Notices by Christian Lawson-Perfect (christianp@mathstodon.xyz)

When's the last time you typed the character ¬ ?

Why do we use ! instead of ¬ for "not" in most programming languages?

Is there a public list of certificates granted by Let's Encrypt?

Seconds after using certbot to get a certificate on a new domain, which hasn't been linked to from anywhere, I saw requests to URLs like "/.env" and "/.git/config", and I can't think how else someone would think of trying them.

T-shirt idea:

@Infoseepage how did I recognise this as Warkworth only from this photo?! I've only been twice!

Numerologists take note: tomorrow, 27th September 2025, is a square date in both US and Everywhere Else notation.

5205² = 27092025 and 3045² = 9272025

This is the last time this will happen for a thousand years! (except trivial dates where the US and Everywhere Else forms are the same)

(from @EdPeggJr on math-fun)

@anemofilia is this a thing?? My laptop is missing a couple of screws and it never occurred to me to replace them. Where do you get the screws from?

Tried and failed again to use Rust for a quick computationally intensive job.

Stop throwing compilation errors at me! I am a nice boy!!

A few days ago I spent a little bit of time looking at #PeerTube, to see if it can replace YouTube yet.
I tried and failed to set up an instance on my own server, because it doesn't have enough RAM to keep up with transcoding.
I made an account on cuddly.tube: @christianp@cuddly.tube, and had a go at live streaming there but I don't think it kept up. I also uploaded a short video: https://cuddly.tube/w/sMqkvBnzeLk1UtY44nXVeq.

Are there any PeerTube instances that can reliably live stream? I don't mind paying my way in.

(to answer the inevitable question from mathstodon.xyz people: I *could* set up a PeerTube instance linked to mathstodon, but I want to be sure about how much work it is before seriously considering that)

EDIT: aperiodic *tilings*, not aperiodic *tiles*. You can arrange these tiles periodically. That'll teach me to take a second to read an abstract!

Whoah! More aperiodic monotiles! https://arxiv.org/abs/2506.07638

On a MacBook, how are you supposed to discover that Fn+DownArrow is Page Down?

A consultant on Wonderblocks, the cbeebies cartoon that supports the primary coding curriculum, is called Emma Goto.

#NominativeDeterminism

@kline she's got to!

Romania's new president is a mathematician with two gold medals from the IMO.

A proof on every table!

I had an interesting question on colour filter overlays from a librarian today.

A dyslexic student wants to read some original documents, not scans or reproductions, and they'd like to put some colour filter overlays on them.

The librarians are concerned that the documents might get damaged. They want to know if a hand-held colour filter, or something on the light source, would work just as well.

I don't know much about the science of colour filters for dyslexia except I've heard the data on efficacy is mixed, but assuming we want this to happen: is there any strong reason to have the colour filter directly on the document?

I don't know any hashtags that archives people would be watching, so please recommend one if you know one!

#accessibility #dyslexia

The trial of the people accused of cutting down the tree at Sycamore Gap is in progress: https://www.bbc.co.uk/news/live/cvg93k0950pt

They took videos and photos of themselves doing it, which the prosecution have presented. How stupid!

A few mathematicians in the UK have set up the Queer, Equality and Diversity Network for Maths. (Name chosen entirely for the acronym: QED)

https://sites.google.com/view/qednetwork/

"The QED network is a community-led effort by UK mathematicians to connect and support LGBTQIA+ members of the UK mathematics community.

The impetus to set up such a network grew out of the 2024 BAMC conference under a drive for increased UK visibility and community for queer people in the mathematics community."

They're on bluesky at https://bsky.app/profile/qedmathsnetwork.bsky.social. I'll see if I can get them over here too 🤞

When I got a proper stand, Erwin Kreyszig thought he could finally retire after a decade underneath my PC monitor.

But no! I've brought him out of retirement to serve as a counterweight for my 3D printer on this wobbly table.

@julesh and then you have to say "BATMAN!!!" or you can be legally declared dead inside

@julesh don't make me go and look for commits that start with 13