不人气的大狸子
Tanuki
The 2026 Fields Medals were awarded this week at the International Congress of Mathematicians in Philadelphia. The four recipients were Yu Deng, Hong Wang, John Pardon and Jacob Tsimerman.
Two of them, Yu Deng and Hong Wang, are Chinese mathematicians, making them the first Chinese nationals to receive the Fields Medal. Deng is currently a professor of mathematics at the University of Chicago. He entered Peking University in 2007, later transferred to MIT, and received his PhD from Princeton University in 2015.
Deng was awarded the medal for his work on partial differential equations and mathematical physics. Among other results, he and his collaborators gave a rigorous derivation of the Boltzmann equation from deterministic hard-sphere dynamics, addressing a problem connected to Hilbert’s sixth problem and the mathematical foundations of statistical physics.
But Chinese Touhou fans soon noticed something else in the official profile video produced for the award.
On the desk beside Deng’s computer, there are two fumos: Reimu and Alice.
This is not a photograph taken from a private account or an object identified through several layers of internet speculation. The figures are visible in the official Fields Medal profile video filmed in his office.
They also seem consistent with Deng’s publicly stated interests. On his personal University of Chicago webpage, he writes:
> “I like poetry, stories, fiction, puzzles, manga, Go, soccer, and anything that is beautiful and fascinating.”
A recent Chinese-language interview reported that he has been interested in anime for more than ten years. According to the interview, he began watching more anime and reading novels after moving abroad, and his interests range from romance to science fiction. When he received the email informing him that he had won the Fields Medal, he was apparently reading a romance novel. He read the message, felt relieved — and then went back to the novel.
The same profile video also appears to show a mug featuring Sayaka Saeki from Bloom Into You, so Touhou is clearly not his only interest in Japanese media.
Further evidence comes from the verified WeChat account of the Beijing International Center for Mathematical Research.
In a post featuring a mathematics problem by Yu Deng, titled “Dance of the Dolls” (人偶之舞), the problem begins with Alice possessing 101 dolls, one of which is explicitly named Shanghai. The dolls move around a circular track at different constant speeds, and the task is to prove that Alice can choose their speeds so that Shanghai repeatedly comes arbitrarily close to all the other dolls.
Below is the English translation of the question. If you are interested in mathematics, you can try it yourself:
Alice has 101 dolls. They move counterclockwise at constant speeds along a circular track of circumference 1, starting from their respective initial positions. One of the dolls, Shanghai, has a fixed speed of 1.
Prove that Alice can choose the speeds of the other 100 dolls and select a constant C such that the following statement holds:
Regardless of the initial positions of the dolls, there exist infinitely many positive integers n such that, when Shanghai returns to her starting point for the nth time, the distance between Shanghai and every other doll is at most C * n^(-0.01).
Note: Collisions between the dolls do not change their speeds or directions.
Even without that additional story, however, the figures in the official video provide fairly direct evidence that one of the most accomplished mathematicians of his generation is also a Touhou fan.
I do not think the significance of this is that Touhou somehow “produced” a Fields Medalist, or that the fandom requires famous people to validate it. It is interesting for a different reason.
Touhou has now existed for long enough that several generations of fans have grown up with it. People who encountered Touhou through the games, music, illustrations, doujin works or internet culture are now working throughout academia, engineering, art, education and many other fields. Their connection to Touhou may no longer be the most visible part of their public identity, but it has not necessarily disappeared.
In Deng’s case, Reimu and Alice simply remain beside his computer while he works on some of the most difficult problems in modern mathematics.
That feels like a small but rather beautiful milestone for the Touhou community.
And yes, the obvious joke practically writes itself:
A mathematician who studies extremely complicated dynamical systems naturally became a Touhou fan.
Two of them, Yu Deng and Hong Wang, are Chinese mathematicians, making them the first Chinese nationals to receive the Fields Medal. Deng is currently a professor of mathematics at the University of Chicago. He entered Peking University in 2007, later transferred to MIT, and received his PhD from Princeton University in 2015.
Deng was awarded the medal for his work on partial differential equations and mathematical physics. Among other results, he and his collaborators gave a rigorous derivation of the Boltzmann equation from deterministic hard-sphere dynamics, addressing a problem connected to Hilbert’s sixth problem and the mathematical foundations of statistical physics.
But Chinese Touhou fans soon noticed something else in the official profile video produced for the award.
On the desk beside Deng’s computer, there are two fumos: Reimu and Alice.
This is not a photograph taken from a private account or an object identified through several layers of internet speculation. The figures are visible in the official Fields Medal profile video filmed in his office.
They also seem consistent with Deng’s publicly stated interests. On his personal University of Chicago webpage, he writes:
> “I like poetry, stories, fiction, puzzles, manga, Go, soccer, and anything that is beautiful and fascinating.”
A recent Chinese-language interview reported that he has been interested in anime for more than ten years. According to the interview, he began watching more anime and reading novels after moving abroad, and his interests range from romance to science fiction. When he received the email informing him that he had won the Fields Medal, he was apparently reading a romance novel. He read the message, felt relieved — and then went back to the novel.
The same profile video also appears to show a mug featuring Sayaka Saeki from Bloom Into You, so Touhou is clearly not his only interest in Japanese media.
Further evidence comes from the verified WeChat account of the Beijing International Center for Mathematical Research.
In a post featuring a mathematics problem by Yu Deng, titled “Dance of the Dolls” (人偶之舞), the problem begins with Alice possessing 101 dolls, one of which is explicitly named Shanghai. The dolls move around a circular track at different constant speeds, and the task is to prove that Alice can choose their speeds so that Shanghai repeatedly comes arbitrarily close to all the other dolls.
Below is the English translation of the question. If you are interested in mathematics, you can try it yourself:
Alice has 101 dolls. They move counterclockwise at constant speeds along a circular track of circumference 1, starting from their respective initial positions. One of the dolls, Shanghai, has a fixed speed of 1.
Prove that Alice can choose the speeds of the other 100 dolls and select a constant C such that the following statement holds:
Regardless of the initial positions of the dolls, there exist infinitely many positive integers n such that, when Shanghai returns to her starting point for the nth time, the distance between Shanghai and every other doll is at most C * n^(-0.01).
Note: Collisions between the dolls do not change their speeds or directions.
Even without that additional story, however, the figures in the official video provide fairly direct evidence that one of the most accomplished mathematicians of his generation is also a Touhou fan.
I do not think the significance of this is that Touhou somehow “produced” a Fields Medalist, or that the fandom requires famous people to validate it. It is interesting for a different reason.
Touhou has now existed for long enough that several generations of fans have grown up with it. People who encountered Touhou through the games, music, illustrations, doujin works or internet culture are now working throughout academia, engineering, art, education and many other fields. Their connection to Touhou may no longer be the most visible part of their public identity, but it has not necessarily disappeared.
In Deng’s case, Reimu and Alice simply remain beside his computer while he works on some of the most difficult problems in modern mathematics.
That feels like a small but rather beautiful milestone for the Touhou community.
And yes, the obvious joke practically writes itself:
A mathematician who studies extremely complicated dynamical systems naturally became a Touhou fan.