Date : January 8, 2026
Venue : Asan Science Building Room 524, Korea University, Seoul.
Inquiry : Email to Seong-Deog Yang at sdyang(at)korea.ac.kr.
Time : 2026/1/8/ 1:30~2:00
Registration
Time : 2026/1/8 2:00-2:40
Speaker : Sakuma Takeshita (Tokushima University)
Title : Discrete minimal Darboux transformations
Abstract :
Corro, Ferreira, and Tenenblat illustrated minimal surfaces in the Euclidean space related by
Darboux transformations. A pair of minimal surfaces related by Darboux transformations is
called a minimal Darboux pair, and a superposition principle for minimal Darboux pairs was
further demonstrated. Subsequently, Martínez, Roitman, and Tenenblat showed that the
corresponding Gauss maps satisfy a Riccati-type differential equation, and Hertrich-Jeromin
and Honda simplified this proof by employing the Bianchi permutability of transformations
for isothermic surfaces.
In this talk, using a quaternionic calculus, we introduce the permutability of Christoffel, Goursat,
and Darboux transformations for discrete isothermic surfaces in the Euclidean space. As an
application, it is shown that the corresponding discrete Gauss maps of a discrete minimal
Darboux pair satisfy a Riccati-type difference equation. Furthermore, by applying the
higher-dimensional permutability, we obtain a superposition principle for discrete minimal
Darboux pairs. This is based on ongoing project with Masashi Yasumoto.
Time : 2026/1/8 3:00-3:40
Speaker : Naoya Suda (Kobe University)
Title : Discrete spacelike K-nets in Minkowski 3-space
Abstract : Sauer and Wunderlich introduced a discrete analogue of asymptotic Chebyshev coordinates
for surfaces of constant negative Gaussian curvature in Euclidean space. Bobenko and Pinkall
investigated the corresponding Lax pairs and proved that the discrete sine-Gordon equation
arises as the compatibility condition.
In this talk, we present results on a discrete analogue of asymptotic Chebyshev coordinates
for spacelike surfaces of constant negative (extrinsic) Gaussian curvature in Minkowski space,
together with the associated Lax pairs. We begin by reviewing the Lax pairs studied by Bobenko
and Pinkall and their compatibility condition, and then explain how the situation differs in
the Minkowski setting. We also discuss Bäcklund transformations, a classical method for producing
new surfaces of constant negative Gaussian curvature from a given one. In the discrete case,
Bäcklund transformations can likewise be formulated, and in particular, we describe an approach to
Bäcklund transformations based on gauge transformations of the Lax pairs.
Time : 2026/1/8 4:00-4:40
Speaker : Jooho Lee (KIAS)
Title : TBA
Abstract : TBA
Time : 2026/1/8 5:00-5:40
Speaker : Wonjoo Lee (Korea University)
Title : TBA
Abstract : TBA
Organizing Committee: Joseph Cho (Handong Global University), Wonjoo Lee (Korea University), Seong-Deog Yang (Korea University, Chair)
Partially supported by NRF of Korea funded by MSIT (Korea-Austria Scientific and Technological Cooperation RS-2025-1435299)