@henryseg@mathstodon.xyz
@henryseg@mathstodon.xyz avatar

henryseg

@henryseg@mathstodon.xyz

Mathematician working mostly in three-dimensional geometry and topology, and mathematical maker/artist working mostly in 3D printing and virtual reality.
#Math #Maths #Art #3DPrinting #Geometry

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henryseg, to random
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What parking space number is under the backpack?

henryseg, to random
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Lots of flat foldable structures with arbitrary cross-sections. @csk @Chaimgoodmanstrauss

henryseg, to random
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Lots of flat foldable structures with arbitrary cross-sections. @csk @Chaimgoodmanstrauss

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henryseg, to random
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The next talk at this workshop (Structures - Polyhedra, Meshes, Platforms, at RICAM in Linz) is “Exploring T-hedral Origami across varied topologies”, by Kiumars Sharifmoghaddam.

henryseg, to random
@henryseg@mathstodon.xyz avatar

Rational six-bar linkage by Daniel Huczala and collaborators. Here's the paper: https://arxiv.org/pdf/2403.00558

A linkage of six bars joined by revolute joints, rotating around a loop of configurations.

henryseg,
@henryseg@mathstodon.xyz avatar

Here's an application in robotics of these kinds of linkages.

A simple robot made out of a four-bar linkage moves a marble up to the top of a marble run.

henryseg, to random
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Nathan Toups interviewed me on his podcast, “Functionally Imperative”. Among other things, we talked about 3D printing, VR, making stuff, the internet, and aphantasia. https://youtu.be/dcS8FjGaOws?si=HmCQr7YQuInP9tVQ

henryseg, to random
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Apologies in advance to the mathematicians who follow this link: https://cims.nyu.edu/~tjl8195/survey/results.html

GerardWestendorp, to random
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I was at the G4G (maths, puzzles, gadgets etc) conference this week. This was one of the “exchange gifts”. I don’t know the creator, if someone knows, please let me know.
It is a torus tiled by 5 squares. I was surprised this is possible, so I figured out a fundamental polygon. This also turns out to be a square, which is possible because ( 5 = 2^2 + 1^2) .

henryseg,
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@oschene @GerardWestendorp Yes, that is her gift exchange.

ProfKinyon, to random
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Student: I get what lemmas and corollaries are, but what's the difference between a theorem and a proposition?

Me: That's a great question. Throughout this term, I've been trying to create a welcoming and supportive atmosphere in the class where everybody can feel comfortable asking questions like that. Your question makes me feel like I've at least partially succeeded.

Student: So you don't know either?

Me (to class): Are there any other questions?

henryseg,
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@ProfKinyon Theorems are fancier than propositions.

henryseg, to random
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"Six axis racks" is a symmetric arrangement of gears and racks. Full video at https://youtu.be/zZdSNUoifV4
#Mechanism #KineticArt

Twelve 3D printed sticks, each with two racks, moves around a core with twelve gears.

DoctorChunder, to random

Hi @henryseg I made a mastodon account just to ask this question: For this cohomology fractal, is there a way to calculate the distance traveled if one were to take an infinitely zigzagging path from A to B to C?

henryseg,
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@DoctorChunder I'm not sure if I understand your question... if you are travelling along the space-filling Cannon-Thurston map to get from A to B to C then I can't think of a way to interpret the question that doesn't give the answer "infinitely far". @saulsch

MotivicKyle, to random
@MotivicKyle@mathstodon.xyz avatar

OEIS may be the only nonempty encyclopedia containing 0% of the subject matter it purports to cover.

henryseg,
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@MotivicKyle At first I thought you were pointing out that it contains no integer sequences at all, because it doesn’t actually list the infinitely many elements of any integer sequence. (Spot the numerous problems with this interpretation!)

johncarlosbaez, (edited ) to random
@johncarlosbaez@mathstodon.xyz avatar

One reason we can't have Trump as president: he operates as a gangster. Today's bomb threat to the judge in his bank fraud trial is just the latest example. Two weeks ago, after the Colorado Supreme Court ruled him ineligible to run for office because of the insurrection he led, they got hit with death threats. And many in the Republican party have fallen in line because of such threats - see below!

People not following the news may not realize how big a problem this is.

It works like this: Trump threatens that judgements against him will cause havoc... and his more unhinged supporters fill in the details. It's called 'stochastic terrorism' - and it's not just chatter. Republican attacks against the Speaker of the House eventually led a guy to break into her house: not finding her, he broke her husband's skull with a hammer. Earlier, right-wingers plotted to kidnap the governor of Michigan, but were stopped by the FBI.

It's horrific. If we don't stop Trump by making him lose this election, we're going to have a mob boss in charge of the USA.

For more details, read on!

(1/n)

https://www.vox.com/23899688/2024-election-republican-primary-death-threats-trump

henryseg,
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@tomruen @johncarlosbaez

“Trump is a menace but I’ll blame Biden and Trump voters if Trump wins.”

That’s not how the function from votes to the outcome of the election works... If we end up with Trump and Biden on the ballot then (third party miracles aside), one of them will win, and only votes for one of them matter. I don’t like it either, but that’s the way the system works at the moment.

henryseg, to random
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Surprised to find out that our Cannon-Thurston carving won a prize in the Mathematical Art Exhibition at the Joint Mathematics Meetings! With @saulsch and Will Segerman.

henryseg,
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Here’s the video we made about these curves if you want to know more:
https://youtu.be/FpeeFcK3lTk

henryseg, to random
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At the Serious recreational mathematics session at the joint mathematics meeting. Persi Diaconis’ train is stuck on the way to San Francisco so Erik Demaine is “improvising”, talking about curved origami.

henryseg,
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Persi made it! His talk is about strategies for playing card solitaire.

aeva, to random
@aeva@mastodon.gamedev.place avatar

"hey aeva what do you do for fun?"

oh, you know, normal things,

henryseg,
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@Atridas @aeva Many of my calculus students still do this - I guess they learned it in high school. Nobody at university level cares about clearing radicals out of the denominator.

henryseg, to random
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Red and Green lasers make for a fractal Christmas tree zoom! Full video at
https://youtu.be/uH8w7I1Og1I

video/mp4

henryseg, (edited ) to random
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Zooming into a 3D printed fractal tree. Full video at https://youtu.be/uH8w7I1Og1I

two_star, to random
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I got mentioned on this Numberphile video that just came out. The funny bit is that they used a photo of me that was taken 18 years ago when I was interviewed for Jason Scott's documentary on text adventures, Get Lamp. Okay, the funny bit about the funny bit is that Scott barely used the footage from the interview. It's not in the main feature at all; there's just a tiny snippet in a DVD extra. https://www.youtube.com/watch?v=3akBMSJ37Uk
The mention of me is at the 9:15 mark.

henryseg,
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@two_star I have no idea where Brady got the photo!

aeva, (edited ) to random
@aeva@mastodon.gamedev.place avatar

#poll

What is the next item in this list:

  1. Translation
  2. Rotation
  3. _
henryseg,
@henryseg@mathstodon.xyz avatar

@aeva Screw motion.

henryseg, to random
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Slide-glide cyclides - a design discovered by Andrew Kepert when investigating ways to “see” why the area of a sphere is four times the area of a disk of the same radius. I added the gears and the base. Full video: https://youtu.be/KD_hRn_97RI

The disk shape.
Midway between the disk and the sphere.
The sphere shape.

henryseg,
@henryseg@mathstodon.xyz avatar

And the files to print out your own version of the mechanism are here: https://www.printables.com/model/651714-slide-glide-cyclides

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