Lazy Christmas Eve, waiting for Santa with my first grader on my lap, engrossed in a Rubik’s cube.

Obligatory post

My first grader is VERY amused by the score of this game. 🙄

Pre-order Chad’s book, y’all! 👇

Hey #MathSky! Are you posting to the arXiv soon? Do the following first in Overleaf: File→Settings→Compiler Change pdfLaTeX to XeLaTeX Then put this in your preamble: \usepackage{fontspec} \usepackage[english]{babel} \babelfont{rm}{Carlito} % Calibri clone Spread the word!

I spent two years in the Trump administration. During that time, I saw how the president handled national security decisions. One of my biggest takeaways was this: He fantasized regularly about maiming & killing unarmed civilians. Actually.

Penultimate harvest of 2025. The last 12 lbs of kiwi, 24 lbs of Yuzu, and a handful of flying dragon citrus. The colors look a little off because this picture was taken 12 minutes after sunset.

Leftovers

Too funny not to share!

Hearing news that Carl Dieffenbach, the Director of the Division of AIDS at #NIH (NIAID), has been removed from his position because he was "not aligned with HHS/OMB." Russell Vought continues to remove great scientists as part of the Project 2025 mission to politicize and destroy NIH. 🧪 1/

Today’s xkcd made me cry. In a good way. xkcd.com/3172/

More fall fruit that I’m growing. Fun facts: the kiwis can’t be picked until the first freeze (last week). The Yuzu has survived single-digit (F) temperatures.

This talk was given on September 12 in the New York Combinatorics Seminar. Here's a link to the recording. youtu.be/BX6VkFHwn-g?...

Fall in my orchard. Flying dragon hardy citrus in front of Fuyu persimmon fall foliage.

I got *a lot* of positive feedback about this sign tonight from (parents of) trick-or-treaters.

You know who’s not? #GoMs #TridentsUp 🔱

Looking for suggestions! I rarely watch mainstream movies, but I enjoy international films, especially from non-Western cultures. But I don’t know how to find the best ones. Do you have any favorites? Here are some I’ve watched in the past few years.

I'm sure this will be controversial, because it's a pro-AI post on a notoriously anti-AI site (BlueSky). I'm almost 45 and have never written a UNIX shell script. So I asked ChatGPT for help, and it gave me the following in a matter of seconds. It's really good at this sort of thing. 1/2

One of the silver linings of being a lifelong fan of one of the least successful baseball teams is that I had COMPLETELY forgotten how stressful this is! 😩

GET OUT THE MUSTARD AND RYE BREAD!!! I can hear Dave Niehaus calling it. 🔱🔱🔱🥹

BIG DUMPER!!! 🔱🔱🔱🔥🔥🔥

This is just embarrassing. Has to be one of the worst strike calls of the year. #TridentsUp 🔱

Watching the game with my kids. The Mariners score, and the 9 changes to a 10. My 2-year-old son Felix looks back at me, points at the TV, and says “mo mo! mo mo!” as he puts his hands together to make the baby sign for “more”. 🥹😂🔱💙💛

Mathematical Finance event in Wellington called the New Zealand All Black-Scholes

Numerical Linear Algebra event in Florida called the Tampa Bay Rayleigh quotients

Group theory event in India called the Lucknow Supersolvable Giants

Taylor series event in Spain called Real Analytic Madrid.

Back-to-back topology events in the Twin Cities called the Minnesota Hopf Lynx and the Minnesota Wild Knots

Algebraic number theory event in Southern California called The Los Angeles Ramified Primes

Lotka-Volterra event in Tennessee called The Nashville Predator–Prey Models

Number theory event in Minneapolis called the Minnesota Twin Prime Conjecture

An Alexandrov geometry event in New York called The Brooklyn Polyhedral Nets

Geoduck

Clemson has been designated a National Monarch Butterfly City, and there is a public art installation of 20 fiberglass butterflies all around town. Look closely, one of them appears to have some hidden mathematics on its underside! #IllustratingMath #Mathober

Question for #MathSky: What is your favorite result, trick, or technique involving generating functions? Whenever I ask a question like this I always learn something new.

Here's what a Mississippi judge wrote in 1979 about school vaccine mandates. Things have changed. www.gravityisgone.com/mississippi-...

I'm 6'1" and 222 lbs. So if I gain 5 lbs before my next physical, I'll have a BMI index of 30 and will thus be eligible for a COVID vaccine. Or I could just not exercise for a few months and claim high risk due to "inactivity." Which should I shoot for? Make America Healthy Again! 🙄

Hey #MathSky, have any of you read this book? "An engrossing saga of a young mathematician caught between two countries, two cultures, two eras, and two loves. Set against the violent turmoil of the Chinese Cultural Revolution..." www.penguinrandomhouse.com/books/690668...

The pawpaws are ripe! The only temperate soursop in the world.

If you could get a crib in any five cities (five cribs) of your choice in the world, which would you choose? - NYC - Cape Town - Santa Barbara - Tokyo - Reykjavik

When you unexpectedly run into colleagues because two workshops at the same institute happen to be scheduled during the same week. @mathprofcarrie.bsky.social @icerm.bsky.social

Excited to be heading up to Rhode Island for the Illustrating Mathematics workshop at ICERM! Looking forward to seeing @mathzorro.bsky.social, @msmathcomp.bsky.social, @mathgrrl.com, @stevejtrettel.bsky.social, ‪@peterkagey.com, @henryseg.bsky.social. Did I miss anyone?

Same energy

ChatGPT 5.0 was released today. I was curious to see how it would handle a few visual algebra questions. Answer: not good. I'm safe for at least a few years! This was its attempt at constructing the subgroup lattice of D₄, with the group D₄ at the top. (It's in the middle.) It's also missing 2.

Four types of figs from my trees: Celeste, Brown Turkey, LSU Gold, and Chicago Hardy (the purple ones).

I picked nearly 11 pounds of figs from my trees this evening.

Vaccination schedules on the CDC website have already started changing under RFK Jr. So we published a guide to the evidence-based vaccine recommendations in place *before* all 17 members of the advisory panel were abruptly dismissed by the new admin. www.scientificamerican.com/article/see-... 🧪

Question for #MathSky: what are some fundamental results in ring theory that fail w/o the assumption of unity? Here are 3 examples: #1. {r₁x₁+⋯ +rₙxₙ : xᵢ∈X} = ∩ ideals that contain X Ex: X={2} in the ring R=2Z[x], b/c 2∉LHS but 2∈RHS #2. maximal ideal => prime ideal Ex: I=4Z in R=2Z 1/2

I will definitely be using this example the next time I teach abstract algebra to warn students of using AI. The claim that 2x ∈ (2,x) but 2 ∉ (2,x) and x ∉ (2,x). is gold! What are your favorite examples of things like this?