Yau's conjecture on the first eigenvalue

In mathematics, Yau's conjecture on the first eigenvalue is, as of 2018, an unsolved conjecture proposed by Shing-Tung Yau in 1982. It asks:

Is it true that the first eigenvalue for the Laplace–Beltrami operator on an embedded minimal hypersurface of $S^{n+1}$ is $n$ ?

If true, it will imply that the area of embedded minimal hypersurfaces in $S^{3}$ will have an upper bound depending only on the genus.

Some possible reformulations are as follows:

The first eigenvalue of every closed embedded minimal hypersurface $M^{n}$ in the unit sphere $S^{n+1}$ (1) is $n$

The first eigenvalue of an embedded compact minimal hypersurface $M^{n}$ of the standard (n + 1)-sphere with sectional curvature 1 is $n$

If $S^{n+1}$ is the unit (n + 1)-sphere with its standard round metric, then the first Laplacian eigenvalue on a closed embedded minimal hypersurface ${\sum }^{n}\subset S^{n+1}$ is $n$

The Yau's conjecture is verified for several special cases, but still open in general.

Shiing-Shen Chern conjectured that a closed, minimally immersed hypersurface in $S^{n+1}$ (1), whose second fundamental form has constant length, is isoparametric. If true, it would have established the Yau's conjecture for the minimal hypersurface whose second fundamental form has constant length.

A possible generalization of the Yau's conjecture:

Let $M^{d}$ be a closed minimal submanifold in the unit sphere $S^{N+1}$ (1) with dimension $d$ of $M^{d}$ satisfying $d\geq {\frac {2}{3}}n+1$ . Is it true that the first eigenvalue of $M^{d}$ is $d$ ?