On 2D Inverse Problems/Fourier coordinates
Let be a not unit N'th root of unity .
We consider the following discrete Fourier transform given by the symmetric Vandermonde matrix:
The square of the Fourier transform is the identity transform:
Exercise (*). If a network w/conductivity is rotation invariant then its Dirichlet-to-Neumann map is diagonal in the discrete Fourier coordinates. (Hint) The conductivity equation is rotation invariant.