Ciro Santilli @cirosantilli 40

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PROMYS Europe 2024 problem set / Set 2 / P6 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / P5 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / P4 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / P3 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / P2 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / P1 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / Q2 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe 2024 problem set / Set 2 / Q1 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

Section "Greatest common divisor".

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gmp/antihydra.c by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

Also posted at:

wiki.bbchallenge.org/w/index.php?title=Antihydra&oldid=958 But obviously it got deleted, not even a tiny shitpage maintained by 5 people is immune to deletionism
cstheory.stackexchange.com/questions/20978/what-is-the-smallest-turing-machine-where-it-is-unknown-if-it-halts-or-not/53326#53326
cs.stackexchange.com/questions/59344/what-are-very-short-programs-with-unknown-halting-status/162108#162108

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Antihydra GMP implementation by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe application problem set answers by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

www.reddit.com/r/math/comments/17y9zj3/how_do_i_tackle_problems_from_the_promysross/

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PROMYS Europe 2024 problem set / Set 2 by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

Ciro Santilli got his hands on this one. But he was unable to obtain the others. Solving them here would also pose a serious DMCA risk, so perhaps it's just not worth it.

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Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

The Antihydra is the first hard-looking problem for BB(6), what some would classify as a Collatz-like problem.

It is documented on the Busy Beaver Challenge wiki at: wiki.bbchallenge.org/wiki/Antihydra

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Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

Figure 1.
Toshiba D-088 dental X-ray tube
. Source.

William Coolidge explains medical imaging and X-rays (1940).

Source. Video sponsored by General Electric. A cool insight of this video is that a hot cathode is a more reliable electron source. Previous systems, and presumably including the discovery of X-rays, leftover gas in the tube was used. But this makes things more difficult to control, as we also want to remove as much gas as possible from the vacuum, otherwise electrons collide with the gas and lose energy before hitting the anode.

How Does X ray Tube Works by BiomedEngg

. Source. Describes in particular the rotating cathode method. Interesting observation that this is especially important since the cathode cannot cool quickly due to the vacuum.

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PROMYS Europe 2024 problem set by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe application problem set by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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PROMYS Europe problem set answers by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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Oxford physics past exam paper by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

2010-2016: www.whatdotheyknow.com/request/physics_past_papers_2
2014-2021: www.whatdotheyknow.com/request/oxford_physics_past_papers_2

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Oxford mathematics past exam paper by

Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

www.whatdotheyknow.com/request/maths_papers asked but didn't upload...
www.whatdotheyknow.com/request/oxford_mathematics_prelims_past from 2021 asked for prelims only but no upload

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Ciro Santilli 40 Created 2024-07-12 Updated 2025-07-16

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