Effin' itinerant ferromagnetism, this is how it works

January 28, 2019 1:55 PM

Back in the late 1800s, the 15 Puzzle (also known as Game of Fifteen, Gem Puzzle, Boss Puzzle, and Mystic Square) [Wikipedia] "drove the whole world crazy" (perhaps in part because half of the scenarios were unsolvable) [Geeks for Geeks]. Now, this "child's puzzle" helped uncover how magnets really work, as summarized in the title of Marcus Woo's article for Wired. More specifically, Eric Bobrow, Keaton Stubis, and Yi Li recently described Exact results on itinerant ferromagnetism and the 15-puzzle problem [Physical Review B with the abstract; arXiv with the full paper].

If that's all too heady for you and you want to play games, here's the 15 Puzzle online, and Sam Loyd's Cyclopedia of 5000 Puzzles, Tricks, and Conundrums With Answers [Archive.org, 1914 edition] (Sam Loyd's Cyclopedia, previously; plus Sam Loyd's 'Trick Donkeys', previously).

posted by filthy light thief (5 comments total)

“Itinerant ferromagnetism is actually one of the hardest problems in theoretical condensed matter physics,” said Yi Li, a physicist at Johns Hopkins University.

I remember widespread Internet scorn for Insane Clown Posse's question about magnets. I always doubted that the scoffers knew the answer themselves.

...unless they were condensed matter physicists, in which case they probably knew what a devilishly difficult question it was.
posted by clawsoon at 2:18 PM on January 28, 2019 [5 favorites]

Presumably, solving the 15 puzzle is what qualifies one for membership in the Pen Fifteen Club?
posted by Jon_Evil at 2:49 PM on January 28, 2019

Condensed matter physicist here. Nope, laughed at them just as hard as everyone else.
posted by 7segment at 3:03 PM on January 28, 2019 [14 favorites]

I've read the popularisation and still don't understand it.

Is it this: the authors have proved a result in graph theory which shows that spin-up/spin-down electrons traversing certain regular graphs will self-organise into homogenous domains when there is a certain proportion of holes?
posted by Joe in Australia at 5:36 PM on January 28, 2019

I usually use the sliding 15 puzzle to explain what cleaning my office is like, since there is a whole lot of moving things out of the way, so I can move other things out of the way, so I can move other things out of the way, so I can put one away properly -type cascading happening.
posted by rokusan at 8:46 PM on January 28, 2019 [2 favorites]