
Assistant Prof. @ChicagoBooth | OM & Applied AI | Most Cited Paper: Neural Collapse in AI Training | BSE @Princeton, PhD @Cornell, MS/PostDoc @Stanford
Chicago, IL
Joined November 2011
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XY Han retweeted
Here's a secret I've kept for 22 years: When I was in college, whenever I was assigned a difficult math problem that I couldn't solve, I Googled it to look for the answer--and when I found one, I had no qualms about copying it down in my homework. It didn't feel like cheating, because that's never been the part of math that appealed to me.
When I found a solution online, I loved reading through it. Seeing the clever ideas that take down a hard problem was almost like watching a slow-mo video of Usaine Bolt running: I enjoyed the aesthetic beauty of seeing something that I could never achieve myself but which I could still appreciate. And I loved zooming in on all the details, delighting in the spectacular power on display. It never felt like cheating because my goal in math was to learn math, and reading solutions I found online helped me learn math, whereas staring at a blank page did not, and trying problems and getting them wrong was often even worse. I was not a good problem solver, so a large number of problems went nowhere for me.
On the other hand, I've always been drawn to communication. So when I found a solution online, I tried to translate it into my own words, my own understanding. Was this to avoid getting caught? Perhaps. But it was more than that--I genuinely enjoyed, and learned from, the process of digesting math that was above my level and trying to put my own spin on it.
I've been thinking back on this college experience because of what AI is doing to math today. So many people I see online are fretting that AI is solving hard problems, leaving it unclear what humans should do. And saying that AI is undercutting learning because to learn math one must wrestle with problems. Perhaps I'm an outlier here, but I just don't see it that way.
I think that by being a poor problem solver my whole life, and by being more interested in story-telling and exposition, I have unwittingly been preparing myself for the AI math singularity for many years!
Regarding teaching: I really don't think we need to solve problems to learn math--because that's never how it worked for me anyway. I think we can still teach all the beautiful concepts and theories and tell all the stories than animate math, and even show people how to do calculations and how to solve problems, but then just as I used Google 20 years ago, I think we can let our students use AI however they wish but we should have students verbally explain ideas, concepts, calculations to us--or do so in writing but without access to devices. Let students use AI the way I used Google: to show them mathematics that they can then digest and internalize.
Regarding research: Nearly every paper I've published in my career has been coauthored, and in all these collaborations I was largely the one who focused on asking questions, finding examples to illustrate our ideas, and extracting a story from our results to develop into the introduction. My collaborators all helped me with these things too, but they also were way better at calculations and solving problems, so I let them take the lead on those fronts. I wouldn't have gotten anywhere in math were it not for these powerhouse collaborators. What I'm thinking now is that I can increasingly use AI for those functions, while the parts that were my focus are more solidly on the human side of things, for now at least (you can't train for them with reinforcement learning the way you can the problem solving and proving parts of math).
So, maybe it's just luck, but I feel like AI is doing the parts of math that I never liked and was never good at, and letting me soar higher into the parts I love despite my limited abilities. I suspect there are plenty more people like me. We needn't be quiet--I'm not ashamed to confess my weakness and disinterest in problem solving. Perhaps by me confessing it, it will be easier for you to do so as well.
Regarding the overall feeling of unease and disorientation many mathematicians have been expressing lately, here's my view (apologies in advance for a stretched metaphor). I feel like we have a map of the night sky with hundreds, perhaps thousands, of dark patches, and a telescope was just invented that we can point at these and illuminate many (but not all!) of them. Lots of people worry what will be left for astronomers to do as we've spent thousands of years mapping the cosmos. But many of the images from this telescope are difficult to interpret, so that's one thing for us to work on. And those dark spots that remain dark despite pointing the telescope at them--they take on an increased import and awe, for we must now wonder at why some remain dark while others do not. And with this more complete map of the cosmos we can work toward grander challenges such as uncovering the laws of physics holding this night sky together, contemplating the origins and future of the universe, looking for the larger patterns that we never previously had enough data for. In other words, what's left for us is all the things that I find truly exciting, much more so than the tedious work of filling in missing patches of our map.
Above all, there is the incredible, beautiful, challenging, and deeply personal/human act of finding stories in all this space exploration and all this new data. What a wonderful time to be a mathematician!
XY Han retweeted
I struggle to understand what drives people with little or no research background to churn out AI-generated slop in highly specialised fields like algebraic geometry or string theory. I suspect they think passing off AI-generated research as their own will make them look brilliant. In reality, they're just burdening the peer-review system and achieving the opposite.
Sure, who wouldn't want to make groundbreaking contributions across multiple fields and be recognised as a genius? But they're missing the most rewarding part of research: tackling difficult problems and learning along the way. I see little value in claiming intellectual achievements without doing the intellectual work.
XY Han retweeted
Gdmi whenever I want to try a Gemini model it’s not publicly available. Don’t bother announcing your scores if we can’t use it.
XY Han retweeted
Generating proofs you neither understand nor bother to verify is not impressive at all. At that point, you should let serious people take over.
XY Han retweeted
I was brought to tears on Sunday when the last milestone cleared. My father, a mathematician who passed in Jan, introduced me to the giants of group theory as a kid. The Classification of Finite Simple Groups (CFSG) defined my 80s college years. I can't believe I somehow got to be part of this human achievement. CFSG formalized in Lean. @leanprover
first, these results are mind blowing
second, can we appreciate how oai basically reinvented the academic peer review process from first principles?
XY Han retweeted
Many of you don't understand how serious this is, so let me break it down.
In computer science there is a famous kind of puzzle called 3-SAT. You are given a long list of yes-or-no switches and a set of rules about how they must be arranged, and you have to find a combination that satisfies every rule. The obvious way to solve it is to try every combination, but each new switch doubles the number of possibilities, so a puzzle with a few hundred switches would take longer than the age of the universe to brute force.
For decades, the smartest people in the field found clever tricks that made this a little faster, but every trick still hit the same wall: the time required kept exploding as the puzzle grew.
About 25 years ago, two computer scientists, Russell Impagliazzo and Ramamohan Paturi, working with Francis Zane, turned that wall into a formal idea.
They proposed the Exponential Time Hypothesis, which says this explosion is not a failure of human cleverness but a law of nature. No algorithm, however brilliant, will ever solve 3-SAT without the time blowing up exponentially. Nobody could prove it, but almost everyone believed it, and it became one of the foundations of modern computer science.
Researchers used it as a measuring stick. If you could show that solving some other problem quickly would also crack 3-SAT quickly, you had shown that problem was hopelessly hard too. Hundreds of papers, across scheduling, graphs, logic and much more, rest on this one assumption.
Now an internal AI model at OpenAI claims to have broken it. It says it found an algorithm that solves these puzzles meaningfully faster than the hypothesis allows, and it has checked the proof in a computer verification system called Lean.
And here is the remarkable part: the very people who proposed the hypothesis, Impagliazzo and Paturi, along with MIT's Ryan Williams, are now leading the public review of whether a machine has disproved their own idea.
So what happens next? If the disproof holds, a large part of theoretical computer science has to be revisited.
Every result that said "this problem cannot be solved faster, assuming ETH" loses its foundation, and researchers will have to work out which of those walls were real and which were simply where we stopped looking. It does not mean everything becomes easy. The new algorithm is still slow in absolute terms and this is not the famous P versus NP problem being solved.
But it means our map of what is possible was wrong in a place we were very confident about, and it was an AI that redrew it. If the disproof fails, the hypothesis survives and the field breathes out, but we will still have watched an AI produce serious, checkable work on one of the deepest questions in the discipline, closely enough that the founders of the idea had to take it seriously. Either way, something has shifted.
XY Han retweeted
After ETH falling, I woulnd't be surprised by an n^logn algorithm for 3SAT. Heck maybe even P=NP but in some absurd way that changes nothing in practice. Not dishing LLMs, they’re extraordinary! Just mad at myself for letting worst case complexity deter me from trying stuff.
XY Han retweeted
I made this prediction 3 years ago, in July 2023. Few attending my talk believed me back then.
In retrospect, replace was not quite the right word. AI won’t replace any fields. Instead, it will fundamentally reshape, and is already reshaping, fields by rewarding deep connections to real-world challenges and other disciplines.
We are announcing three new discoveries in mathematics, computer science, and physics about harmonic analysis, complexity theory, and quantum field theory.
openai.com/index/building-sc…
XY Han retweeted
I didn’t realize until today that Anthropic CEO Dario Amodei started college at Caltech and would have been one of my students if he hadn’t skipped Physics 1 (since I was head TA at the time). Given that he did skip it, it’s virtually certain that I graded his placement exam.























