This seminar aims to have reserach exchanges among the reseachers of the
differential geometry,the geometric analysis, topology, algebraic geometry
and its applications.
(This seminar is held as an event of RIST TUS ``Division of Joint Research
of Geometry and Natural Science''.)
2026
・The 1st TUS Geometry & Natural Science
Speaker: Akiyuki Takahashi（Tokyo University of Science）
Title: Discrete dislocation dynamics modeling of dislocation-precipitate interactions
: Application to numerical simulation of size effects in materials
Date: July 8, 2026, 17:00-18:00
Place: Tokyo University of Science, Kagurazaka Campus
(344 room, 4nd floor, Building No. 3)
Abstract: Discrete Dislocation Dynamics (DDD) is an effective numerical analysis method for plastic deformation based on the microscopic motion of dislocations in materials. In widely used engineering alloys, precipitation hardening, where precipitates act as obstacles to dislocation motion, is a representative strengthening mechanism. To quantitatively understand the mechanism of precipitation hardening, it is essential to clarify the interactions between dislocations and precipitates. Furthermore, in recent years, in connection with the effects exerted by these microstructures, experimental studies on size effects in alloys (a phenomenon where strength increases as material dimensions decrease) have been actively conducted.
In this presentation, we describe the modeling of dislocation-precipitate
interactions aimed at understanding precipitation hardening mechanisms,
along with its implementation into DDD. Furthermore, we extend this method
to the simulation of size effects in alloys and present the results of
our investigation into the influence of precipitates on the size effect.
・The 2nd TUS Geometry & Natural Science
Speaker: Shunsuke Kobayashi（Osaka University）
Title: A Differential-Geometric Framework for Crystal Defects
: Mechanics, Analogies, and Numerical Simulations
Date: July 11, 2026, 16:00-17:00
Place: Tokyo University of Science, Kagurazaka Campus
(242 room, 4nd floor, Building No. 2)
Abstract: Crystal defects, typified by dislocations and disclinations,
are regarded as central research subjects in materials science and solid
mechanics because they strongly influence the plastic deformation and mechanical
properties of crystals. One framework for formulating the mechanical state
of crystals containing such defects is the geometric theory of crystal
defects, which combines differential geometry with continuum mechanics.
In this framework, a crystal containing defects is described as a manifold,
and dislocations and disclinations are associated with geometric quantities
on the manifold, such as torsion and curvature, respectively. This approach
provides a unified way to naturally describe defect-specific conservation
laws and their coupling with continuum mechanics. In this talk, I will
first give an overview of how crystal defects are formulated within this
framework. I will then discuss analogies with electromagnetism that arise
from this formulation, as well as the existence of mechanically equivalent
configurations of dislocations and disclinations. Finally, I will present
results obtained through numerical implementation of the theory.
2025
・The 1st TUS Geometry & Natural Science
Speaker: Masayuki Sakurai（Tokyo University of Science）
Title: Reading Life through Shape: The Biology of Nucleic Acid Structure
Date: June 14, 2025
Place: Tokyo University of Science, Kagurazaka Campus
(222room, 2nd floor, Building No. 2)
Abstract: DNA and RNA function not merely as linear sequences, but
as structured molecules whose shapes are key to their roles. In this talk,
I explore how the structure of RNA?especially transfer RNA?enables biological
function, and how structural variation is compensated through chemical
modifications or protein support. I also highlight adenosine-to-inosine
(A-to-I) RNA editing as a process in which structural irregularities are
recognized and corrected, effectively altering RNA "meaning."
Finally, I introduce technologies for detecting and directing RNA editing,
offering a new view into how life can be understood and controlled through
molecular geometry.
・The 2nd TUS Geometry & Natural Science
Speaker: Akifumi Sako（Tokyo University of Science）
Title: Quantization (matrix regularization) of Lie-Poisson algebra and
IKKT matrix model
Date: July 19, 2025
Place: Tokyo University of Science, Kagurazaka Campus (Room 222)
Abstract: PDF
・The 3-th TUS Geometry & Natural Science
Speaker: Akinori Yamanaka（Tokyo University of Agriculture and Technology）
Title: Integration of Phase-Field Simulation of Microstructural Evolution
with In-situ Observation using Bayesian Data Assimilation
Date: July 26, 2025
Place: Tokyo University of Science, Kagurazaka Campus
(222room, 2nd floor, Building No. 2)
Abstract: The phase-field method is an effective numerical modeling and simulation approach for microstructural evolution (e.g., grain growth, grain boundary migration, and phase transformation). To improve the predictive accuracy of phase-field simulations, the parameters in the model must be accurately calibrated using experimental data. In this presentation, I will introduce an approach that integrates in-situ experimental observations with phase-field simulations through data assimilation based on Bayes’ theorem, enabling precise parameter estimation.
・The 4th TUS Geometry & Natural Science Seminar
Speaker: Masashi Mizuno（Nihon University）
Title: TBA
Date: October 4, 2025
Place: Tokyo University of Science, Kagurazaka Campus
(222room, 2nd floor, Building No. 2)
Abstract: TBA
・The 5th TUS Geometry & Natural Science（Scheduled for October）
※ This seminar is scheduled to be held on Saturday.
Organizer： Naoyuki Koike，Makiko Tanaka，Susume Hirose，Akifumu Sako,
Katsuhiko Suzuki, Tetsuro Nikuni, Makoto Tadokoro, Kazuya Otsubo,
Shinji Ogihara, Akiyuki Takahashi, Masayuki Sakurai, Hisanori Ohashi,
Kurndo Baba，Daisuke Yamakawa, Yasufumi Nitta, Natsumi Oyamaguchi,
Toru Kajigaya, Tomoki Fujii, Naoki Kimura, Koya Shimokawa,
Kazutoshi Inoue, Takamasa Tsukamoto,