# Fortnightly links (93)

Martin Kalck, Nebojsa Pavic, Evgeny Shinder: Obstructions to semiorthogonal decompositions for singular threefolds I: K-theory is a really interesting paper, giving obstructions (and exhibiting many examples in natural examples!) to having a Kawamata-style semiorthogonal decomposition for singular varieties. This generalises the case for surfaces, via an interesting relationship between negative K-theory and the Brauer group. Cool stuff.

Qingyuan Jiang: On the Chow theory of projectivization discusses isomorphisms at the level of

*integral*Chow groups arising from semiorthogonal decompositions. The cool thing is that this is usually not what is to be expected from semiorthogonal decompositions, so this is exciting.Kevin Buzzard: Can computers prove theorems? explains how formal proof verification can be considered a game, and actually provides a game-environment for defining the natural numbers!

Do you think we can get the speed running community interested in formalising the proof of Fermat's last theorem? After all, the level has a perfectly good definition, which reads