Algebraic construction of the sigma function for general Weierstrass curves

TL;DR

This paper develops an algebraic method to explicitly construct the sigma function for general Weierstrass curves, enhancing the understanding of their complex structure and associated differential forms.

Contribution

It introduces an algebraic framework for constructing the sigma function of general Weierstrass curves, including explicit formulas for holomorphic forms and the fundamental 2-form of the second kind.

Findings

Explicit algebraic expressions for holomorphic one forms.

Construction of the fundamental 2-form of the second kind.

Connection established between sigma functions and algebraic structures.

Abstract

The Weierstrass curve $X$ is a smooth algebraic curve determined by the Weierstrass canonical form, $y^r + A_{1}(x) y^{r-1} + A_{2}(x) y^{r-2} +\cdots + A_{r-1}(x) y + A_{r}(x)=0$, where $r$ is a positive integer, and each $A_j$ is a polynomial in $x$ with a certain degree. It is known that every compact Riemann surface has a Weierstrass curve $X$ which is birational to the surface. The form provides the projection $\varpi_r : X \to {\mathbb{P}}$ as a covering space. Let $R_X := {\mathbb{H}}^0(X, {\mathcal{O}}_X(*\infty))$ and $R_{\mathbb{P}} := {\mathbb{H}}^0({\mathbb{P}}, {\mathcal{O}}_{\mathbb{P}}(*\infty))$. Recently we have the explicit description of the complementary module $R_X^{\mathfrak{c}}$ of $R_{\mathbb{P}}$-module $R_X$, which leads the explicit expressions of the holomorphic one form except $\infty$, ${\mathbb{H}}^0({\mathbb{P}}, {\mathcal{A}}_{\mathbb{P}}(*\infty))$ and the trace operator $p_X$ such that $p_X(P, Q)=\delta_{P,Q}$ for $\varpi_r(P)=\varpi_r(Q)$ for $P, Q \in X\setminus\{\infty\}$. In terms of them, we express the fundamental 2-form of the second kind $\Omega$ and a connection to the sigma functions for $X$.