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Dave Richeson

@divbyzero.bsky.social

1.8K followers 500 following 11K posts

Mathematician. John J. & Ann Curley Chair in Liberal Arts at Dickinson College. Author of Tales of Impossibility and Euler's Gem. Coffee drinker. [Everything in the timeline before October 2024 was imported from my Twitter/X feed 2008-24.]

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Dave Richeson @divbyzero.bsky.social · Oct 21

Since I'm new here, I'll introduce myself. I'm a math prof at Dickinson College. I'm author of Euler's Gem and Tales of Impossibility. I was editor of Math Horizons. I am interested in topology, dynamical systems, geometry, history of math, recreational math, math & art, and expository math writing.

Dave Richeson @divbyzero.bsky.social · 16m

Very nice! If you follow the link to Want and Zhang's preprint, here's the figures they gave.

Reposted by Dave Richeson

Dave Richeson @divbyzero.bsky.social · 13h

New blog post! Through a sequence of images, I verify that the unknotting number of the connected sum of a (2,7) torus knot and its mirror is less than 6: I show that this first image is the connected sum, and after changing those crossings, it produces the unknot! divisbyzero.com/2025/10/08/t...

A drawing of the connected sum of a (2,7) torus knot and its mirror image (much modified).

An image of a crazy knot I claim is the unknot.

Dave Richeson @divbyzero.bsky.social · 4h

That works! I thought of it as flipping over the bottom knot and then running the string around the top one.

Dave Richeson @divbyzero.bsky.social · 13h

Fact: this took me a week. I kept coming back to it, fixing mistake after mistake after mistake!

Dave Richeson @divbyzero.bsky.social · 13h

New blog post! Through a sequence of images, I verify that the unknotting number of the connected sum of a (2,7) torus knot and its mirror is less than 6: I show that this first image is the connected sum, and after changing those crossings, it produces the unknot! divisbyzero.com/2025/10/08/t...

A drawing of the connected sum of a (2,7) torus knot and its mirror image (much modified).

An image of a crazy knot I claim is the unknot.

Dave Richeson @divbyzero.bsky.social · 9d

That's nice. Thanks! Goodness knows, they've seen me make typos in class and on their assignments.

Dave Richeson @divbyzero.bsky.social · 9d

There's that!! 😂

Dave Richeson @divbyzero.bsky.social · 10d

That's definitely a good rule for everyone!

Dave Richeson @divbyzero.bsky.social · 10d

It works! Cool. THanks for the link

Dave Richeson @divbyzero.bsky.social · 10d

the AI write it for you.
• Show respect to the person you are writing to—address them appropriately, use proper punctuation and capitalization, etc. But do not stress out about it if it is not perfect. It is just an email!
• You can always talk to me in person!

What else would you suggest?

Dave Richeson @divbyzero.bsky.social · 10d

times when they've asked me for help writing an email or proofreading something they've written.

I'm going to tell my students:
• Write it yourself. We want to hear your voice in your email.
• You can ask AI for suggestions about what or how to write the email if you want to, but don't have

Dave Richeson @divbyzero.bsky.social · 10d

perfectly boring and lacking in humanity. "I hope this email finds you well. Unfortunately, I am feeling under the weather..."

Having college-aged kids of my own, I know that corresponding with professors and other authority figures in writing is challenging for them. There have been countless

Dave Richeson @divbyzero.bsky.social · 10d

I'm going to chat with my students about email.

A few years ago, we would complain that student emails read like text messages to their friends—ultra informal, all lowercase, etc. "yo prof what sections is the exam on"

Now, we've swung in the opposite direction. They are written by AI. They are

Dave Richeson @divbyzero.bsky.social · 11d

you is wrong. The problem is, we don't know which 50%."

Dave Richeson @divbyzero.bsky.social · 11d

Where does survey design fall on this list?

A better question: In a class about X, what percentage of info you're taught is true, correct, or will still be believed 20 years from now? Math would do pretty well.

My dad taught med school and told his students, "50% of what we will teach

Dave Richeson @divbyzero.bsky.social · 13d

work. Approximately half of the people we surveyed viewed colleagues who sent workslop as less creative, capable, and reliable than they did before receiving the output. Forty-two percent saw them as less trustworthy, and 37% saw that colleague as less intelligent."

Dave Richeson @divbyzero.bsky.social · 13d

"We define workslop as AI generated work content that masquerades as good work, but lacks the substance to meaningfully advance a given task."

"The most alarming cost may be interpersonal. Low effort, unhelpful AI generated work is having a significant impact on collaboration at

AI-Generated “Workslop” Is Destroying Productivity

Despite a surge in generative AI use across workplaces, most companies are seeing little measurable ROI. One possible reason is because AI tools are being used to produce “workslop”—content that appea...

Dave Richeson @divbyzero.bsky.social · 18d

Interesting. I don't know that game. It looks like the game consists of more than just the dice, though. So, it would be weird to include just the dice in the gift bag (?).

Dave Richeson @divbyzero.bsky.social · 18d

1: red
2, 3, 4: white
5, 6: black

Dave Richeson @divbyzero.bsky.social · 18d

We got a bag of goodies this summer at the MoMath MOVES conference. It contained these three dice with colored pips. Does anyone know if they come from a game of some sort? They were just in there by themselves.

Dave Richeson @divbyzero.bsky.social · 18d

My colleague sent this to me.

A ∩ Aᶜ ≠ ø ?

🤣🤣🤣

Dave Richeson @divbyzero.bsky.social · 19d

Dave Richeson @divbyzero.bsky.social · 19d

Dave Richeson @divbyzero.bsky.social · 19d

do. Each post below has two screenshots of the faces and the original image. Note: if you tap on the face, the hands and the rest of the face become very faint, and you can turn the dial to see the kaleidoscope effect. That's what these screenshots are of.

Dave Richeson @divbyzero.bsky.social · 19d

I decided to change my Apple Watch face. I'd never tried the Kaleidoscope face, but it is fun to play with. After using some photos from my Photos app, I made a few images in Illustrator to use with the face. Here are some examples. Obviously, there is a lot more you can