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Author: Joshua W Burby
Requested Type: Poster
Submitted: 2016-02-14 14:45:18


Contact Info:
Courant Institute of Mathematical Sciences
251 Mercer St
New York, New York   10012

Abstract Text:
I will argue that high-order variational drift kinetic theories contain unphysical rapidly varying modes that are not seen at low-orders. These unphysical modes, which may be rapidly oscillating, damped, or growing, are ushered in by a failure of conventional high-order drift kinetic theory to preserve the structure of its parent model's initial value problem (Vlasov-Poisson for electrostatics, Vlasov-Darwin or Vlasov-Maxwell for electromagnetics.) In short, the system phase space is unphysically enlarged in high-order variational drift kinetic theory. I will then present an alternative, ``renormalized" variational approach to drift kinetic theory that manifestly respects the parent model's initial value problem. The basic philosophy underlying this alternate approach is that high-order drift kinetic theory ought to be derived by truncating the all-orders system phase space Lagrangian instead of the usual ``field+particle" Lagrangian. For the sake of clarity, this story will be told mainly through the lense of a finite-dimensional toy model of high-order variational drift kinetics; the analogous full-on drift kinetic results will be summarized briefly.