An analysis of the spectrum of the discontinuous Galerkin method

  • Authors:
  • Lilia Krivodonova;Ruibin Qin

  • Affiliations:
  • Department of Applied Mathematics, University of Waterloo, 200 University Ave West, Waterloo, ON, N2L 3G1, Canada;Department of Applied Mathematics, University of Waterloo, 200 University Ave West, Waterloo, ON, N2L 3G1, Canada

  • Venue:
  • Applied Numerical Mathematics
  • Year:
  • 2013

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Abstract

We derive explicit expressions for the eigenvalues (spectrum) of the discontinuous Galerkin spatial discretization applied to the linear advection equation. We show that the eigenvalues are related to the subdiagonal [p/p+1] Pade approximation of exp(-z) when pth degree basis functions are used. We derive an upper bound on the eigenvalue with the largest magnitude as (p+1)(p+2). We demonstrate that this bound is not tight and prove that the asymptotic growth rate of the spectral radius is slower than quadratic in p. We also analyze the behavior of the spectrum near the imaginary axis to demonstrate that the spectral curves approach the imaginary axis although there are no purely imaginary eigenvalues.