Crooked Timber — 10/24/2025
On the longer time scale that we feel in nature, the violence of colonial capitalism seems almost fleeting. ‘Mother Nature will outlast all of this’, Barkandji man Woddy Harris told me, gesturing across his hometown of Wilcannia, two hours’ drive…
Computational Complexity — 10/23/2025
This fall, for the first time at Illinois Tech, I’m teaching Introduction to Theory of Computation. While I’ve taught a variation of this course a couple dozen times, I last taught this class Spring 2016 at Georgia Tech. Intro Theory is a course…
The Aperiodical — 10/22/2025
Double Maths First Thing is beautiful, it’s simple and it’s wrong Hello! My name is Colin and I am a mathematician on a mission to share the joy and love that comes from doing maths. As the amazing Jo Sibley says, if you love someone, set them a…
Computational Complexity — 10/21/2025
Several people emailed me that September 16, 2025—written as 9-16-25 in the US—represents the integer side lengths of a right triangle.9-16-25 is the only such triple that is also a valid date. This kind of mathematical alignment only happens…
The Aperiodical — 10/20/2025
Somehow, I’ve been awarded the MEGA grant, from Matt Parker and Talking Maths in Public, for a ridiculous public maths project. I’d better get on that, then! My plan is to go to the beach and use great big cookie cutters in the shape of the spectre…
Math ∩ Programming — 10/19/2025
Polyhedral optimization is a tool used in compilers for optimizing loop nests. While the major compilers that use this implement polyhedral optimizations from scratch,1 there is a generally-applicable open source C library called the Integer Set…
Crooked Timber — 10/19/2025
Crooked Timber — 10/19/2025
Within ten minutes I regretted my decision to walk to Creedon Street in the outback town of Broken Hill. At first, I thought it was the shoes. Stupid things I’d bought on the internet, they were little more than plastic-coated cardboard soles…
Computational Complexity — 10/18/2025
In 2001 I supervised Charles Lin’s Master’s Thesis, which was on Private Information Retrieval.In 2025 I supervised Charles Lin’s Master’s Thesis, which was on Ramsey Theory.These are different people. To celebrate the second one’s thesis, I took…
Crooked Timber — 10/16/2025
One of the big puzzles in the last months, for those observing the politics in the US and elsewhere, is this: why is there apparently so little protest against the attacks on democracy and the rule of law, and why does it happen in some but not…
Computational Complexity — 10/15/2025
Each fall I try to predict the theory computer science faculty job market to come and give suggestions to those going after them. Get set for a rocky ride, with AI’s disruption of computer science, fiscal stress at universities, and new U.S….
The Aperiodical — 10/15/2025
Double Maths First Thing almost forgot to put this line in! Hello! My name is Colin and I am a mathematician on a mission to spread the joy and delight of doing mathematical things. This week I am mainly getting to grips with reluctantly becoming…
The Aperiodical — 10/14/2025
I was asked recently by a first-year maths undergrad student if I could recommend any books on problem-solving, as they were hoping to develop their problem-solving skills. Asking around some maths communication colleagues has resulted in an…
Crooked Timber — 10/9/2025
A European justice minister who does have principles! The EU “chat control” proposal I wrote about the other day has been scuppered by Germany’s justice ministry saying forcefully that it will never support this particular form of mass…
Computational Complexity — 10/8/2025
A few comments to last week’s post Computers Don’t Want suggested that human brains are just advanced computers, yet still possess agency and desires. But are we just Turing machines? I wrote about this question before but let’s revisit in the…
The Aperiodical — 10/8/2025
DMFT is grateful for the last minute. Hello! My name is Colin and I am a mathematician on a mission to spread the joy and delight of doing maths and solving problems. Today I went to a school in Poole to talk about my career in maths and computing…
Crooked Timber — 10/7/2025
I’m publishing an email I just sent to Ireland’s Minister for Justice, Jim O’Callaghan, on a truly hideous and anti-democratic European law that Ireland is strenuously supporting. It’s looking like Germany, which was strong on data protection, may…
The Aperiodical — 10/7/2025
I’m trying something a bit different. Here’s a ten-minute video about a sequence I found on the OEIS. (I’ve also put this video on YouTube, but I’m anxious about having a copy of my videos somewhere that else) The sequence is A276573, the infinite…
The n-Category Café — 10/7/2025
I’m trying to better characterize two maximal subgroups of the group of automorphisms of the exceptional Jordan algebra, whose intersection is the Standard Model gauge group.
Computational Complexity — 10/5/2025
You used AI in your work. Do you hide it or brag about it? 1) In 2002 there was a movie Simone about an actress who is really an AI. The Wikipedia entry tells the entire plot. I saved time by reading it in two minutes rather than watching it in 2…
Crooked Timber — 10/5/2025
The Aperiodical — 10/4/2025
The next issue of the Carnival of Mathematics, rounding up blog posts from the month of September 2025, is now online at IoannaGeorgiou.com. The Carnival rounds up maths blog posts from all over the internet, including some from our…
The Aperiodical — 10/3/2025
Here’s a round-up of maths news stories from this month we haven’t otherwise covered on the Aperiodical (not including, of course, the important enneahedron news Christian just posted about). MathJax, a Javascript display engine for typesetting…
The Aperiodical — 10/3/2025
A nice person called Payton Asch sent me an email with an observation about the Herschel enneahedron: It looks like the underlying polytope for the enneahedron is a triangular bipyramid (two tetrahedra stacked on top of each other) or the dual…
Crooked Timber — 10/3/2025
(I wrote this piece a week or so ago, meant to do a bit more work but haven’t got around to it. Hence slightly dated allusions) The culmination of Donald Trump’s state visit to the UK was a press conference at which both American and British…
The Aperiodical — 10/2/2025
We’ve gone crashing into October and that means it’s also #Mathober, an annual maths/art celebration taking place on the internet. If you’re into maths or art, or both, and would like to try producing something creative this month, on an informal…
Fractal Kitty — 10/1/2025
This is the post I’ll update with this year’s Mathober art. Check back and see what’s been added throughout the month. Link, Deviation, PolyhedronStrongly, Digraph Sink, Partial SumNotation (find the sigma)P5.js sketchesLink, Deviation,…
Computational Complexity — 10/1/2025
I read through the new book If Anyone Builds It, Everyone Dies by Eliezer Yudkowsky and Nate Soares. “It” refers to Artificial Super Intelligence (ASI). A very short version of the authors’ argument: You can view advanced AI as though it has its…
Crooked Timber — 10/1/2025
I have a long-standing pet peeve about the conflation of academic freedom and freedom of speech, especially in the context of (purported) campus debate. In order to illustrate why one should not conflate academic freedom and freedom of speech, I…
Computational Complexity — 9/29/2025
Martin Kruskal was born Sept 28, 1925 and passed away on Dec 26, 2006, at the age of 81 (we did two posts for his memorial, here and here). Today, Sept 28, 2025, is his 100th birthday. His son Clyde Kruskal wrote today’s blog post as a tribute to…
Fractal Kitty — 9/28/2025
Kristin Henry has been providing SciArtSeptember prompts each year. I incorporated all of the prompts into a single sketch this year. 1. Fluid 2. Coral 3. Inertia 4. Diffusion 5. Skeleton 6. Growth 7. Virus 8. Permutation 9. Element 10. Algae 11….
Abuse of Notation — 9/27/2025
“My life is like a prison” I wrote this in my personal website when I was 14. I was quite correct in pinpointing the problem, pinpointing how I, and many other people, felt, but I was off at identifying the cause — I thought, that I was kept in…
Crooked Timber — 9/26/2025
A while back I wrote a series of posts about the 1998-9 Kosovo conflict. If you’re interested, here they are: Prelude to War, The Serbian Ascendancy, Things Fall Apart, And So To War. This post continues that story up to the unsuccessful…
Fractal Kitty — 9/25/2025
Today is math storytelling day, so I thought I would make a visual coloring sheet as a prompt for others. What characters live in this world? What stories are there to tell? What number system would you have? What mathemagical spells would you…
Computational Complexity — 9/25/2025
A few weeks ago I took an Uber to a regional airport and was picked up by a Tesla. The driver used FSD, so-called Full Self-Driving, never touching the steering wheel during the entire trip. Should you tip a driver who just sits there? In the end I…
Computational Complexity — 9/25/2025
A guest post by Eric Allender prompted by an (incorrect) P ≠ NP proof recently published in Springer Nature’s Frontiers of Computer Science.For a time, I served as Editor-in-Chief of ACM Transactions on Computation Theory, and in this role I had to…
Math3ma — 9/25/2025
Over the past couple of years, I’ve been learning a little about the world of quantum machine learning (QML) and the sorts of things people are thinking about there. I recently gave an high-level talk on some of these ideas in connection to a…
Math3ma — 9/25/2025
Next up on Good Reads: The Princeton Companion to Mathematics, edited by Fields medalist Timothy Gowers. This book is an exceptional resource! With over 1,000 pages of mathematics explained by the experts for the layperson, it’s like an…
Computational Complexity — 9/23/2025
STUDENT: What did you do before the web to find papers?BILL: We went to the library and copied papers to read later.STUDENT: Did you read them later?BILL: Well, uh,hmm, …BILL to a professor in his 80’s: What did you do before copy…
Crooked Timber — 9/22/2025
I’m in the midst of doing research, teaching, and outreach activities on a set of questions around economic growth and its relationship to what we value. My research team has Tim Jackson visiting tomorrow, who will give a talk on postgrowth…
Crooked Timber — 9/21/2025
Computational Complexity — 9/17/2025
When announcing Open-AI’s latest release last month, Sam Altman said “GPT-5 is the first time that it really feels like talking to an expert in any topic, like a PhD-level expert.” Before we discuss whether GPT-5 got there, what does “PhD-Level…
The n-Category Café — 9/16/2025
The octonions have nontrivial inner automorphisms of order 3. Is this related to triality?
Crooked Timber — 9/16/2025
A trolley problem, some personal stuff, a bit of Islamic jurisprudence, and then the Honda. 1) Trolley time. Let’s start with the trolley problem. People proposing trolley problems often do them in two parts. First, there’s the anodyne one…
Fractal Kitty — 9/16/2025
Mathober is almost here! I am looking forward to seeing everyone’s creativity and take on this year’s prompts. If you’ve never participated before, now’s the perfect time to jump in!The goal of Mathober is simple: have fun, learn, grow, and play
Computational Complexity — 9/15/2025
“I’ll be on vacation so I won’t be checking email.’‘“I can’t be at the meeting since I will be out of town’‘Technology has made it so that:a) You really CAN get email when you are on vacation.b) You really CAN go to a meeting if you are out of town…
Crooked Timber — 9/15/2025
You’ve probably heard of the “Peter principle”: that employees get promoted until they reach a job they are no longer good at. And in political philosophy, there is a famous dispute between (the camps of) John Rawls and Jerry Cohen about the…
Crooked Timber — 9/14/2025
This weekend has been dedicated to the “reconstitution historique” of 1653 in Pézenas, when the États generaux of Languedoc met in what is now a small town but was then the seat of the Prince de Conti. So, a capital city back then and also a place…
The n-Category Café — 9/13/2025
Adjoint School guest post by Khyathi Komalan and Andrew Krenz
Computational Complexity — 9/11/2025
(After I wrote this post Lance tweeted a pointer to a great talk by Ronald de Wolf with more examples, and also examples of quantum proofs, see here.)I was teaching the prob method for lower bounds on Ramsey Numbers (see my slides here).As often…
Joel David Hamkins — 9/10/2025
Recently I had the pleasure to give a talk at the Conference on the occasion of Jörg Brendle’s 60th birthday at Kobe University in Japan, and I was invited to make remarks at the conference banquet given in his honor. … Continue reading →
Computational Complexity — 9/8/2025
When I first became a professor I had it all planned out, I would do research, teach and supervise students, get tenure and do more research, teach more courses, and supervise more students for the rest of my life. But once I got tenure, instead of…
Computational Complexity — 9/2/2025
Coding Style Is ImportantDoes coding style matter? We teach students how to write code and about algorithms. But, do we discuss coding style? Some people may say that style is just personal preference. But, there is undoubtedly good style and bad…
The n-Category Café — 8/30/2025
All equivalences are generated by just the strict, literally surjective ones.
Computational Complexity — 8/27/2025
This will be one of a series of posts that I’ve always wanted to write but I needed to wait until I was no longer an academic administrator.Logic is critical to proving theorems but it’s the wrong way to argue for resources.When I was such an…
Fractal Kitty — 8/26/2025
IntroductionIn this inquiry, triangles are dissected into smaller triangles with vertices labeled as either light (L), medium (M), or dark (D). Any triangles that are LMD triangles are shaded with color. Triangle playLet’s start with a triangle…
Computational Complexity — 8/24/2025
(This post was inspired by George Foreman, who passed away March 21, 2025, at the age of 76.)About 10 years ago I asked my classWhat is the best invention or tech advance of the last 50 years?Here are the answers I got NOT ranked.1) The internet….
Joel David Hamkins — 8/20/2025
This will be a talk for the Conference on the occasion of Jörg Brendle’s 60th birthday at Kobe University in Kobe, Japan, 2-5 September 2025. Many years ago, I was a JSPS Fellow at Kobe University, at the same time … Continue reading →
Computational Complexity — 8/20/2025
I’ve heard this story from a few places. A father watches Back to the Future II with his kid. The 1989 movie view of 2015 looks entirely different when in fact not much has changed except for the fashion and the lack of mobile phones. This is…
Joel David Hamkins — 8/18/2025
This will be a talk I shall give for the History and Philosophy of Science (HPS) Colloquium at the University of Notre Dame, 17 October 2025, 12:30-1:30 pm, 201 O’Shaughnessy Hall. Did Turing ever halt? Abstract. Alan Turing’s 1936 paper … Continue…
Computational Complexity — 8/18/2025
Tom Lehrer passed away on July 26, 2025, at the age of 97. I wrote a blog-obit here. One of my readers read the post and went down a rabbit hole (or did he?), which lead to a blog post about rabbit holes here. A few more notes about Tom L.1) When…
The n-Category Café — 8/15/2025
This week, 50 category theorists and software engineers working on “safeguarded AI” are meeting in Bristol.
Computational Complexity — 8/13/2025
Last month the New York Times highlighted some AI generated short movies, including Total Pixel Space, by Jacob Adler that gets philosophical about information, à la infinite monkeys. It imagines the finite number of images and video that contain…
Computational Complexity — 8/10/2025
NICK: I read and enjoyed your blog post on Tom L (see here). I then spent 40 minutes down a rabbithole listening to his music on YouTube.BILL: You call that a rabbit hole?! A while back I spent 3 hours reading questions and answers on quora…
Computational Complexity — 8/7/2025
AI and VacationI’m back from my German vacation. This was my first AI vacation, by which I mean how I used AI to navigate a foreign country. Taking a picture of a hand-written menu board, not just to translate the dishes, but to get a description…
The n-Category Café — 8/5/2025
Comparing two mathematical notions of diversity.
The n-Category Café — 8/2/2025
I hear that Jack Morava died on August 1, 2025.
Computational Complexity — 7/29/2025
Tom Lehrer passed away on Saturday July 26 at the age of 97. (For other obits see this collection of ten obits here.)He worked in both of my fields of interest: Parody Songs and Mathematics. 1) He got a BA in Mathematics from Harvard, magna cum…
Computational Complexity — 7/28/2025
In a prior post I asked what criteria I used to place Prez and VP nominees since 1976 into two groups. In the book Abundance I read that since 1984 all of the Democratic nominees for Prez and VP except Tim Walz had gone to law school. I decided to…
The n-Category Café — 7/28/2025
Can the Duflo isomorphism explain the extra 1/2 in the Hamiltonian for the quantum harmonic oscillator?
The n-Category Café — 7/25/2025
Kevin Coulembier has come out with a paper claiming to prove some conjectures on 2-rigs that Todd Trimble, Joe Moeller and I made.
Math ∩ Programming — 7/25/2025
On Monday, July 14th 2025, I hosted a mini-workshop on homomorphic encryption at Google’s Portland, Oregon office. Though Portland is a small city, it’s becoming a hub for homomorphic encryption. Intel and Google both have a presence here, as well…
The n-Category Café — 7/25/2025
Announcing the Clowder Project: a wiki and reference work for category theory built using the same general infrastructure and tag system of the Stacks Project.
The n-Category Café — 7/25/2025
Did you know that Lawvere did classified work on arms control in the 1960s, back when he was writing his thesis?
The n-Category Café — 7/24/2025
First lecture in a 4.5-hour minicourse on combinatorics with species.
The n-Category Café — 7/24/2025
Second lecture in a 4.5-hour minicourse on combinatorics with species.
The n-Category Café — 7/24/2025
First lecture in a 4.5-hour minicourse on combinatorics with species.
The n-Category Café — 7/24/2025
How do you count rooted planar n-ary trees with a given number of leaves? Use Lagrange inversion!
Math ∩ Programming — 7/18/2025
I work on homomorphic encryption (HE or FHE for “fully” homomorphic encryption) and I have written a lot about it on this blog (see the relevant tag). This article is a collection of short answers to questions I see on various threads and news…
Joel David Hamkins — 7/16/2025
This will be a talk for the Fudan Logic Seminar at Fudan University, to be followed immediately by two talks for the Fudan Logic student seminar, forming a mini-conference for the logic group on 23 July 2025. Abstract. I shall … Continue reading →
Joel David Hamkins — 7/14/2025
This will be a talk for the Seminar on Frontier Issues in Logic and Philosophy The First Forum on Logic and Philosophy 逻辑与哲学前沿问题研究”学术研讨会暨第一届逻辑与哲学论坛 Changchun, China, 18-20 July 2025 Pointwise definable end-extensions of models of arithmetic and set…
Fractal Kitty — 7/11/2025
Haiku + Codewith a second take dance with the first – tethered massorbiting encores .iframe-container { position: relative; width: 100%; height: 0; padding-bottom: 100%; /* 1:1 aspect ratio - square */ overflow: hidden; …
Joel David Hamkins — 7/9/2025
This will be a lecture series on the Philosophy of Mathematics at Fudan University in Shanghai, China, 30 June – 25 July 2025, as a part of the International Summer School program at Fudan University. Lectures given by Ruizhi Yang … Continue…
Joel David Hamkins — 7/9/2025
This will be a talk for the International Conference on the Philosophy of Mathematics, held at Lanzhou University, China, 25-27 July 2025. How the continuum hypothesis might have been a fundamental axiom Abstract. I shall describe a…
Fractal Kitty — 7/3/2025
IntroductionExplore the reflection and rotation of polygons to discover the patterns that emerge. Polygon PlayLet’s start with a triangle ABC. We can rotate clockwise so that each vertex moves clockwise by one step: We can also reflect (or flip)…
Joel David Hamkins — 6/23/2025
This will be a talk for the Conference on Infinity, a collaborative meeting of logicians and specialists in Chinese philosophy here at Peking University, 24 June 2025, in the philosophy department. Abstract. I shall lay out a spectrum of…
DEONTOLOGISTICS — 6/22/2025
Here’s a recent thread on philosophy of AI from Twitter/X, in which I address rather popular arguments made by Emily Bender and others to the effect that LLM outputs are strictly speaking meaningless. I think these argument are flawed, as I explain…
Joel David Hamkins — 6/11/2025
This will be a lecture series at Peking University in Beijing in June 2025. Announcement at Peking University Course abstract. This will be a series of advanced lectures on set theory, treating diverse topics and particularly those illustrating how…
Fractal Kitty — 6/3/2025
IntroductionIn this activity, we’ll explore patterns by finding the remainders when Fibonacci numbers are divided by other numbers.ModuloSometimes, the most interesting part of dividing numbers is what’s left over—the remainder. This is where…
Abuse of Notation — 5/27/2025
title: A monad layout: microblog category: microblog tags: programming haskell — A monad is when you know how to convert $M (M a)$ to $M a$, but not $M a$ to $a$.
Abuse of Notation — 5/27/2025
The level of progress in programming language design: Shortly after the first ever programming language was created, it’s author said that the language’s whole paradigm is flawed and we should do functional programming instead*. That was 46 years…
Abuse of Notation — 5/27/2025
I want to forget Gaza. I want to forget the pain. I want to forget all dumb jokes, old song lyrics. I want to forget that most things ever happened, as remembering makes everything tedious. Forces you to become a bureaucrat of your memories, to…
Abuse of Notation — 5/27/2025
Every time you eat mushrooms, I have to try them too. Cause, if the mushrooms turn out to be poisonous and you die of slow and painful dead, I will die as well. I once dreamed that I was dying, You were beside me, I turned to you and said, “I don’t…
Abuse of Notation — 5/27/2025
The road I walk is new. It’s made not of stone, but dirt. There are no road signs yet. And no bridges to cover the rivers. The road I walk is new, so people think that it is hard. “How do swim?” “Don’t you get dirty?” “How do you cope with all that…
Abuse of Notation — 5/27/2025
Out for a walk I let go and let the city dissolve me.
Good Fibrations — 5/23/2025
I’ve felt for a long time that automorphisms of curves should control or at least exert serious force on the slopes on their Jacobians. Symmetry forces height, as I’ve written about previously in Models of Formal Groups Laws of Every Height, and…
Fractal Kitty — 5/20/2025
This is the first of a series of guided inquiries in math. If a document is preferred over a blog post, the pdf file is below:Inquiries-Week 1_ Circle ShadingInquiries-Week 1_ Circle Shading.pdf615…
Math ∩ Programming — 5/13/2025
I was inspired to browse some of Edsger Dijkstra’s essays today, and came across his speech, “Under the spell of Leibniz’s Dream”. It’s the sort of personal history I love to read, which gives one person’s sense of the world over a period of…
Joel David Hamkins — 5/12/2025
This will be an online talk for the Leeds Set Theory Seminar, 21 May 2025 1pm BST. Contact the organizers (Hope Duncan) for Teams access. Abstract: One can find in the philosophical research literature surrounding Skolem’s paradox a certain claim,…
Math ∩ Programming — 5/12/2025
Editor’s note: This essay was originally published on Medium on 2016-03-05. I have made minor edits in this republishing and added a few small retrospective notes. 2010–2011 (Year 0) I had just switched my major at Cal Poly State University from…