The “hot spots” conjecture for the Sierpinski gasket

There are many works on the “hot spots” conjecture for domains in Euclidean space since the conjecture was posed by J. Rauch in 1974. In this paper, using spectral decimation, we prove that the conjecture holds on the Sierpinski gasket, i.e., every eigenfunction of the second-smallest eigenvalue of the Neumann Laplacian (introduced by J. Kigami) attains its maximum and minimum on the boundary.