I'm really excited about this paper :) With George Domat and Hannah Hoganson, we show that there are exactly 3 "coarse equivalence" classes of homeomorphism groups of countable, compact ordinals in the order topology, giving explicit models for each one! arxiv.org/abs/2607.01196

By the way, I’m soliciting suggestions for interesting Perron numbers (algebraic integers) of manageably small degree. This one is sometimes called Lehmer’s number (I think?) and is a very small Salem number. If you have a vaguely hipster favorite Perron number please let me know :)

Here’s an irreducible train track map whose transition matrix has characteristic polynomial x^12 - x^7 - x^6 - x^5 + 1 It represents an outer automorphism of a free group of rank 10, which is a good deal higher than the theoretical minimum of 6. Maybe we cannot go lower, which would surprise me!

Very insightful short essay by Petra Schwer ( mathstodon.xyz/@PetraSchwer ): ‘The meaning of doing mathematics’ “(Can AI solve all math? What do we actually mean by doing mathematics? How do we communicate mathematics? What is mathematics beyond problem solving?)” arxiv.org/abs/2509.15998

Ummmmm guys... I just went to canvas to do something for class and this is all I can see. IT has said nothing and my students need to use this to submit assignments and I need it to grade and also what information are we being blackmailed with and...Well, things are going great!

I’m looking a lil stupid just as often as I can stomach. Anyone else? read.alonzo.zip/flexing-my-e...

hi, yes, please tell me why am i getting facile spam emails from AI about a corner of my research?

Subgroupoids of groups are cool :) seems like a useful framing applicable to any situation where you have many (conjugacy classes of) subgroups... www.robbielyman.com/blog/subgrou...

is anybody thinking about subgroupoids of groups? super interesting framework to consider a number of common constructions in group theory…

I propose to make universal the old policy of the Blackfriars conference at the American Shakespeare Center: If you do not end your paper on time, you will be forced to exit, pursued by a bear. Literally, a bear will come take your paper from you.

So is coding dead yet, or what? My students want to know. www.robbielyman.com/blog/crying-...

I’m taking the train from Newark to DC tonight to give a talk in the Logic Seminar at the University of Maryland. I love taking the train places, it’s my favorite method of travel.

This week, I ponder the question: what is the point of the work I do? If I do say so myself, I’m unusually clear-sighted about the point of (my) work. The existential angst is obviously present but manages not to overwhelm the essay 😁 read.alonzo.zip/why-are-ther...

dang, i was participating in a rutgers mentoring program that just got canceled as part of our new president’s decision to close the office of university equity and inclusion

Come learn and socialize with us next week (1/24) at NYC's second Zig Day :) Huge thanks to @recurse.com for hosting! luma.com/1ywvn8mp?tk=...

“i want back my rocking chairs, / solipsist sunsets, / & coastal jungle sounds...” A poem by Renee Nicole Good, who was murdered by ICE earlier today. lithub.com/renee-nicole...

"I guess if this bit of the post has a point it's that trans women librarians are salt of the earth, tough as nails, some of the best people I know, and every library system should give them a raise and the best health insurance policies out there." read.alonzo.zip/go-to-the-li...

MTA Admits To Fabricating Large Parts Of Subway Map https://theonion.com/mta-admits-to-fabricating-large-parts-of-subway-map/

read.alonzo.zip/2025-in-books/ I read 11 more books in 2025 than 2024; here's hoping I keep that upward trend for next year :)

I am trying out this whole "you can just write things" thing read.alonzo.zip/surely-he-ha...

anyway, here's wonderwall.

I’m looking for 100% Filipino people who are willing to submit a cheek swab test in hopes for a genetic match to my aunt, who is battling blood cancer. The registry for stem cells doesn’t have many Filipino people in it, and joining it could help many. Please share/reach out to me! bit.ly/4aiUIKQ

Honestly, I bet some of my students must make *great* ex-boyfriends with the way I'm getting emails about failed final exams.

sufficiently advanced math indistinguishable from ghosts

Truly regrettable mistake by the maintainers of arXiv. The arXiv is an incredible piece of commons in a world of paywalls, and I want it to live up to its potential. Reinscribing 100 years of English-language hegemony in science is not the way.

Not to "it's just the wangdoodle in the category of wingnuts", but colimits are so much simpler than you might initially think! Say F : J -> Set is a functor, the Grothendieck construction gives you a category ∫ F which has an underlying graph. The colimit of F is the set of connected components.

We featured Ryan Goldstein’s Felt, Bruce Hill’s Tomo, and Frederic Kettelhoit’s Kombucha. Thank you to everyone who came to our December Localhost. We’ll see you next year! 📸 Photos by @robbielyman.com

delightedly and regretfully, i must inform you that i am back on my 1.5-categorical bullshit 😈

i fixed my glasses by unscrewing and rescrewing the tiny screw that holds in the nose grip, changing out a broken one for a non-broken one… easy task but damn if i’m not feeling like “you can call me Bob the Builder bc YES I CAN FIX IT”

I frequently get spammy solicitations to publish papers in journals of dubious quality and relevance to my work, but I noticed a *big* uptick the past couple days since posting this to the arXiv. Anyway I was just thinking how nice it would be if humans read this paper too. 🥹

i wasn’t in the marathon yesterday, but i did run 10 miles for the first time in a long time, maybe ever, so today i’m walking around like i’m playing a game of QWOP

🌱 Interested in coming to RC? Have any burning questions? Join us to learn more about what attending is like! You'll get to ask questions and hear directly from faculty and current Recursers about their experiences. We’re hosting an info session on Tues, Oct 21 at 5:15 ET. ⬇️

Fredric Jameson #remix: It's easier to imagine that #LLM #AI is consciousness than it is to admit the fact that language can be produced without it.

like, you bitches don’t even know the difference between vintage and arXiiiiiiiiiiv, like

I have finally done it

I joked “I’d pay money for a good open source operating system” and I’m not sure people got that the joke part is bc I already do 🍎

Zig NYC #7 is coming up next month! come talk to my about why the best programming language is Rust or something, and I'll argue otherwise :) lu.ma/un8ual6a?tk=...

Missed our last info session? We're hosting another on Wed 9/3 at 5 pm ET! If you're thinking of spending 6 or 12 weeks building whatever excites you most, join us! You’ll get to ask questions and hear directly from faculty and current Recursers about their experiences. RSVP: luma.com/z6ccwozs

Thinking about applying to a Recurse Center (RC) batch? If you want to spend 6 or 12 weeks building what excites you (compilers! games! languages! research! machine learning! art!) within a community of thoughtful, curious peers, come join our info session this Thursday! lu.ma/86a0fqdn

oh dang, i waited 20 minutes after the start of signups for the JLPT N3 and all the seats in NYC were gone. so I guess I'm going to Philly!

2030: a bunch of geometric group theorists open an ice cream shoppe called The Asymptotic Cone

Literally *the* dominant emotional vibe of my day job: managing the student's frustration that they aren't already fluent combined, much of the time, with them ignoring offered feedback and being disinterest in consistent practice.

“i have to use AI because i’m bad at drawingggg 😭😭😭”

i just did a workshop with kids about making comics. emphasized that ANYONE can make comics. you don't have to be a "good" artist. you find a story that matches your art style and you do it and it's awesome. and a kid who NEVER PARTICIPATES got out from under a desk and PARTICIPATED and had a blast.

It is easy to feel this way but I truly think, for trans writers at least, writing books now is urgent. Write good books about your friends, get them printed, get them widely distributed, get them in the world. There has never before been an opportunity like the one we currently possess to do this.

back in the day i lived in Somerville, MA above a flower shop which was bought by a graphic designer who used it as a studio space and a little gallery.

Just typing `eq.not nothing` in @typst.app and humming happy snatches of Vanessa Carlton's 2002 album title "Be Not Nobody" to myself