Moduli of curves with nonspecial divisors and relative moduli of $A_\infty$-structures

In this paper for each $n\ge g\ge 0$ we consider the moduli stack $\widetilde{\mathcal U}^{ns}_{g,n}$ of curves $(C,p_1,\ldots,p_n,v_1,\ldots,v_n)$ of arithmetic genus $g$ with $n$ smooth marked points $p_i$ and nonzero tangent vectors $v_i$ at them, such that the divisor $p_1+\ldots+p_n$ is nonspecial (has no $h^1$) and ample. With some mild restrictions on the characteristic we show that it is a scheme, affine over the Grassmannian $G(n-g,n)$. We also construct an isomorphism of $\widetilde{\mathcal U}^{ns}_{g,n}$ with a certain relative moduli of $A_\infty$-structures (up to an equivalence) over a family of graded associative algebras parametrized by $G(n-g,n)$.