arXiv subjects

Shigeki Matsutani

Publications and source records attributed to Shigeki Matsutani.

At least 19 recordsLinked to original sources

arXiv2026

Geometric, algebraic and analytic properties of hyperelliptic $\mathrm{al}_{ab}$ function of genus $g$

In this paper, we investigate the geometric, algebraic and analytic properties of the hyperelliptic $\mathrm{al}_{ab}$ functions of a hyperelliptic curve $X$ with genus $g$ as the $\mathrm{al}_{ab}$ functions together with the $\mathrm{al}_a$ functions are a generalization of the Jacobi elliptic $\mathrm{sn}$, $\mathrm{cn}$, and $\mathrm{dn}$ functions. We then demonstrate the differential identities of the $\mathrm{al}_{ab}$ function. These identities are the novel integrable partial nonlinear differential equations as a natural extension of the hyperelliptic solutions of the modified Korteweg-de Vries equation in terms of the $\mathrm{al}_a$ function. Thus, we also show that by the identities, the $\mathrm{al}_{ab}$ function has the capability to be the hyperelliptic solution to the nonlinear Schrödinger and complex modified Korteweg-de Vries equations.

nlin.SI↗

arXiv2026

Closed real plane curves of hyperelliptic solutions of focusing gauged modified KdV equation of genus $g$

The real part of the focusing modified Korteweg-de Vries (MKdV) equation defined over the complex field $\mathbb{C}$ is reduced to the focusing gauged MKdV (FGMKdV) equation. In this paper, we construct the real hyperelliptic solutions of FGMKdV equation in terms of data of the hyperelliptic curves of genus $g$ and demonstrate the closed hyperelliptic plane curves of genus $g=5$ whose curvature obeys the FGMKdV equation by extending the previous results of genus three (Matsutani, {\it{J. Geom. Phys}} {\bf{215}} (2025) 105540). These are a generalization of Euler's elasticae.

nlin.SI↗

arXiv2025

Visualization of curvature on curve and surface by tangential angle parametrization

We propose a unified method to visualize curvature on planar curves and surfaces of revolution using the tangential angle parameter. For plane curves, placing markers at equal increments of the tangential angle reveals local bending features and naturally highlights inflection points and vertices. This approach extends to surfaces of revolution, where curvature lines drawn at equal tangential angle steps reflect principal curvature variations and naturally expose ridge and parabolic curves. Our method provides clear, consistent visualizations without arbitrary parameter tuning, offering geometric insight for both analysis and design applications.

math.DG↗

arXiv2025

Closed real plane curves of hyperelliptic solutions of focusing gauged modified KdV equation of genus three

The real and imaginary parts of the focusing modified Korteweg-de Vries (MKdV) equation defined over the complex field $\mathbb{C}$ give rise to the focusing gauged MKdV (FGMKdV) equations. As a generalization of Euler's elastica whose curvature obeys the focusing static MKdV (FSMKdV) equation, we study real plane curves whose curvature obeys the FGMKdV equation since the FSMKdV equation is a special case of the FGMKdV equation. In this paper, we focus on the hyperelliptic curves of genus three. By tuning some moduli parameters and initial conditions, we show closed real plane curves associated with the FGMKdV equation beyond Euler's figure-eight of elastica.

nlin.SI↗

arXiv2025

Euler's original derivation of elastica equation

Euler derived the differential equations of elastica by the variational method in 1744, but his original derivation has never been properly interpreted or explained in terms of modern mathematics. We elaborate Euler's original derivation of elastica and show that Euler used Noether's theorem concerning the translational symmetry of elastica, although Noether published her theorem in 1918. It is also shown that his equation is essentially the static modified KdV equation which is obtained by the isometric and isoenergy conditions, known as the Goldstein-Petrich scheme.

math-ph↗

arXiv2024

On real hyperelliptic solutions of focusing modified KdV equation

We study the real hyperelliptic solutions of the focusing modified KdV (MKdV) equation of the genus three. Since the complex hyperelliptic solutions of the focusing MKdV equation over $\mathbb{C}$ are associated with the real gauged MKdV equation, we present a novel construction of the real hyperelliptic solutions of the gauged MKdV equation. When the gauge field is constant, it can be regarded as the real solution of the focusing MKdV equation, and thus we also discuss the behavior of the gauge field numerically.

math-ph↗

arXiv2024

Nonlinear Schrödinger equation in terms of elliptic and hyperelliptic $σ$ functions

It is known that the elliptic function solutions of the nonlinear Schrödinger equation are reduced to the algebraic differential relation in terms of the Weierstrass sigma function, $\displaystyle{ \left[-{\frak{i}}\frac{\partial}{\partial t} +α\frac{\partial}{\partial u}\right]Ψ-\frac{1}{2} \frac{\partial^2}{\partial u^2}Ψ+(Ψ^* Ψ) Ψ= \frac12 (2β+α^2-3\wp(v))Ψ}$, where $Ψ(u;v, t):=\mathrm{e}^{αu+{\frak{i}}βt+c}$ $\displaystyle{\frac{\mathrm{e}^{-ζ(v)u}σ(u+v)}{σ(u)σ(v)}}$, its dual $Ψ^*(u; v,t)$, and certain complex numbers $α, β$ and $c$. In this paper, we generalize the algebraic differential relation to those of genera two and three in terms of the hyperelliptic sigma functions.

nlin.SI↗

arXiv2024

Conway's law, revised from a mathematical viewpoint

In this article, we revise Conway's Law from a mathematical point of view. By introducing a task graph, we first rigorously state Conway's Law based on the homomorphisms in graph theory for the software system and the organizations that created it. Though Conway did not mention it, the task graph shows the geometric structure of tasks, which plays a crucial role. Furthermore, due to recent requirements for high-level treatment of communication (due to security, knowledge hiding, etc.) in organizations and hierarchical treatment of organizations, we have reformulated these statements in terms of weakened homomorphisms, and the continuous maps in graph topology. In order to use graph topology and the continuous map in Conway's law, we have prepared them as mathematical tools, and then we show the natural expression of Conway's correspondences with hierarchical structures.

cs.SE↗

arXiv2024

Statistical mechanics of elastica for the shape of supercoiled DNA: hyperelliptic elastica of genus three

This article studies the statistical mechanics of elastica as a model of the shapes of the supercoiled DNA, and shows that its excited states can be characterized by the focusing modified KdV (MKdV) equation due to thermal fluctuation. Following the previous paper (Matsutani and Previato, Physica D 430 (2022) 133073), the hyperelliptic solutions of the focusing modified KdV (MKdV) equation of genus three are considered. There appears a pattern as a repetition of the modulation of figure-eight and the inverse 'S' as a thermal fluctuation of elastica, called the S-eight mode. Our model states that the excited states of elastica due to the thermal effect have the S-eight mode, which reproduces the shapes of the AFM image of the supercoiled DNAs observed by Japaridze et al. (Nano Lett. 17 3, (2017) 1938).

cond-mat.soft↗

arXiv2023

A graphical representation of hyperelliptic KdV solutions

The periodic and quasi-periodic solutions of the integrable system have been studied for four decades based on the Riemann theta functions. However, there is a fundamental difficulty in representing the solutions graphically because the Riemann theta function requires several transcendental parameters. This paper presents a novel method for the graphical representation of such solutions from the algebraic treatment of the periodic and quasi-periodic solutions of the Baker-Weierstrass hyperelliptic $\wp$ functions. We demonstrate the graphical representation of the hyperelliptic $\wp$ functions of genus two.

nlin.SI↗

arXiv2023

A novel symmetry in nanocarbons: pre-constant discrete principal curvature structure

Since the first-principles calculations in quantum chemistry precisely provide possible configurations of carbon atoms in nanocarbons, we have analyzed the geometrical structure of the possible carbon configurations and found that there exists a novel symmetry in the nanocarbons, i.e., the pre-constant discrete principal curvature (pCDPC) structure. In terms of the discrete principal curvature based on the discrete geometry for trivalent oriented graphs developed by Kotani, Naito, and Omori (Comput. Aided Geom. Design, $\bf{58}$, (2017), 24-54), we numerically investigated discrete principal curvature distribution of the nanocarbons, C$_{60}$, carbon nanotubes, C$_{120}$ (C$_{60}$ dimer), and C$_{60}$-polymers (peanut-shaped fullerene polymers). While the C$_{60}$ and nanotubes have the constant discrete principal curvature (CDPC) as we expected, it is interesting to note that the C$_{60}$-polymers and C$_{60}$ dimer also have the almost constant discrete principal curvature, i.e., pCDPC, which is surprising. A nontrivial pCDPC structure with revolutionary symmetry is available due to discreteness, though it has been overlooked in geometry. In discrete geometry, there appears a center axisoid which is the discrete analogue of the center axis in the continuum differential geometry but has three-dimensional structure rather than a one-dimensional curve due to its discrete nature. We demonstrated that such pCDPC structure exists in nature, namely in the C$_{60}$-polymers. Furthermore, since we found that there is a positive correlation between the degree of the CDPC structure and stability of the configurations for certain class of the C$_{60}$-polymers, we also revealed the origin of the pCDPC structure from an aspect of materials science.

cond-mat.mtrl-sci↗

arXiv2023

Algebraic construction of the sigma function for general Weierstrass curves

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 $p_X(P, Q)=δ_{P,Q}$ 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 $Ω$ and a connection to the sigma functions for $X$.

math.AG↗

arXiv2023

Complementary Modules of Weierstrass Canonical Forms

The Weierstrass curve is a pointed curve $(X,\infty)$ with a numerical semigroup $H_X$, which is a normalization of the curve given by the Weierstrass canonical form, $y^r + A_{1}(x) y^{r-1} + A_{2}(x) y^{r-2} +\dots + A_{r-1}(x) y + A_{r}(x)=0$ where each $A_j$ is a polynomial in $x$ of degree $\leq j s/r$ for certain coprime positive integers $r$ and $s$, $r$<$s$, such that the generators of the Weierstrass non-gap sequence $H_X$ at $\infty$ include $r$ and $s$. The Weierstrass curve has the projection $\varpi_r\colon X \to {\mathbb P}$, $(x,y)\mapsto x$, as a covering space. Let $R_X := {\mathbf H}^0(X, {\mathcal O}_X(*\infty))$ and $R_{\mathbb P} := {\mathbf H}^0({\mathbb P}, {\mathcal O}_{\mathbb P}(*\infty))$ whose affine part is ${\mathbb C}[x]$. In this paper, for every Weierstrass curve $X$, we show the explicit expression of the complementary module $R_X^{\mathfrak c}$ of $R_{\mathbb P}$-module $R_X$ as an extension of the expression of the plane Weierstrass curves by Kunz. The extension naturally leads the explicit expressions of the holomorphic one form except $\infty$, ${\mathbf H}^0({\mathbb P}, {\mathcal A}_{\mathbb P}(*\infty))$ in terms of $R_X$. Since for every compact Riemann surface, we find a Weierstrass curve that is bi-rational to the surface, we also comment that the explicit expression of $R_X^{\mathfrak c}$ naturally leads the algebraic construction of generalized Weierstrass' sigma functions for every compact Riemann surface and is also connected with the data on how the Riemann surface is embedded into the universal Grassmannian manifolds.

math.AG↗

arXiv2022

The sigma function over a family of cyclic trigonal curves with a singular fiber

In this paper we investigate the behavior of the sigma function over the family of cyclic trigonal curves $X_s$ defined by the equation $y^3 =x(x-s)(x-b_1)(x-b_2)$ in the affine $(x,y)$ plane, for $s\in D_\varepsilon:=\{s \in \mathbb{C} | |s|<\varepsilon\}$. We compare the sigma function over the punctured disc $D_\varepsilon^*:=D_\varepsilon\setminus\{0\}$ with the extension over $s=0$ that specializes to the sigma function of the normalization $X_{\hat{0}}$ of the singular curve $X_{s=0}$ by investigating explicitly the behavior of a basis of the first algebraic de Rham cohomology group and its period integrals. We demonstrate, using modular properties, that sigma, unlike the theta function, has a limit. In particular, we obtain the limit of the theta characteristics and an explicit description of the theta divisor translated by the Riemann constant.

math.AG↗

arXiv2021

An algebro-geometric model for the shape of supercoiled DNA

This article proposes a model including thermal effects for closed supercoiled DNA. Existing models include an elastic rod. Euler's elastica, ideal elastic rods on a plane, have only two kinds of closed shapes, the circle and a figure-eight, realized as minima of the Euler-Bernoulli energy. Even considering three dimensional effects, this elastica model provides much simpler shapes than observed via Atomic-Force Microscope (AFM), since the minimal points of the energy are expressed by elliptic functions. In this paper, by a generalization of elastica, we obtain shapes determined by data of hyperelliptic curves, which partially reproduce the shapes and properties of the DNA.

cond-mat.soft↗

arXiv2020

A Novel Discrete Theory of a Screw Dislocation in the BCC Crystal Lattice

In this paper, we proposed a novel method using the elementary number theory to investigate the discrete nature of the screw dislocations in crystal lattices, simple cubic (SC) lattice and body centered cubic (BCC) lattice, by developing the algebraic description of the dislocations in the previous report (Hamada, Matsutani, Nakagawa, Saeki, Uesaka, Pacific J. Math.~for Industry {\bf{10}} (2018), 3). Using the method, we showed that the stress energy of the screw dislocations in the BCC lattice and the SC lattice are naturally described; the energy of the BCC lattice was expressed by the truncated Epstein-Hurwitz zeta function of the Eisenstein integers, whereas that of SC lattice is associated with the truncated Epstein-Hurwitz zeta function of the Gauss integers.

math-ph↗

arXiv2020

Trigonal Toda lattice Equation

In this article, we give the trigonal Toda lattice equation, $$ -\frac{1}{2}\frac{d^3}{d t^3} q_{\ell}(t) = e^{q_{\ell+1}(t)} +e^{q_{\ell+ζ_3}(t)} +e^{q_{\ell+ζ_3^2}(t)}-3e^{q_\ell(t)}, $$ for a lattice point $\ell \in \mathbb{Z}[ζ_3]$ as a directed 6-regular graph where $ζ_3=e^{2πi/3}$, and its elliptic solution for the curve $y(y-s)=x^3$, ($s\neq 0$).

nlin.SI↗

arXiv2019

On $Λ$-Elastica

In this paper, we investigate a transition from an elastica to a piece-wised elastica whose connected point defines the hinge angle $ϕ_0$; we refer the piece-wised elastica $Λ_{ϕ_0}$-elastica or $Λ$-elastica. The transition appears in the bending beam experiment; we compress elastic beams gradually and then suddenly due the rupture, the shapes of $Λ$-elastica appear. We construct a mathematical theory to describe the phenomena and represent the $Λ$-elastica in terms of the elliptic $ζ$-function completely. Using the mathematical theory, we discuss the experimental results from an energetic viewpoint and numerically show the explicit shape of $Λ$-elastica. It means that this paper provides a novel investigation on elastica theory with rupture.

physics.class-ph↗