On nonexistence of negative weight derivations on moduli algebras: Yau's conjecture

Let $A=\mathbb{F}[x_1,…,x_n]/(f_1,…,f_n)$ be a graded complete intersection Artinian algebra, where $\mathbb{F}$ is a field of characteristic zero. The grading on $A$ induces a natural grading on $\operatorname{Der}_{\mathbb{F}}(A)$. Halperin proposed a famous conjecture: $\operatorname{Der}_{\mathbb{F}}(A)_{<0}=0$, which implies the collapsing of the Serre spectral sequence for an orientable fibration with fibre an elliptic space with no cohomology in odd degrees. In the context of singularity theory the second-named author proposed the same conjecture in the special case when $f_i=\partial f/\partial x_i$ for a single polynomial $f$. H. Chen, the second-named author and Zuo [5] proved Halperin's conjecture assuming that the degrees of the $f_i$ are bounded below by a constant depending on the number $n$ of the variables and the degrees of variables. In this paper, in the special case when $f_i=\partial f/\partial x_i$ for a single polynomial $f$, we refine their result by giving a better bound, which is independent of $n$. Bibliography: 16 titles.