Well-posed systems - The LTI case and beyond

Marius Tucsnak, George Weiss

Research output: Contribution to journalArticlepeer-review


This survey is an introduction to well-posed linear time-invariant (LTI) systems for non-specialists. We recall the more general concept of a system node, classical and generalized solutions of system equations, criteria for well-posedness, the subclass of regular linear systems, some of the available linear feedback theory. Motivated by physical examples, we recall the concepts of impedance passive and scattering passive systems, conservative systems and systems with a special structure that belong to these classes. We illustrate this theory by examples of systems governed by heat and wave equations. We develop local and global well-posedness results for LTI systems with nonlinear (in particular, bilinear) feedback, by extracting the abstract idea behind various proofs in the literature. We apply these abstract results to derive well-posedness results for the Burgers and Navier-Stokes equations.

Original languageEnglish
Pages (from-to)1757-1779
Number of pages23
Issue number7
StatePublished - Jul 2014


  • Burgers equation
  • Heat equation
  • Impedance passive system
  • Local well-posedness
  • Navier-Stokes equations
  • Non-linear feedback
  • Operator semigroup
  • Regular linear system
  • Scattering conservative system
  • Scattering passive system
  • Wave equation
  • Well-posed linear system


Dive into the research topics of 'Well-posed systems - The LTI case and beyond'. Together they form a unique fingerprint.

Cite this