Jordan Ellenberg
@jsellenberg.bsky.social
📤 3180
📥 156
📝 425
Mathematician, writer, Orioles fan, Wisconsinite, cargo shorts dad
quomodocumque.wordpress.com/2026/04/08/m...
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Minor Epiphany Concerning the World Columbian Exposition of 1894 and John Hughes
It was felt that the 1894 exposition in Chicago needed a big iron monument to rival the Eiffel Tower, and a man named George Washington Gale Ferris had the decisive insight that what the occasion d…
https://quomodocumque.wordpress.com/2026/04/08/minor-epiphany-concerning-the-world-columbian-exposition-of-1894-and-john-hughes/
18 days ago
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quomodocumque.wordpress.com/2026/04/07/b...
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Brewers 8, Red Sox 6
I was in Boston for Pesach and stuck around an extra day because some more Wisconsinites, the mighty Milwaukee Brewers, were also coming into town to play the Boston nine. CJ and I took in the game…
https://quomodocumque.wordpress.com/2026/04/07/brewers-8-red-sox-6/
19 days ago
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quomodocumque.wordpress.com/2026/04/06/a...
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Armiversary
Twenty years ago this week (I thought it was twenty years ago today, but I just went back and checked and it was April 3, 2006) I fell down a flight of stairs at MSRI and broke the absolute fuck ou…
https://quomodocumque.wordpress.com/2026/04/06/armiversary/
19 days ago
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quomodocumque.wordpress.com/2026/04/05/t...
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The College Boy and His Problems
“The High School Boy and His Problems” (pdf at link) is a 1921 book by Thomas Arkle Clark, Dean of Men at the University of Illinois. I think “The High School Boy and His Problems…
https://quomodocumque.wordpress.com/2026/04/05/the-college-boy-and-his-problems/
20 days ago
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quomodocumque.wordpress.com/2026/03/10/i...
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In which my daughter invents science
While we ate our pizza I was talking with AB about differential equations, which they’re about to start doing in calculus. We talked about y’=y. “This is why populations grow expo…
https://quomodocumque.wordpress.com/2026/03/10/in-which-my-daughter-invents-science/
about 2 months ago
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quomodocumque.wordpress.com/2026/03/09/t...
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The Irrational Decision
Ben Recht’s book The Irrational Decision: How We Gave Computers the Power to Choose for Us comes out tomorrow! I was privileged to get my copy early. And if you want an opinionated, informed,…
https://quomodocumque.wordpress.com/2026/03/09/the-irrational-decision/
about 2 months ago
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quomodocumque.wordpress.com/2026/02/27/n...
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Networking and granfallooning
It has come to my attention that students at prestigious universities are referring to the practice of cold-emailing alums of their school and asking for Zoom calls to discuss possible summer inter…
https://quomodocumque.wordpress.com/2026/02/27/networking-and-granfallooning/
about 2 months ago
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quomodocumque.wordpress.com/2026/02/25/m...
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In which I rescue Harvard’s grading system
The Harvard faculty is proposing to hard-cap A’s at 20% per course, leading to an undergraduate crashout the good old Yard has not seen the likes of since,the dining hall discontinued the Chi…
https://quomodocumque.wordpress.com/2026/02/25/my-plan-to-fix-harvards-grading-system/
about 2 months ago
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quomodocumque.wordpress.com/2026/02/18/w...
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Waiting for Godot (Gen-X rewrite)
Here’s a good use case for LLMs — they are quite good at recovering the text from files you saved on a Macintosh word processor in the early 90s and have been transporting from computer…
https://quomodocumque.wordpress.com/2026/02/18/waiting-for-godot-gen-x-rewrite/
2 months ago
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quomodocumque.wordpress.com/2026/02/06/n...
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Now pitching, Cadeler Wellvich
Barring any last-minute moves, and despite being linked to just about every big-name pitcher on the free-agent market, the Orioles will go into 2026 as they left 2025, without a clear #1 starter. D…
https://quomodocumque.wordpress.com/2026/02/06/now-pitching-cadeler-wellvich/
3 months ago
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quomodocumque.wordpress.com/2026/02/03/w...
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What’s the entropy of a random integer?
Surely people have thought about this but I couldn’t find anything on a short search. The question: let n be a random integer, say in [N,2N]. It factors as the product of p_i^a_i. So you can …
https://quomodocumque.wordpress.com/2026/02/03/whats-the-entropy-of-a-random-integer/
3 months ago
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quomodocumque.wordpress.com/2026/01/18/d...
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Dick Gross
Dick Gross died last month. Much has already been written, and during his lifetime too, about his immense contributions to modern number theory. So I won’t try to cover that here — don&…
https://quomodocumque.wordpress.com/2026/01/18/dick-gross/
3 months ago
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quomodocumque.wordpress.com/2026/01/19/i...
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It’s a good old-fashioned Wisconsin booger-freezer out there!
One of my favorite weather sayings. And I ran into a neighbor on my way home from the errand I was running so I got to say it in person, always a treat. 3 degrees Fahrenheit, sunny and windy in Mad…
https://quomodocumque.wordpress.com/2026/01/19/its-a-good-old-fashioned-wisconsin-booger-freezer-out-there/
3 months ago
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quomodocumque.wordpress.com/2026/01/17/i...
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If one is not to make a mess of life
“One must be fond of people and trust them if one is not to make a mess of life, and it is therefore essential that they should not let one down.” From E.M. Forster, “What I Belie…
https://quomodocumque.wordpress.com/2026/01/17/if-one-is-not-to-make-a-mess-of-life/
3 months ago
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quomodocumque.wordpress.com/2026/01/12/b...
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Bruhat intervals that are large hypercubes
New paper up on the arXiv! With Nicolas Libedinsky, David Plaza, José Simental, Geordie Williamson, and (unofficially) Adam Zsolt Wagner. A bunch of algebraic combinatorists! And this is a combinat…
https://quomodocumque.wordpress.com/2026/01/12/bruhat-intervals-that-are-large-hypercubes/
3 months ago
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quomodocumque.wordpress.com/2026/01/05/d...
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Dyadiku
I made a game. It’s like Sudoku but dyadic. It’s called Dyadiku. Try it! I’m very interested to see whether people find it playable and fun — in particular, does it admit a …
https://quomodocumque.wordpress.com/2026/01/05/dyadiku/
4 months ago
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quomodocumque.wordpress.com/2026/01/05/r...
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Reaching the masses (not a Marxist post)
Six popular math authors, including me, did a round-table interview for the Notices of the American Mathematical Society about talking about math to the non-academic public, or, as the Notices call…
https://quomodocumque.wordpress.com/2026/01/05/reaching-the-masses-not-a-marxist-post/
4 months ago
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quomodocumque.wordpress.com/2025/12/23/s...
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Self-portrait with about one quarter of Richard Serra’s sculpture Equal
Visit the post for more.
https://quomodocumque.wordpress.com/2025/12/23/self-portrait-with-about-one-quarter-of-richard-serras-sculpture-equal/
4 months ago
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quomodocumque.wordpress.com/2025/12/19/t...
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The American people have just one fixed idea
“The American people have just one fixed idea and, since that dominant thought is money, it follows that their spirit has a certain uniform and unpleasant dryness… prodigality is an unf…
https://quomodocumque.wordpress.com/2025/12/19/the-american-people-have-just-one-fixed-idea/
4 months ago
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quomodocumque.wordpress.com/2025/12/12/h...
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How I know zombies aren’t real
This piece of marketing doggerel from McDonald’s, concerning their Xmas-special Grinch meal, is the most foully defiling attempt to imitate Dr. Seuss’s verse I’ve ever encountered…
https://quomodocumque.wordpress.com/2025/12/12/how-i-know-zombies-arent-real/
4 months ago
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quomodocumque.wordpress.com/2025/12/03/a...
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Another example: sets of arcs and loops with bounded intersection
Yet another example of the kind of problem that falls under the sphere packing / cap set / Turan umbrella I blogged about last week. Let G be SL_2(Z) and H be upper triangular matrices. Then G/H is…
https://quomodocumque.wordpress.com/2025/12/03/another-example-sets-of-arcs-and-loops-with-bounded-intersection/
5 months ago
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quomodocumque.wordpress.com/2025/11/30/r...
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Random Americans, ethnic stereotypes, and large language models
I have been reading about the tendency of poll respondents to overestimate the size of small population subgroups (e.g. if you ask Americans what proportion of Americans are Jews, they’ll say…
https://quomodocumque.wordpress.com/2025/11/30/random-americans-ethnic-stereotypes-and-large-language-models/
5 months ago
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quomodocumque.wordpress.com/2025/11/27/n...
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“Not Vegan”
I saw a guy today wearing a hoodie that said “Not Vegan.” I’m not vegan either, not even close, but come on. This is like wearing a “Yankees Suck” shirt. I hate the Ya…
https://quomodocumque.wordpress.com/2025/11/27/not-vegan/
5 months ago
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quomodocumque.wordpress.com/2025/11/27/m...
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Mathgiving
Happy Thanksgiving to all my American readers, and hey, everyone else too — gratitude is global. In the US, this is the start of the season where people customarily think about their charitab…
https://quomodocumque.wordpress.com/2025/11/27/mathgiving/
5 months ago
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quomodocumque.wordpress.com/2025/11/24/s...
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Sphere packing, cap set, and the Turán problem are all the same thing
OK, they are not really the same thing. But I got you reading, right? Here’s the sense in which they’re all the same thing. Let G be a group and H < G a subgroup. Let m > 1 be an …
https://quomodocumque.wordpress.com/2025/11/24/sphere-packing-cap-set-and-the-turan-problem-are-all-the-same-thing/
5 months ago
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quomodocumque.wordpress.com/2025/11/08/l...
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Let us now praise United Airlines
I did manage to get home last night from Providence, despite widespread cancellations and delays caused by the government shutdown de-staffing air traffic control. United was speedy, flexible, and …
https://quomodocumque.wordpress.com/2025/11/08/let-us-now-praise-united-airlines/
6 months ago
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quomodocumque.wordpress.com/2025/11/07/i...
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I reviewed a book about the math foundations crisis for the New York Times
I thought the book had some interesting virtues but was also quite badly overwritten, and very confusing in its treatment of the mathematics. Here’s my review. For length reasons I wasn’…
https://quomodocumque.wordpress.com/2025/11/07/i-reviewed-a-book-about-the-math-foundations-crisis-for-the-new-york-times/
6 months ago
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I'm moderating an online discussion for the National Academies today, 3pm eastern, on math, risk management, and natural disasters!
www.nationalacademies.org/event/45862_...
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Risk Modeling and Management for Natural Disasters Innovation by the Numbers | National Academies
Learn more from the National Academies of Sciences, Engineering, and Medicine
https://www.nationalacademies.org/event/45862_10-2025_risk-modeling-and-management-for-natural-disasters-innovation-by-the-numbers
6 months ago
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quomodocumque.wordpress.com/2025/10/08/m...
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MacArthur Fellows: Wisconsin and Williams
The 2025 MacArthur Fellows have been announced, and I’m very pleased that two of the 22 awardees are my UW-Madision colleagues: congratulations to Ángel F. Adames Corraliza from atmospheric a…
https://quomodocumque.wordpress.com/2025/10/08/macarthur-fellows-wisconsin-and-williams/
7 months ago
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quomodocumque.wordpress.com/2025/09/30/c...
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Claudia Prieto, “Tus Ojos”
Claudia Prieto is a Venezuelan singer-songwriter about whom I know next to nothing except that she recorded this gorgeous song, “Tus Ojos,” in 2018. By the way, I found out about this s…
https://quomodocumque.wordpress.com/2025/09/30/claudia-prieto-tus-ojos/
7 months ago
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quomodocumque.wordpress.com/2025/10/03/t...
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Taylor Swift and Stephanie Burt, or: Life of a Harvard English Professor
It’s Taylor Swift album day! We listened to it last night at 11pm central when it went live. Snap reaction from AB, for whom 1989 is apex Swift and the last two albums have been too moody and…
https://quomodocumque.wordpress.com/2025/10/03/taylor-swift-and-stephanie-burt-or-life-of-a-harvard-english-professor/
7 months ago
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I gave a talk about machine learning and math
I, too, spoke at the CMSA Big Data conference where this cool math bio talk took place. If you’ve seen me give a talk about math and machine learning lately, you’ve seen some of the sli…
https://quomodocumque.wordpress.com/2025/09/26/i-gave-a-talk-about-machine-learning-and-math/
7 months ago
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Global epistasis emerges from a generic model of a complex trait (or: random walks on a hypercube with reweighting)
I still don’t really know what global epistasis is, but I really enjoyed Gautam Reddy’s talk about this paper at the CMSA Big Data conference two weeks ago. I’ll describe it, in c…
https://quomodocumque.wordpress.com/2025/09/21/global-epistasis-emerges-from-a-generic-model-of-a-complex-trait-or-random-walks-on-a-hypercube-with-reweighting/
7 months ago
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Mura Yakerson interviewed me
And we talked about math, writing, standup comedy, the art of interviewing (meta!) Mura’s whole channel is great. Bisi Agboola! Helene Esnault! Steve Strogatz! Mura’s mom! Check it out.
https://quomodocumque.wordpress.com/2025/09/19/mura-yakerson-interviewed-me/
7 months ago
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Klartag improves the sphere-packing constant
Hey! It escaped my notice until this week that Boaz Klartag has recently shown the existence of lattice sphere packings in dimension d of density at least c d^2 2^-d. This lower bound was stuck at …
https://quomodocumque.wordpress.com/2025/09/14/klartag-improves-the-sphere-packing-constant/
7 months ago
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To The Best of our Knowledge is finished
The longtime Wisconsin Public Radio show To The Best of Our Knowledge airs its last episode this weekend. You can listen to the stream at that link or you can listen to it over the airwaves tomorro…
https://quomodocumque.wordpress.com/2025/09/27/to-the-best-of-our-knowledge-is-finished/
7 months ago
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Predicament
I just learned that the origin of this word is “that which is predicated,” which is to say, more or less, any condition that can be described or specified, whether good, bad, or neutral…
https://quomodocumque.wordpress.com/2025/08/05/predicament/
7 months ago
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Still relevant: my interview in the Atlantic from Election Eve 2020, about epistemic humility, what probabilities really mean, and how not to freak out.
www.theatlantic.com/ideas/archiv...
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A Math Whiz on How to Stop Stressing About Election Forecasts
An interview with the mathematician Jordan Ellenberg about politics, election forecasting, and how to think about the future like a pro
https://www.theatlantic.com/ideas/archive/2020/11/election-probabilities-are-emotional-nonsense/616916/
over 1 year ago
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Philosophers of probability, your moment has arrived
over 1 year ago
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Somebody took the Harris for President sign off our lawn last night, but the joke is on them, the sign voted early
over 1 year ago
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It's corny I know but I do enjoy Maya Rudolph as Simulacramala.
over 1 year ago
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I actually picked up my landline and answered a poll the other day, so when you read that Harris is winning a stunning 100% of white men age 45-55 in Wisconsin, that's me
over 1 year ago
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Just thinking about actors whose names are close to old-timey adverbs. Charlize Thereon. Reese Whitherspoon. Chris Henceforth.
over 1 year ago
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Students in the UW system make up almost 3% of Wisconsin's population.
www.wmtv15news.com/2024/10/29/e...
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Enrollment inches upward in Universities of Wisconsin system
Overall enrollment in the Universities of Wisconsin system’s four-year schools ticked upward this fall compared with last year, data released Tuesday shows.
https://www.wmtv15news.com/2024/10/29/enrollment-inches-upward-universities-wisconsin-system/
over 1 year ago
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Really nice new paper by Canning, Larsen, Payne, and Willwacher which shows how far we've come in understanding unstable cohomology of M_g
arxiv.org/abs/2410.19913
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Moduli spaces of curves with polynomial point counts
We prove that the number of curves of a fixed genus g over finite fields is a polynomial function of the size of the field if and only if g is at most 8. Furthermore, we determine for each positive ge...
https://arxiv.org/abs/2410.19913
over 1 year ago
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You too, Politico? No. No! The districts you are talking about are not rural just because they are not in Madison or Milwaukee!
www.politico.com/news/2024/10...
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Have Democrats found a way to win over rural America? Look at what's happening in Wisconsin.
The party’s hot streak in statewide elections faces a crucial test in out-state districts long held by Republicans.
https://www.politico.com/news/2024/10/27/wisconsin-democrats-rural-voters-00185617
over 1 year ago
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Interview with my mom!
cancerhistoryproject.com/article/susa...
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Susan Ellenberg started out as a high school math teacher—then became a leading biostatistician
A mathematical puzzle fascinated Susan Ellenberg as a child. John is twice Mary’s age when John was Mary’s age. When Mary will be John’s age, the sum of their ages will be 63. How old are John
https://cancerhistoryproject.com/article/susan-ellenberg-high-school-teacher-to-leading-biostatistician/
over 1 year ago
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I used to have a car like that
add a skeleton here at some point
over 1 year ago
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Syllabus for Michael Harris's course on mathematics and the humanities:
www.math.columbia.edu/~harris/webs...
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Michael Harris | MATHEMATICS GU4200, Spring 2025 (page under construction)
Professor of Mathematics
https://www.math.columbia.edu/~harris/website/courses1/mathematics-gu4200-spring-2025
over 1 year ago
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Bad headline writing from the Chicago Tribune! The amendment would remove the constitutional guarantee of the right to vote that US citizens in Wisconsin currently enjoy.
www.chicagotribune.com/2024/10/19/w...
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Wisconsin voters consider constitutional amendment barring noncitizens from voting
Republican legislators are asking voters for permission to amend the state constitution to clearly prohibit foreign nationals from voting in any election held in the state.
https://www.chicagotribune.com/2024/10/19/wisconsin-constitutional-amendment/
over 1 year ago
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