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Apr 28, 2019 at 14:40 vote accept Tim Campion
Apr 28, 2019 at 6:31 comment added Denis Nardin @TimCampion I guess if you want a pithy saying, obstruction theory is what happens at the border of a fringed spectral sequence (i.e. how you compute differentials in pointed sets). I wish I had something better to say about it, but I'm not aware of a general systematization of fringed spectral sequences, only examples of how to handle particular cases. And obstruction theory for non-principal Postnikov towers fits just fine in the framework, there's a reason I'm not asking $\mathcal{M}_{i+1}\to\mathcal{M}_i$ to be principal fibration.
Apr 28, 2019 at 6:15 history edited Denis Nardin CC BY-SA 4.0
Typos everywhere + better explanation of Bousfield's work
Apr 28, 2019 at 1:08 comment added Tim Campion Thanks Denis, this is great, I will have to dig into Bousfield's paper! So I guess your perspective is that obstruction theory is the study of nice towers (although I suppose classical obstruction theory for non-principal Postnikov towers doesn't quite fit into your framework), and associated to any tower is a (fringed) Bousfield-Kan spectral sequence. So (fringed) spectral sequences actually look more general than obstruction theories in this sense -- I was kind of expecting the reverse!
Apr 27, 2019 at 21:46 history edited Denis Nardin CC BY-SA 4.0
added 13 characters in body
Apr 27, 2019 at 21:39 comment added Denis Nardin All indices probably have off-by-one errors, so handle with care.
Apr 27, 2019 at 21:38 history answered Denis Nardin CC BY-SA 4.0