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David Savitt

@savitt

Math professor at Johns Hopkins; board of directors, Canada/USA Mathcamp

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Latest posts by David Savitt @savitt

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Lol, good luck with this one, Parker Executive Search.

15.01.2026 20:49 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

BRB, suddenly feel the need to invent the Sealion Lung.

15.01.2026 04:14 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
King of England on a checkerboard pattern tile floor

King of England on a checkerboard pattern tile floor

Y’all might not appreciate it, but it took him 87 moves and 14 hours to get here

26.12.2025 12:48 πŸ‘ 8710 πŸ” 1288 πŸ’¬ 101 πŸ“Œ 62

Just threw on Juno with my kid and like yep.

23.11.2025 23:11 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Oh for sure, but so often it's so obvious that it takes me home anyway! Bus going by in the background is enough.

And then there's Rumble in the Bronx, but I couldn't find a screenshot that made the point.

23.11.2025 20:48 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I'm from Vancouver, they pretty much all take place there now

23.11.2025 20:27 πŸ‘ 2 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

We had a JetBlue flight for like a minute maybe 15 years ago but it didn't last long.

13.11.2025 16:52 πŸ‘ 3 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0
Fancy Man Enjoys Tea

Fancy Man Enjoys Tea

Fancy Man Enjoys Tea https://theonion.com/fancy-man-enjoys-tea-1819569438/

26.10.2025 15:00 πŸ‘ 1199 πŸ” 95 πŸ’¬ 30 πŸ“Œ 28

Shouldn't the argument where you prove it first for collections of length 2^k by induction on k, and then in general by padding out a sequence of length n by appending 2^k - n copies of the average, just go over almost directly?

26.10.2025 14:05 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I don't get it. Why bother with AI subjects when you could skip directly to having the AI write the paper with fabricated data instead.

09.10.2025 20:22 πŸ‘ 3 πŸ” 1 πŸ’¬ 0 πŸ“Œ 0
Everything Falling Apart, Reports Institute For Somehow Managing To Hold It All Together

Everything Falling Apart, Reports Institute For Somehow Managing To Hold It All Together

Everything Falling Apart, Reports Institute For Somehow Managing To Hold It All Together https://theonion.com/everything-falling-apart-reports-institute-for-somehow-1819569822/

03.10.2025 21:00 πŸ‘ 1399 πŸ” 207 πŸ’¬ 7 πŸ“Œ 7
A screenshot of an article published in popular science. It reads: β€œFirst known wild 'grue jay' hybrid spotted in Texas. Green and blue jays are crossing paths as temperatures rise.”

A screenshot of an article published in popular science. It reads: β€œFirst known wild 'grue jay' hybrid spotted in Texas. Green and blue jays are crossing paths as temperatures rise.”

I’ve been training my whole life for this moment

22.09.2025 05:12 πŸ‘ 412 πŸ” 72 πŸ’¬ 13 πŸ“Œ 22

Best place to wive it wealthily

13.09.2025 01:42 πŸ‘ 3 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0
Post image Post image

Two tweets apart in my timeline.

07.08.2025 18:08 πŸ‘ 1 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Also Sunday evening, Monday morning through evening, Tuesday.....

03.08.2025 18:29 πŸ‘ 1 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

With Tom Lehrer's passing, I suppose this is a moment to share the story of the prank he played on the National Security Agency, and how it went undiscovered for nearly 60 years.

27.07.2025 21:01 πŸ‘ 8660 πŸ” 3614 πŸ’¬ 143 πŸ“Œ 717
Preview
Cosmology Summer Fest 2025 The 2025 Cosmology Summer Fest is in honor of Marc Kamionkowski and Robert Caldwell’s 60th birthdays. The event will be a 2.5-day science workshop during which we will discuss recent progress in a ran...

Enjoying a wonderful conference celebrating the 60th birthdays of cosmologists Marc Kamionkowski and Robert Caldwell. Can't decide which is more impressive, their scientific papers or the amazing family of former students and postdocs.

indico.global/event/14235/...

24.07.2025 14:24 πŸ‘ 41 πŸ” 4 πŸ’¬ 3 πŸ“Œ 0
Dropbox

The notes for the Mathcamp course are here, for anyone interested:
tinyurl.com/p6bvnrwp
In 2 weeks / 10 lectures I made it to the end of section 3, i.e., the level one stuff.

(36/36)

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 0 πŸ“Œ 0

Alright, let me stop here. Thanks for reading to the end. The moral, if there is one, is: thinking about how to explain interesting things to smart high school students is great, and if you have the opportunity, you should do it.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Less surprisingly, the LLMs were quite helpful with proofreading. Gemini especially caught some typos that I'm very glad it caught.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

LLMs do get credit for one trick that made it into the paper, the idea of multiplying by (b/d)^2 in the proof of Lemma 4.9 (though what the LLM suggested was more elaborate and the version in the paper is streamlined).

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

It can often be useful to try to understand why some argument is wrong, and the points on which the LLM was most wrong were exactly the key points. For example the one multiplier system formula I use gives its values on a particular level 24 subgroup.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

They tried to convince me that the multiplier system for eta(z) is trivial on Gamma(24) (false). And later it gave me a beautiful but totally wrong proof of Theorem 4.1 using Gauss sums.

But I would say that each of these mistakes stimulated my own thinking in productive ways.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

... maybe in some dispersed fashion, and LLMs would explain them to me.

What happened was more interesting. I don't think LLMs contributed any ideas to the argument, and they contributed several anti-ideas. They were hard to dissuade from the idea that T and L_N generate Gamma_1(N), for example.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

I want to talk a little bit about my use of LLMs while writing this article. While working on this, I had running conversations going with with Gemini 2.5 Pro and GPT-o3 --- mostly because I expected at the outset that modern treatments of Newman's theorem would already exist...

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

To prove the latter observation, we still require one formula involving the multiplier system for eta. But this formula is elementary in the sense that no Dedekind sums are required either in its statement or its proof. So this is a "Dedekind sum free" proof of the theorem.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

The second observation is that any eta-quotient of integer weight is necessarily modular for some congruence subgroup (with M possibly very large). Newman's theorem follows.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

But these two matrices do NOT generate Gamma_1(N), so why should this condition be sufficient?

One basic observation in today's note is that Gamma_1(N) is generated by T and L_N together with any congruence subgroup (i.e. containing matrices congruent to I mod M for some M).

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

Now, the two conditions in Newman's theorem (the two divisibilities by 24) are precisely the necessary condition that an eta-quotient transform correctly under the two matrices T and L_N:
[ 1 1 ]
[ 0 1 ]
and
[ 1 0 ]
[ N 1 ] .

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0

... to deduce that the multiplier system is trivial on such elements. It all works out, but doesn't seem to explain anything.

23.07.2025 13:18 πŸ‘ 0 πŸ” 0 πŸ’¬ 1 πŸ“Œ 0