April 27, 2026
The University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI)
The Kavli IPMU is proud to announce the beginning of our annual Science Cafe 2026 series "Universe", co-hosted with the Tamarokuto Science Center. This event will be in English.
Interested in testing your knowledge of the latest advances in Physics and Mathematics? We look forward to seeing you there. Pre-registration is required.
Science Cafe 2026 "Universe"
Time & Date: 1:30PM - 3:00PM, June 28 (Sun)
Venue: Tamarokuto Science Center Event Hall
How to Count to 2875 Without Starting at One: The Art of Curve Counting
Speaker: Zhao Lutian (趙 鷺天)(Kavli IPMU Project Researcher)
Difficulty level: Junior high school and above (the content is more appropriate for high school students. The event will be in English with no Japanese interpretation)
Seats: 50 (First 50 applicants only)
Admission: 400JPY to cover tea time costs (note: Visitors will also be required to pay the 520JPY entrance fee for the Tamarokuto Science Center. )
Click here to register (Tamarokuto Science Center)
Introduction:
In the third century BCE, Apollonius of Perga asked how many circles can perfectly touch three given circles. The answer—eight—is a classic puzzle of enumerative geometry: the art of counting shapes subject to strict rules.
But how do we count objects in spaces far beyond human intuition? You cannot sketch a six-dimensional space to see what is inside it. Instead of trying to draw curves, mathematicians use intersection theory. This allows us to translate visual geometry into algebraic machinery, letting us count by tracking exactly where abstract conditions collide.
A famous triumph of this method is proving that a general quintic threefold hides exactly 2875 straight lines. Hermann Schubert pioneered the tools to compute this in the 1890s, but a century later, string theory completely revolutionized the field. By studying complex spaces called Calabi-Yau manifolds, physicists handed mathematicians unexpected, highly powerful new formulas for counting curves.
In this talk, we will explore how geometry, algebra, and a surprising dialogue with physics come together to solve the ultimate puzzles of the invisible.
About the speaker
Lutian joined Kavli IPMU in 2024. His field of expertise is mathematics
