JimPropp

I'm delighted to report that I've been chosen to be a Radcliffe Institute Fellow for 2026-2027. I'll spend the year conducting research on tilings and completing a first draft of my book "What Can Numbers Be?: The Further, Stranger Adventures of Plus and Times". https://www.radcliffe.harvard.edu/news-and-ideas/harvard-radcliffe-institute-announces-2026-2027-fellows
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2025-11-21 22:11:08 UTC

Writing in The New Yorker earlier this month, Stephen Witt said matrix multiplication is ugly. Is he right? Check out my take at https://mathenchant.wordpress.com/2025/11/21/is-matrix-multiplication-ugly/
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2025-11-03 23:07:50 UTC

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I wonder how many cell phones lie shattered at the bottom?

2025-09-28 18:52:32 UTC

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Two electrically charged particles (positively or negatively charged) either both experience attraction or both experience repulsion. I would’ve expected the behavior of positive- and negative-mass particles to be similar. What makes gravitational force different? Where does the analogy between electromagnetism and gravity break down?

2025-09-11 11:28:23 UTC

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My basic question is, am I using Mathstodon properly? Sometimes the reactions a post of mine elicits (or rather, fails to elicit) makes me suspect that hardly anyone can see my posts.

2025-08-05 21:19:34 UTC

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The existence of two continued fraction expansions for rational numbers shows up in the failure of Gosper’s c.f. arithmetic algorithms to give the expected answer when you square sqrt(2). More recently it plays a role in the q-deformed real numbers of Morier-Genoud and Ovsienko. But you could argue that the two-faced nature of rationals lurks in the Dedekind cut construction of the reals as well, since each rational number corresponds to two ways to cut the rationals into a down-set and a complementary up-set. Anyway, people who are interested in such things may enjoy my most recent Mathematical Enchantments essay, “When .999… Isn’t 1”: https://mathenchant.wordpress.com/2025/07/17/when-999-isnt-1/

2025-07-23 16:02:08 UTC

I want to support public media in underserved areas of the U.S. Is there a fund that will spend my donation where it will do the most good? https://www.nytimes.com/2025/07/16/opinion/pbs-npr-cuts-funding.html

2025-07-06 17:58:32 UTC

Bought one. Couldn’t finish it.
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2025-06-27 03:11:30 UTC

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Oh good. Perhaps the coming interval of barbarism can be reduced from thirty thousand years to a single thousand?

2025-05-04 20:21:45 UTC

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Wildberger doesn’t go far enough. When we assume 1/3 'exists' in a formula, we’re assuming that the infinite, never-ending decimal .333… is somehow a complete object. Wildberger shouldn’t believe in non-decimal fractions either!

2025-04-05 21:40:16 UTC

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I think I might bring the sign to the Tesla Supercharger station in Lexington, MA later this month and hand out free “I bought this before we knew Elon was crazy” bumper stickers.

2025-04-04 13:21:52 UTC

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I’ll attend the one in Hartford, CR (since there’s an AMS sectional meeting there this weekend at which I’ll be speaking). If anyone else reading this post will be at that rally, look for this sign; I’ll be the guy holding it.
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2025-02-18 02:08:42 UTC

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I was thinking of trying to fit a pun into the piece, but it didn’t make the … well, you know.

2025-02-17 23:01:39 UTC

Richard Dedekind didn't just invent Dedekind cuts (and rings and ideals); he gave us a new way to think about (or avoid thinking about) the ultimate nature of mathematical reality. See "Dedekind's Subtle Knife", this month's Mathematical Enchantment: https://mathenchant.wordpress.com/2025/02/17/dedekinds-subtle-knife/
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