b.
This mathematician's principle states that solutions to Poisson's equation can be obtained by minimizing his namesake energy, a functional measure of variance. The sum over integers k from minus n to n of e to the power ikx is called his kernel and the indicator function on the rationals is sometimes named for him. He proved that for two positive coprime integers a and b, there are infinitely many primes congruent to a mod b. Specifying the values of a differential equation's solutions at the boundary is the mathematician's boundary conditions; specifying the derivatives are Von Neumann's. For 10 points, name this German mathematician who formulated the pigeonhole principle.
This mathematician's principle states that solutions to Poisson's equation can be obtained by minimizing his namesake energy, a functional measure of variance.
Johann Peter Gustav Lejeune Dirichlet