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Gregor

@coexact.bsky.social
242 followers 476 following 1.9K posts

only made of atoms

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Reposted by Gregor
Gregor @coexact.bsky.social · 30/08/2026
let me try to explain. As everyone knows from kindergarten, a massless fermion comes with a definite chirality and a mass term for a fermion is a bilinear coupling between two such of opposite chiralities (a Majorana is the special case where they are each others antiparticle).
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Gregor @coexact.bsky.social · 27/07/2026
Page & Wootters:
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Gregor @coexact.bsky.social · 13/06/2026
random matrix models.... 🫨
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Gregor @coexact.bsky.social · 28/05/2026
This is a nice discussion with points that I am largely sympathetic to. I have some thoughts on the conclusions drawn at the end about the emergence of time—though these matters are so uncertain that it's impossible for me to have any tightly-held conviction. Nevertheless:
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Gregor @coexact.bsky.social · 28/05/2026
still dropping bangers!
youtube.com
Holograms and their Standard Models: DSSYK_∞ and the ‘t Hooft Model - Leonard Susskind
YouTube video by Institute for Advanced Study
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Gregor @coexact.bsky.social · 10/05/2026
I wrote a blog post about quantum reference frames, energy conservation and also gravity
coexactly.github.io
Keeping Time and Energy in Closed Systems
Clocks, energy, and the problem of time in closed quantum systems.
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Gregor @coexact.bsky.social · 16/04/2026
The existence of reginos implies the existence of their supersymmetric partners: regions
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Gregor @coexact.bsky.social · 05/04/2026
thread with random things found in my grandparents' apartment. A distorted mirror
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Gregor @coexact.bsky.social · 05/04/2026
it's cool that 'gravity is non-local magic' seems to be an accurate description according to the state of the art
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Gregor @coexact.bsky.social · 05/04/2026
this plant grows orbifolds (the conical thing)
calathea orbifolia, a plant with a conical leaf
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Reposted by Gregor
QuOI Theory @quoi-theory.at · 01/04/2026
A new, very serious preprint is out from Veronika and Alberto. No, don't look at today's date it's 100% legit we promise. It's a genuine proof that P=NP... (...if you believe in quantum many-worlds and are willing to destroy almost every observer in the multiverse 👀) arxiv.org/abs/2603.28869
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Gregor @coexact.bsky.social · 26/03/2026
this fact is my downfall—my pathology is I will still tag myself ':)'
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Gregor @coexact.bsky.social · 11/03/2026
received a blessing—
arXiv bot (math-ph) liked your post
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Reposted by Gregor
Sophie Huiberts @sophie.huiberts.me · 03/03/2026
It's been almost two years and still I hear of people calling my IPCO lecture a scandal 😊
youtu.be
Open Problems & Diet Problems
YouTube video by Sophie Huiberts
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Gregor @coexact.bsky.social · 26/02/2026
Can anyone make a carpet with this pattern?
Adams spectral sequence
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Gregor @coexact.bsky.social · 21/02/2026
so I just realized the very obvious fact that if I can apply a noise removal filter to my mic input in calls, I can also apply it to any other audio stream and poorly recorded video lectures just got so much more pleasant
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Gregor @coexact.bsky.social · 21/02/2026
uranus is having a y2k-aero phase 🙄
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Gregor @coexact.bsky.social · 13/02/2026
advice from Dirac for whoever needs it
It is a bottomless sea, but we do not have to worry about that. The picture of a bottomless sea is not so disturhing really . We just have to think of the situation near the surface,
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Gregor @coexact.bsky.social · 08/02/2026
this is what we have the renormalization group for Goku is just at a critical point
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Reposted by Gregor
4gravitons.bsky.social @4gravitons.bsky.social · 05/02/2026
Physicists of Bluesky! I'm looking for a specific type of story from the early days of cyclotron research, for a piece for @physicstoday.bsky.social . Have you heard tales of scientists who aligned beams with the naked eye? Know an older physicists who has? Let me know!
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Gregor @coexact.bsky.social · 04/02/2026
for those unaware, this feed is extremely cool & useful & good!
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Gregor @coexact.bsky.social · 29/01/2026
You've heard of Solomon Lefschetz, but did you know he had an evil twin? We just call him perverse weak Lefschetz, he proved the perverse weak Lefschetz theorem
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Reposted by Gregor
Gro-Tsen @gro-tsen.bsky.social · 13/01/2026
Here's a mathematical fact which I find amazingly counter-intuitive: There exists a polytope (=the convex hull of a finite set) in ℝ⁴ which is not combinatorially equivalent to one with rational vertex coordinates (=the convex hull of a finite subset of ℚ⁴)! 🤯 •1/4
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Reposted by Gregor
Sarah Z @sarahz.bsky.social · 06/01/2026
In a strange position where I think there are massive, massive social harms to the proliferation of AI (misinfo, deepfakes, predatory 'companions', surveillance, labour rights) but also feel the mainstream arguments against it range from unconvincing (water) to actively harmful (copyright; "soul")
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Gregor @coexact.bsky.social · 23/12/2025
kinda interesting story here. Can a LLM with some vibecoded framing produce a decent index for a book? I confess I wasn't aware of indexing as a profession prior to this, but even without leaving this site you can find the tail end of a community, with orgs, conferences, meetups..
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Gregor @coexact.bsky.social · 22/12/2025
no matter how you slice it, if intelligent life survives all other hurdles, it will eventually end for astrophysical reasons, be that the expansion of the sun or cosmic heat death. It will be like climate change but worse: much slower, much more predictable, not preventable, hopelessly unsurvivable
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Gregor @coexact.bsky.social · 22/12/2025
to point at an elephant, it is incredibly obvious that the long-term global "cost" of basically ending extreme poverty is super-duper negative
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Gregor @coexact.bsky.social · 22/12/2025
Have known the evenings, mornings, afternoons, I have measured out my life with coffee spoons (TS Eliot) (The power was out at the NIST atomic clocks, presumably)
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Gregor @coexact.bsky.social · 17/10/2025
If you've ever wanted to actually watch a laser beam bounce through a light clock, AlphaPhoenix just dropped the most incredible video
youtube.com
This is what the speed of light looks like
YouTube video by AlphaPhoenix
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Reposted by Gregor
Craig Gidney @craiggidney.bsky.social · 31/08/2025
Been awhile since I wrote a blog post. Anyways... why haven't quantum computers factored 21 yet? algassert.com/post/2500
algassert.com
Why haven't quantum computers factored 21 yet?
Craig Gidney's computer science blog
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Reposted by Gregor
🇵🇸Tim Henke (tɪm 'ɦɛŋ.kə) @timhenke.bsky.social · 13/08/2025
THREAD: Resurgence or: How do physicists keep getting away with ignoring infinitely big things? I wrote about this back when everyone was still on twitter. Someone asked me a question and I think it's an excellent occasion to repost the thread. 1/20
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Gregor @coexact.bsky.social · 03/08/2025
obsessed with this prediction of 2025 by a 1999 4th-grader; I've read it so many times and it's complete poetry
The Predictions

I think life in 2025 would be really scary. Cars would be flying in the air. Planes will be flying on the ground. Cows will be flying int he air. There will be man-eating plants and man-eating beds. Man-eating footballs, pencils and baseballs. There would be aliens that would say MOO MOW. There will be cows that run around in circles like they are dumb. Cats will be 1 centimeter long. Cars will be flying on the ground. Houses will be haunted by ants and it will be scary.

Andrew Baratucci

Fourth Grade 

Paxtonia Elementary School
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Gregor @coexact.bsky.social · 16/07/2025
Natural bundles are those associated to the frame bundle; spinor bundles are supernatural
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Gregor @coexact.bsky.social · 16/07/2025
Kids these days... built different
Google search result titled "D-modules and microlocal calculus" with description "This textbook for the undergraduate vector calculus course presents a unified treatment of vector and geometric calculus."
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Gregor @coexact.bsky.social · 04/07/2025
Is it just me or is user-restricted search broken?
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Gregor @coexact.bsky.social · 30/06/2025
I've had enough summer now we can skip the rest
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Gregor @coexact.bsky.social · 25/06/2025
this was accidentaly a question about eternal inflation
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Gregor @coexact.bsky.social · 20/06/2025
thought about this again recently and have a picture I'm satisfied with, I think. Suppose at some spacetime pt there is a spontaneous nucleation of a decay to a new Lorentz-symmetric vacuum. This spreads out in a bubble at the speed of light and inside the bubble there must be some hot state to
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Gregor @coexact.bsky.social · 06/06/2025
did uall know they found a geometric circle in the sky
screenshot out of https://arxiv.org/abs/2505.04041; a perfect circle in an astronomical photo
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Gregor @coexact.bsky.social · 02/06/2025
one day I will complete a second blog post
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Gregor @coexact.bsky.social · 31/05/2025
Aaron Swartz should Also have been granted unfettered access to JSTOR tbc. Weird twisting going on here. Pls don't go to bat for academic publishers bc you don't like AI
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Gregor @coexact.bsky.social · 26/05/2025
lmao at one pt the startup CEO guy says that soon datacenters will cause '10-15 degrees of global warming', not bc of fossil fuels but bc they just pump out heat by themselves guess we've found the magical energy source of the future: datacenters
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Gregor @coexact.bsky.social · 20/05/2025
I am apparently just going to be miserable & stressed this week until I manage to Do the Task
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Gregor @coexact.bsky.social · 19/05/2025
my apartment has been getting cleaner today, which is unrelated to the hypothetical existence of any pressing unpleasant tasks that I could be taking care of
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Gregor @coexact.bsky.social · 17/05/2025
just went to the optician and it turns out my vision has worsened by a full diopter in the last year oops
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Gregor @coexact.bsky.social · 12/05/2025
learning things on wikipedia
Etymology
Gamergate derives from the Greek words γάμος (gámos) and ἐργάτης (ergátēs) and means 'married worker'. It was coined in 1983 by geneticist William Louis Brown[1] and
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Gregor @coexact.bsky.social · 09/05/2025
I've always nodded through the stimulated emission part of how lasers work but it's actually a bit strange huh
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Gregor @coexact.bsky.social · 03/05/2025
Anyone know exactly how these images depict elliptic curve isogenies? Apparently the sixth one is inseparable but what precisely am I looking at?
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Gregor @coexact.bsky.social · 29/04/2025
A sphere? oh you mean a Euclidean de Sitter space?
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Gregor @coexact.bsky.social · 13/04/2025
this is what a global field of positive characteristic looks like btw
sketch of a mapping torus of a genus 2 surface, fibered in the obvious way over a circle labeled Spec F. An embedded double covering of the circle is labeled 'rational point of degree 2'. the two intersections of this curve with a fiber are labeled x and Frob x
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