Paul Johnson

@ptwiddle

American mathematician in the UK. Mellowing in middle age. He/Him.

633 Folgt329 Follower475 Posts

Website Bluesky

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Paul Johnson@ptwiddle· Jun 12

Had never noticed this plaque, which leaves out that she moved to Australia a few years later, estranged from her mother Emmeline, and was a founder of the "Australia First" movement, isolationist in World War 2. That famous suffragette-->communist-->fascist pipeline.

Plaque on a pavement, saying "Adela Pankhurst suffragette lived here 1910-1911"

Paul Johnson@ptwiddle· Jun 8

Perks of being a regular: your barista/shop owner flags you down when he sees you passing across the street to foist leftover pastries on you because they're closed tomorrow.

Cardamom knot on a plate with a bite out, a few bags in the background with a chocolate croissant visible

Paul Johnson@ptwiddle· May 20

My 9 y.o. made me a set of Borromean Rings. I feel seen.

A hand holding up a set of Borromean rings made from paper

Paul Johnson@ptwiddle· May 1

An 8 by 8 grid of partitions into distinct parts. No explanation given.

Paul Johnson@ptwiddle· Mar 23

My favorite bit of I94 in North Dakota is the flat as a pancake continental divide. Bismarck is on the Missouri river which flows I to the Mississippi and down to the Gulf of Mexico; Fargo is on the Red River which flows North into Hudson Bay. But it's just great plain between them.

Road side saying there's a continental divide; but it's the middle of a flat green field and not the "expected" mountain.

Paul Johnson@ptwiddle· Jan 31

Two mutuals in a row doing it with the same bit I was using, so I'll tweak it and do five undergrad courses where we just read a single book: 1. Structure and Interpretation of Computer Programs 2. Tristram Shandy 3. Pale Fire 4. Ulysses 5. Three-Dimensional Geometry and Topology

Two bsky posts from mathematicians, doing the "5 courses you took as an undergrad" meme, with the first four of each being mostly liberal arts courses and the last one being differential geometry.

Paul Johnson@ptwiddle· Jan 20

The smallest hint of colour.

Grey high rise hospital on a grey day. One window has pink and blue colour frames and yellow and green blocks of colour

Paul Johnson@ptwiddle· Dec 18

Poster of "The Lovers" Tarot card art with a furby flipping the bird as a priest? And Mr. and Mrs. Blobby as the lovers. Your guess is as good as mine.

Paul Johnson@ptwiddle· Dec 16

Leaving work *before 4:30* to play dad taxi and it's already basically dark. Bring on the longer days already....

View of an urban sunset. Children's hospital with lots of bright lights in foreground

Paul Johnson@ptwiddle· Sep 11

Finally getting around to reading @essj.bsky.social's Darryl after seeing I think @jsellenberg.bsky.social talk about it ages ago? Anyway, it's great, Darryl's voice is :chef's kiss:, and *of course* he's a Lebowski guy. It's made me pull Berryman's Dream Songs down off my shelf.

A paragraph from Jackie Ess's Darryl:

Satori is such a perfect woman that she makes a man even out of me. I am a man. But my manhood is like a hothouse flower, not of our climate. Delicate, but real. I feel strong. There's a Bob Dylan song where he says, "Take a woman like your kind to find the man in me.' So is 'your kind' a slightly hippie goth aesthetic in a spiritually realized poly chick? He probably meant a different kinda I think that's why the song works though, it's nothing to do with types. But the song totally inhabits a moment, the guy singing it does t know that yet. I never really liked Bob Dylan, it always felt like he was lecturing me or trying to get me to be a Christian or something, but I heard that song in a movie once, and it made me go back to his stuff.

Paul Johnson@ptwiddle· Sep 2

Last day of summer vibes.

Squirrel sprawled out on its belly in the sun at the peak of a tiled roof.

Paul Johnson@ptwiddle· Aug 5

Written out quickly and a bit ugly...

Messy handwritten proof using similar triangles

Paul Johnson@ptwiddle· Jul 1

Late to the sign meme, but loved this bit of guerilla activism at an intersection close to @sheffielduni.bsky.social that really needs a pedestrian crossing. Just walked by it this morning and the sign has been taken down.

Picture of an official looking sign saying "PEDESTRIANS GOOD LUCK" attached to a lamppost in front of a busy intersection.

Paul Johnson@ptwiddle· Jun 28

Thanks! Here's the people who will be streaming by you in an hour or two.

Paul Johnson@ptwiddle· Jun 27

Just finished session Zero of Slugblaster by @wilkiescandylab.com with @thebadspot.bsky.social , @jenduckie.bsky.social @andrewwormald.bsky.social. Excited for first session, and not just because the endpaper is the 15th and final pentagonal tiling to be found. (And a tiny K-Theory reference...)

Picture of the 15th pentagonal tiling, white lines on black paper)

Paul Johnson@ptwiddle· Jun 7

First learned about ginger congee when reading The Year of Magical Thinking, and didn't really know what it was but it's comforting powers stuck with me, I made it once, and now it's a go-to. Any food you love that you've learned from a boo/song/ someplace you couldn't see/smell it first?

Bowl of rice porridge with cilantro, pumpkin seeds, and green onion on top, next to some broccoli on a plate.

Paul Johnson@ptwiddle· Dec 21

Birthday books! "Oh, I follow @antonhur.com on Bluesky!" Scotch and chocolates and socks not pictured.

Two books on a table. Black Paper by Teju Cole, and Toward Eternity by Anton Hur.

Paul Johnson@ptwiddle· Dec 19

How about some roses? (is a rose is a rose is a rose)

Snipper from Culler and Vogtmann's Moduli of Graphs and Automorphisms of Free Groups. Starting in Section 1.3 Roses, it states the Gertrude Stein Lemma.

Paul Johnson@ptwiddle· Dec 16

This immediately brought up Thurston's "On Proof and Progress in Mathematics" arxiv.org/abs/math/940...

This question brings to the fore something that is fundamental and pervasive:
that what we are doing is finding ways for people to understand and think about
mathematics.
The rapid advance of computers has helped dramatize this point, because computers and people are very different. For instance, when Appel and Haken completed a proof of the 4-color map theorem using a massive automatic computation,
it evoked much controversy. I interpret the controversy as having little to do with
doubt people had as to the veracity of the theorem or the correctness of the proof.
Rather, it reflected a continuing desire for human understanding of a proof, in
addition to knowledge that the theorem is true.
On a more everyday level, it is common for people first starting to grapple with
computers to make large-scale computations of things they might have done on a
smaller scale by hand. They might print out a table of the first 10,000 primes,
only to find that their printout isn’t something they really wanted after all. They
discover by this kind of experience that what they really want is usually not some
collection of “answers”—what they want is understanding.

Paul Johnson@ptwiddle· Dec 8

TFW you're exploring on your long run and only vaguely know where you are and stumble across the outdoor market with the good coffee.

Selfie of bearded man (me!) in running gear, holding a paper espresso cup, in front of small green van with "Motore Cafe" written on it. Nether Edge market, Sheffield.

Paul Johnson@ptwiddle· Dec 7

I thought everyone had their own copy? (I think mine was around twenty pounds from the massive Sainsbury's).

A hand holding a copy of the Borromean Rings made out of wood: three loops so that are interlocked in such a way that they can't be separated, but if any one loop was removed, the other two could be separated.

Paul Johnson@ptwiddle· Dec 3

Somebody was thrilled to be watching the Lionesses.

View at a football match. Looking over the shoulder of a young girl as she reads a novel, green of the pitch, bright lights and the crowd in the background.

Paul Johnson@ptwiddle· Nov 24

Fun on my run!

A stone staircase outside, turned into a waterfall.

Paul Johnson@ptwiddle· Nov 19

Today's run was more of a sanity jog, stopping to just enjoy the rare snow.

Snowy forest scene, path along an old mill wall, mill run on the left and the river Rivelin on the right.

Paul Johnson@ptwiddle· Nov 18

In happier news:

Blurry shot of snow falling in streetlight in front of stone building

Paul Johnson@ptwiddle· Nov 18

Of course that counts. If you want it not to count switch it to your kid being a bat on Halloween this year (mask handmade by her elder sister).

Not a birb, but a bat -- a child in a narrow brick alley trick or treating in a bat costume.

Paul Johnson@ptwiddle· Nov 15

One last coffee in the park before the cold snap hits.

Weston Park in Sheffield. Modernist building Arts Tower in the background, teal bandstand, one large tree with just a few leaves hanging on still and a carpet of them spread beneath.

Paul Johnson@ptwiddle· Nov 14

It's the leave work early to still have a little light on the walk home time of year.