User:DVD206/On 2D Inverse Problems

On Inverse Problems in 2D

Dedicated to Nicole DeLaittre

About the book

Summary

The main object of study of this book is the relationship between local and global properties of two-dimensional manifolds (surfaces) and embedded graphs. The dimension of the unknown parameter fits the dimension of the data of the measurements in several important instances of the inverse problems. Also, two-dimensional setting has an additional structure, due to the duality between harmonic functions on embedded graphs and manifolds and the connection to special matrices. The context of the inverse problems provides a unified point of view on the work of many great mathematicians. Some of the problems simplify significantly in the graph theoretical setting, but their solutions nevertheless convey the main ideas of the solutions for their continuous analogs. These are some of the main motivations for writing this book. Even though there are references to many mathematical areas in this book, it is practically self-contained, and is intended for the use by a wide audience of people interested in the subject.

Basic definitions and background

We will start with definitions and overview of the main mathematical objects that are involved in the inverse problems of our interest. These include the domains of definitions of the functions and operators, the boundary and spectral data and interpolation/extrapolation and restriction techniques.

The inverse problems

• === Solving polynomial equation ===

Rectangular directed layered grid

• === Pascal triangle ===

Rectangular grids and gluing graphs

• === Monodromy operator ===

Ordinary differential equations (ODEs)

• === Three-term recurrence matrices and continued fractions ===

Transformations of embedded graphs

The rules for replacing conductors in series or parallel connection by a single electrically equivalent conductor follow from the equivalence of the Y-Δ or star-mesh transforms.

• Rectangular grid
  Rectangular grid

The layered case

Blaschke products

Let a_i be a set of n points in the complex unit disc. The corresponding Blaschke product is defined as

$B(z)=\prod _{k}{\frac {|a_{k}|}{a_{k}}}({\frac {a_{k}-z}{1-{\overline {a_{k}}}z}}).$

If the set of points is finite, the function defines the n-to-1 map of the unit disc onto itself,

$f:\mathbb {D} {\xrightarrow[{}]{n\leftrightarrow 1}}\mathbb {D} .$

If the set of points is infinite, the product converges and defines an automorphism of the complex unit disc, given the Blaschke condition

$\sum _{k}(1-|a_{k}|)<\infty .$

The following fact will be useful in our calculations:

$B(0)=\prod _{n}{|a_{i}|}.$

Cauchy matrices

The Cayley transform provides the link between the Stieltjes continued fractions and Blaschke products and the Pick-Nevanlinna interpolation problem at the unit disc and the half-space.

Solution of the inverse problem

Rotation invariant layered networks 

A. Elementary symmetric functions and permutations
B. Continued fractions and interlacing properties of zeros of polynomials
C. Wave-particle duality and identities involving integrals of paths in a graph and its Laplacian eigenvalues
D. Square root and finite-differences

Given the Dirichlet-to-Neumann map of a layered network, find the eigenvalues and the interpolate, calculate the Blaschke product and continued fraction. That gives the conductivities of the layeres.

The square root of the minus Laplacian

We will now consider an important special case of the inverse problem

Notation

$\mathbb {R} {\mbox{ is the set of real numbers}}$

$\mathbb {R} ^{N}{\mbox{ is the N-dimensional Euclidean space}}$

$\mathbb {C} {\mbox{ is the set of complex numbers}}$

$\mathbb {D} =\{z\in \mathbb {C} |,|z|\leq 1\}{\mbox{ is the closed unit disc}}$

$M{\mbox{ is surface}}$

$\alpha ,\beta ,\ldots {\mbox{ are analytic functions}}$

$\nabla {\mbox{ is gradient}}$

$\Delta {\mbox{ Laplace operator}}$

$\Lambda {\mbox{ is Dirichlet-to-Neumann operator}}$

$A,B,\ldots {\mbox{ are matrices}}$

$\lambda {\mbox{ is eigenvalue}}$

$\rho {\mbox{ is characteristic polynomial}}$

$P{\mbox{ is permutation matrix}}$

$F{\mbox{ is Fourier transform}}$

$\Gamma {\mbox{ is graph}}$

$G{\mbox{ is network}}$

$\gamma {\mbox{ is conductivity}}$

$q{\mbox{ is potential}}$

Acknowledgements

The author would like to thank Wiki project for the help in all stages of writing the book.

Bibliography

2. Astala, K. and P¨aiv¨arinta, L. "Calder´on’s inverse conductivity problem in the plane", http://annals.math.princeton.edu/wp-content/uploads/annals-v163-n1-p05.pdf
3. Biesel, O. D., Ingerman D. V., Morrow J. A. and Shore W. T. "Layered Networks, the Discrete Laplacian, and a Continued Fraction Identity", http://www.math.washington.edu/~reu/papers/2008/william/layered.pdf
4. Borcea, L. , Druskin, V. and Knizhnerman, L. "On the continuum limit of a discrete inverse spectral problem on optimal finite difference grids", Communications on Pure and Applied Mathematics, Vol. 000, 0001–0048 (2000)
5. Borcea, L., Druskin, V., Vasquez, G. F. and Mamonov, A. V. "Resistor network approaches to electrical impedance tomography", http://arxiv.org/abs/1107.0343
6. Cannon, J. W. "The combinatorial Riemann mapping theorem", http://www.springerlink.com/content/9w0608p039151254/
7. Curtis, E. B. and Morrow, J. A. "Inverse Problems for Electrical Networks", http://books.google.com/books/about/Inverse_Problems_for_Electrical_Networks.html?id=gLnohh95zFIC
8. Curtis, E. B., Ingerman, D. V. and Morrow, J. A. "Circular Planar Graphs and Resistor Networks", http://www.math.washington.edu/~morrow/papers/cim.pdf
9. De Verdière, Yves Colin, "Reseaux electrique planaires I", http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.224.133
10. Doyle, P. G. and Snell, L. J. "Random walks and electric networks", http://www.cse.buffalo.edu/~hungngo/classes/2005/Expanders/papers/general/randomWalk.pdf
11. Edelman, A. and Strang, G. "Pascal matrices", http://web.mit.edu/18.06/www/pascal-work.pdf
12. Fomin, S. "Loop-erased walks and total positivity", http://arxiv.org/pdf/math.CO/0004083.pdf
13. Gantmacher, F. R. and Krein, M. G. "Oscillation Matrices and Kernels and Small Vibrations of Mechanical Systems", Revised Edition, http://www.ams.org/bookstore?fn=20&arg1=diffequ&ikey=CHEL-345-H
14. Ingerman, D. V. "The Square of the Dirichlet-to-Neumann map equals minus Laplacian", http://arxiv.org/ftp/arxiv/papers/0806/0806.0653.pdf
15. Kac, M. "Can one hear the shape of a drum?", American Mathematical Monthly 73 (4, part 2): 1–23, (1966), doi:10.2307/2313748
16. Karlin, S. "Total positivity", http://books.google.com/books/about/Total_Positivity.html?id=yIarAAAAIAAJ
17. Kohn, R. and Vogelius, M. "Determining conductivity by boundary measurements", Comm. Pure Appl. Math., 37(1984), 289–298, http://onlinelibrary.wiley.com/doi/10.1002/cpa.3160370302/abstract
18. Marshall, D. E. "An elementary proof of the Pick-Nevanlinna interpolation theorem", http://projecteuclid.org/DPubS?verb=Display&version=1.0&service=UI&handle=euclid.mmj/1029001307&page=record
19. Nachman, A. I. "Global uniqueness for a two-dimensional inverse boundary value problem", http://www.jstor.org/discover/10.2307/2118653?uid=3739960&uid=2&uid=4&uid=3739256&sid=21101022816693
20. Petrushev, P. P. and Popov, A. V. "Rational approximation of real functions", 1987, http://books.google.com/books/about/Rational_Approximation_of_Real_Functions.html?id=0up9c_uo2xQC
21. Pinkus, A. "Totally positive matrices", http://www.amazon.com/Totally-Positive-Matrices-Cambridge-Mathematics/dp/0521194083
22. Sylvester, J. and Uhlmann, G. "A global uniqueness theorem for an inverse boundary value problem", Ann. of Math., 125 (1987), 153–169.
23. Uhlmann, G. "Electrical impedance tomography and Calder´on’s problem", http://www.math.washington.edu/~gunther/publications/Papers/calderoniprevised.pdf