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Department of Information Technology

TEnsor Notation for Grid Operators



  • Prof. Kurt Otto, Dept. of Information Technology, Uppsala Univ.
  • Prof. Elisabeth Larsson, Dept. of Information Technology, Uppsala Univ.


Tensors were first utilized to describe the elastic deformation of solids. Actually, the word tensor stems from the Latin word "tensus" meaning stretched. In the beginning of the 20th century, tensor calculus was refined by the Italian mathematicians Ricci and Levi-Cevita. Since then tensor calculus has been an invaluable tool in differential geometry, special and general relativity, and several branches of Physics. The classical way of using tensors is to let them define coordinate invariant linear operators.

In this project, a tensor notation is advocated from a different point of view. We consider discretizations (on structured grids) of PDE problems such that systems of linear equations arise. The coefficient matrices are typically large, complex, indefinite, and ill-conditioned. For these linear operators and the solvers (preconditioned Krylov subspace methods) for the corresponding systems, we use a tensor notation. That considerably facilitates the construction of the numerical algorithms as well as the design and implementation of our object-oriented software tools. The matrix notation, which has been long prevailing in the numerical linear algebra community, actually makes designing and coding unnecessarily complicated!



A long-term goal of these efforts were a solver of the Helmholtz Equation for Layered Media (HELM).

Updated  2022-08-31 12:39:11 by Kurt Otto.