11. Getoor's research deals with probability theory, especially the theory of Markov processes and potential theory . 12. Modern potential theory is also intimately connected with probability and the theory of Markov chains. 13. In potential theory , Frostman's lemma is named after him. 14. The potential theory underwent many refinements and changes throughout the years since its first report. 15. Beyond this book, Doob is best known for his work on martingales and probabilistic potential theory . 16. This generalization is associated with the potential theory of simple layer potentials on " S ". 17. Elliptic operators are typical of potential theory , and they appear frequently in electrostatics and continuum mechanics. 18. See Cartan's lemma ( potential theory ). 19. These definitions reflect a relationship between martingale theory and potential theory , which is the study of harmonic functions. 20. In the case of an incompressible flow the velocity potential satisfies Laplace's equation, and potential theory is applicable.