplectomorphism Group

Doctoral Dissertation


In this thesis we study the geometry of the group of Symplectic diffeomorphisms of a closed Symplectic manifold M, equipped with the L^2 weak Riemannian metric. It is known that the group of Symplectic diffeomorphisms is geodesically complete with respect to this L^2 metric and admits an exponential mapping which is defined on the whole tangent space. Our primary objective is to describe the structure of the set of singularities of associated weak Riemannian exponential mapping, which are known as conjugate points. We construct examples of conjugate points on the Symplectomorphism group and solve the Jacobi equation explicitly along geodesics consisting of isometries of M. Using the functional calculus and spectral theory, we show that every such geodesic contains conjugate points, all of which have even multiplicity. A macroscopic view of conjugate points is then given by showing that the exponential mapping of the L^2 metric is a non-linear Fredholm map of index zero, from which we deduce that conjugate points constitute a set of first Baire category in the Symplectic diffeomorphism group. Finally, using the Fredholm properties of the exponential mapping, we give a new characterization of conjugate points along stationary geodesics in terms of the linearized geodesic equation and coadjoint orbits.


Attribute NameValues
  • etd-04152015-161300

Author James Benn
Advisor Gerard Misiolek
Contributor Gerard Misiolek, Committee Chair
Contributor Karsten Grove, Committee Member
Contributor Alex Himonas, Committee Member
Contributor Richard Hind, Committee Member
Degree Level Doctoral Dissertation
Degree Discipline Mathematics
Degree Name PhD
Defense Date
  • 2015-03-27

Submission Date 2015-04-15
  • United States of America

  • Diffeomorphism Groups

  • Hilbert Manifold

  • Euler equations

  • Symplectic Topology

  • Conjugate Points

  • University of Notre Dame

  • English

Record Visibility Public
Content License
  • All rights reserved

Departments and Units


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