We present a new, short proof of the increased regularity obtained by
solutions to uniformly parabolic partial differential equations. Though this
setting is fairly introductory, our new method of proof, which uses a priori
estimates, can be extended to prove analogous results for problems with
time-dependent coefficients, transport equations, and nonlinear equations even
when other tools, such as semigroup methods or the use of explicit fundamental
solutions, are unavailable.Comment: 8 page