Harrell will work on the tunneling effect of quantum mechanics and on intermittency in equations such as those arising in laser physics. Other problems involve the interplay between geometry and analysis, and with attempts to understand nonlinear phenomena. Spectral theory is central to many physical problems; for example energy levels in quantum mechanics are determined as eigenvalues of certain linear operators. However, singular operators or limits lying outside the scope of well-established theories often arise in applications, and motivate much of this project. Modern physics, quantum mechanics and relativity, is a product of the twentieth century. It is founded firmly in the last century's attempt to address the microstructure of matter and to come to grips with the concepts of action-at-a distance, electro-magnetism, and heat radiation. The mathematical foundations for these developments, collectively called mathematical physics, ranges from detailed analysis of Schroedinger operators, which governs the dynamics of particles, to unified field theory, which attempts to unite the four known forces into a single theory.
