@TechReport{	  it:2012-008,
  author	= {Kenneth Duru and Gunilla Kreiss},
  title		= {Numerical Interaction of Boundary Waves with Perfectly
		  Matched Layers in Elastic Waveguides},
  institution	= {Department of Information Technology, Uppsala University},
  department	= {Division of Scientific Computing},
  year		= {2012},
  number	= {2012-008},
  month		= apr,
  abstract	= {Perfectly matched layers (PML) are a novel technique to
		  simulate the absorption of waves in open domains. Wave
		  propagation in isotropic elastic waveguides has the
		  possibility to support propagating modes with negative
		  group velocities and long wavelengths. Propagating modes
		  with negative group velocities can lead to temporally
		  growing solutions in the PML. In this paper, we demonstrate
		  that negative group velocities in isotropic elastic
		  waveguides are not harmful to the discrete PML. Analysis
		  and numerical experiments confirm the accuracy and the
		  stability of the PML.}
}