I've set up a site called whystartat.xyz. My aim is to collect ambiguous, inconsistent, or just plain unpleasant conventions in mathematical notation.

It's a wiki, so you can edit it. Please add in any examples that come to mind!

An implementation of the Product Structure Theorem for planar graphs, in Python:

github.com/patmorin/lhp

Not exactly industrial-strength, and leans towards simplicity over performance. Still, it can decompose 100k-vertex triangulations in a few seconds. I'm open to feature requests.

I have evolved into my winter form: Shuffling Pile of Blankets

"Letter to AMS Notices: Boycott collaboration with police"

docs.google.com/forms/d/e/1FAI

I support this petition. It presents the issue with sufficient nuance to suggest oversight actions which could reduce bias, while pointing out misuse of 'scientific' basis to cover racism.

Signature on this or a similar petition, and follow-up on its principles, is an available direct action for mathematicians in recognizing the impact of our field on black lives and affirming that yes, .

This is special. This is very special. I had my doubts, but I am convinced. Marvellous. youtube.com/watch?v=yKf9aUIxdb

hey everyone, my PyCon 2020 tutorial session is now online: youtube.com/watch?v=yJ6iN5M42s and contains, well, pretty much everything I know about phonetics, machine learning and meter/rhyme/sound symbolism in poetry. tutorial code and notebooks here: github.com/aparrish/nonsense-v

An enjoyable problem (104.B) from the latest Mathematical Gazette: A regular 7-gon is inscribed in the unit circle, with one vertex at (1,0). Find the equations of the two parabolas, symmetric across the x-axis, which pass through the vertices of the heptagon as shown.

A video animating 99 different unexpected intersection points in various geometric configurations. Probably best viewed with your favorite musical background accompaniment; I suggest a piano trio by Haydn.
youtu.be/jjT3_NMe45I?t=124

I love the mastodon image captioning feature because there are a lot of good uses even for sighted users

- when federation / the other instance / your router fails & the image won't load

- explaining visual jokes while "keeping the medium intact"

- naming a visual symbol you /think/ people will know about but maybe not, so they can look it up & read more about it

- noting 'what to look for' when it's unclear

- translating an image in another language while still letting it speak for itself

Square packing: adamponting.com/square-packing

Adam Ponting found a way to cover arbitrarily large (e.g. as measured by inradius) contiguous patches of the plane by distinct squares of sizes from \(1\) to \((2n+1)^2\), for any \(n\). Via demonstrations.wolfram.com/Pon and mathpuzzle.com/

weird introspective discovery about english count nouns with fractional numbers 

"I have 1 item" — grammatical, unproblematic
"I have 1 items" — ungrammatical, anomalous, I'm making a pull request on this clearly faulty bot
"I have 1.0 item" — hold on this is also bad for some reason?
"I have 1.0 items" — uh not great either but preferable to "1.0 item"

"Scientists give cuttlefish 3D glasses and shrimp films for vision study" theguardian.com/science/2020/j (there's a cute photo of a cuttlefish wearing red/blue stereo glasses, which turns out to work)

Quote: « “A lot of people said it wasn’t going to work,” Wardill said. “They said they’d rip the glasses off. They said there’d be ink in the tank.” »

Translation: "Fools! We showed them all!"

🧵 

I did promise to tell about my BSc thesis topic one day. So get ready for a thread on... fractals! Along the way we'll also meet measure theory, a bit of function theory and several bad jokes.

I'll try to keep this as accessible as possible, even though I'll use some maths terminology. Feel free to ask if something is unclear! If the LaTeX equations do not render correctly for you, try opening the thread on mathstodon.xyz.

This is going to be a long thread, so let's get started!

@fribbledom Indexing your arrays from zero instead of one is what separates us from the animals.

At ICERM this semester, Matthias Goerner made an in-space viewer for hyperbolic 3-manifolds in the geometry/topology software SnapPy starting from our cohomology fractals code. We're still working on it, but here's a path through Dehn surgery space for the fig 8 knot complement.

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