[fzliu]

Good catch. I was searching for a game without Nf3, but this is effectively a transposition.

One minor point folks aren't mentioning that I think works in Neimann's favor - Carlsen is known for enjoying the Catalan, and the opening in the game was essentially a Nimzo/Catalan hybrid. This fact makes Neimann's supposed pre-game prep a bit more palatable. Everything else (postgame interview, past history, Twitter antics) seems to work against Neimann though.

My question is - if Neimann did cheat, how? Doesn't seem like something that can be done easily in an OTB tournament.

[eru]

You could stick the computer in your shoe, like the submission suggests?

Or you could swallow a buzzer? The input could come from someone who watches the board from afar?

[whimsicalism]

They metal detected & RF frequency detect before the round 4 match.

[FartyMcFarter]

RF detection before a match seems useless, unless the device is in constant communication.

I don't know enough about those devices and metal detectors to be able to tell whether that's effective mitigation. Could one make a device small enough to be hard to detect?

[lavp]

There are rumors that Carlsen's prep got leaked and that Niemann knew what was going to played the morning of.

Although this is pure speculation, it seems to be a more plausible and satisfactory explanation if Niemann did in fact cheat. It would also explain why Carlsen would withdraw from the tournament rather than continuing.

[mda]

Did Magnus ever played 6.a3 line before in this well known Nimzo variant? The Game with So doesn't have it.