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theHigherGeometer

Oh, wow. Just dropped: a 199-page preprint that is claiming a solution of the moving sofa problem!

arxiv.org/abs/2411.19826

cc @johncarlosbaez

9 comments
theHigherGeometer

The optimal shape is the one already known (due to Gerver), but we didn't know it was the shape with the largest area relative to the size of the hallway.

Here's a picture of it moving around the corner

Step by step diagram of Gerver's sofa being slid around a right-angle corner in a hallway.
Tom Lowe

@highergeometer Now somebody just needs to make a sofa that shape.

theHigherGeometer

@Infoseepage
The problem was published in 1966, but is even older than that:

en.wikipedia.org/wiki/Moving_s

Maybe Douglas Adams heard about it, or it's completely reasonable he had the idea independently. Certainly the solution in DGHDA is.... novel! ;-)

@johncarlosbaez

Infoseepage #StopGazaGenocide

@highergeometer @johncarlosbaez Adams apparently stumbled across the similar problem while at St John's Cambridge in the early 1970s. There was a staircase being renovated and furniture was moved into a room at the top of the stair to get it out of the way. After the staircase was finished, the sofas would no longer fit down the stairs no matter how you manipulated them, so the furniture was stuck in those upstairs rooms for decades.

c-x-b :verified: :verified:

@highergeometer there's only one author listed. has this guy just been banging on the sofa problem for years until now

theHigherGeometer

@cxberger As usual, it's almost never a lone genius slaving away. Here's the acknowledgements section of the paper:

Acknowledgements
The author thanks Dan Romik for his thorough support and encouragement that greatly helped the research process. His feedback on the presentation significantly improved the clarity of this work. His package MovingSofas.nb helped making the intricate details of the problem much more accessible to the author. The package was also used to generate figures of Gerver’s sofa in this work.
Acknowledgment is extended to Joseph Gerver and Thomas Hales for their interest in this work and their in-depth discussions. The author also appreciates David Speyer’s efforts in understanding the details and help in refining the presentation. The author thanks Michael Zieve and Joonkyung Lee for their mentorship and valuable advice.
Thanks are also due to Martin Strauss, Jeffrey Lagarias and Alexander Barvinok for their interest, help, and advice during the early stages of the research, as well as to Rolf Schneider for his suggestions on the proof of Theorem 5.2.2. The author acknowledges Hyunuk Nam, Seewoo Lee, Changki Yun, Jacmin Choi, Yeonghyeon Kim, Joonhyung Shin, Yugeun Shim, and Seungwon Park for their interest, discussions, and encouragement.
A prior version of the proof of Theorem 1.1.1 was computer-assisted. [...] The author thanks an anonymous mentor and Hyunuk Nam for their discussions that helped the development of the software.
John Carlos Baez

@highergeometer - nice! I'll check it out. These geometric optimization problems can be fiendishly difficult.

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