Yoshihiro Onishi | Searcharxiv

arXiv2012

Prime form and sigma function

In this article, we study some cyclic $(r,s)$ curves $X$ given by $y^r =x^s + λ_{1} x^{s-1} +...+ λ_{s-1} x + λ_s$. We give an expression for the prime form $\cE(P,Q)$, where $(P, Q \in X)$, in terms of the sigma function for some such curves, specifically any hyperelliptic curve $(r,s) = (2, 2g+1)$ as well as the cyclic trigonal curve $(r,s) = (3,4)$, $$ \cE(P,Q) =\frac{σ_{\natural_{r}}(u - v)}{\sqrt{du_1}\sqrt{d v_1}}, $$ where $\natural_r$ is a certain index of differentials. Here $u_1$ and $v_1$ are respectively the first components of $u = w(P)$ and $v = w(Q)$ which are given by the Abel map $w: X \to \CC^g$, where $g$ is the genus of $X$.

math.AG↗

arXiv2010

Universal elliptic functions

For the elliptic curve defined by the most general form $y^2 + (μ_1 x + μ_3) y = x^3 + μ_2 x^2 + μ_4 x + μ_6$, we show the power series expansion of Weierstsass sigma function $σ(u)$ at the origin is of Hurwitz integral over $\mathbb{Z}[μ_1/2, μ_2, μ_3, μ_4, μ_6]$. Namely, the coefficient $c_n$ of any term $c_n u^n/n!$ of the expansion belongs to $\mathbb{Z}[μ_1/2, μ_2, μ_3, μ_4, μ_6]$. The last section contains several first terms of $n$-plication equation of the curve.

math.NT↗

arXiv2003

On the Moduli of a quantized loop in P and KdV flows: Study of hyperelliptic curves as an extension of Euler's perspective of elastica I

Quantization needs evaluation of all of states of a quantized object rather than its stationary states with respect to its energy. In this paper, we have investigated moduli $\CMeP$ of a quantized elastica, a quantized loop with an energy functional associated with the Schwarz derivative, on a Riemann sphere $\PP$. Then it is proved that its moduli space is decomposed to a set of equivalent classes determined by flows obeying the Korteweg-de Vries (KdV) hierarchy which conserve the energy. Since the flow obeying the KdV hierarchy has a natural topology, it induces topology in the moduli space $\CMeP$. Using the topology, $\CMeP$ is classified. Studies on a loop space in the category of topological spaces $\Top$ are well-established and its cohomological properties are well-known. As the moduli space of a quantized elastica can be regarded as a loop space in the category of differential geometry $\DGeom$, we also proved an existence of a functor between a triangle category related to a loop space in {\bf Top} and that in $\DGeom$ using the induced topology. As Euler investigated the elliptic integrals and its moduli by observing a shape of classical elastica on $\CC$, this paper devotes relations between hyperelliptic curves and a quantized elastica on $\PP$ as an extension of Euler's perspective of elastica.

math.DG↗