Many-body theory; quantum Hall effect, Closed and approximate solutions to the Schrödinger, Dirac, Klein-Gordon and other equations of quantum mechanics, General topics in linear spectral theory for PDEs, PDEs in connection with relativity and gravitational theory, Relativistic quantum mechanics, Dirac operator, eigenvalues, variational methods, indefinite integrals, nonlinear eigenvalue problems, nonlinear elliptic equations, min-max., Nonlinear eigenvalue problems and nonlinear spectral theory for PDEs, Variational principles of physics, Nonlinear elliptic equations, Variational methods for eigenvalues of operators, Atomic physics