On regularity of the logarithmic forward map of electrical impedance tomography

Henrik Garde*, Nuutti Hyvönen, Topi Kuutela

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


This work considers properties of the logarithm of the Neumann-to-Dirichlet boundary map for the conductivity equation in a Lipschitz domain. It is shown that the mapping from the (logarithm of) the conductivity, i.e., the (logarithm of) the coefficient in the divergence term of the studied elliptic partial differential equation, to the logarithm of the Neumann-to-Dirichlet map is continuously Frechet differentiable between natural topologies. Moreover, for any essentially bounded perturbation of the conductivity, the Frechet derivative defines a bounded linear operator on the space of square integrable functions living on the domain boundary, although the logarithm of the Neumann-to-Dirichlet map itself is unbounded in that topology. In particular, it follows from the fundamental theorem of calculus that the difference between the logarithms of any two Neumannto- Dirichlet maps is always bounded on the space of square integrable functions. All aforementioned results also hold if the Neumann-to-Dirichlet boundary map is replaced by its inverse, i.e., the Dirichlet-to-Neumann map.

Original languageEnglish
JournalSIAM Journal on Mathematical Analysis
Pages (from-to)197-220
Number of pages24
Publication statusPublished - 2020
Externally publishedYes


  • Electrical impedance tomography
  • Frechet derivative
  • Functional calculus
  • Logarithm
  • Neumann-to-Dirichlet map

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