On Maxwell's and Poincare's Constants

We prove that for bounded and convex domains in three dimensions, the Maxwell constants are bounded from below and above by Friedrichs' and Poincar\'e's constants. In other words, the second Maxwell eigenvalues lie between the square roots of the second Neumann-Laplace and the first Dirichlet-Laplace eigenvalue.Comment: Key Words: Maxwell's equations, Maxwell constant, second Maxwell eigenvalue, electro statics, magneto statics, Poincare's inequality, Friedrichs' inequality, Poincare's constant, Friedrichs' constan