A comparison of the Almgren-Pitts and the Allen-Cahn min-max theory

Abstract: Min-max theory for the Allen-Cahn equation was developed by Guaraco and Gaspar-Guaraco. They showed that the Allen-Cahn widths are greater than or equal to the Almgren-Pitts widths. In this article we will prove that the reverse inequalities also hold i.e. the Allen-Cahn widths are less than or equal to the Almgren-Pitts widths. Hence, the Almgren-Pitts widths and the Allen-Cahn widths coincide. We will also show that all the closed minimal hypersurfaces (with optimal regularity) which are obtained from the Allen-Cahn min-max theory are also produced by the Almgren-Pitts min-max theory. As a consequence, we will point out that the index upper bound in the Almgren-Pitts setting, proved by Marques-Neves and Li, can also be obtained from the index upper bound in the Allen-Cahn setting, proved by Gaspar and Hiesmayr.