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1:08 AM
Hey, so there's a fact in Scholze's condensed notes that the derived solidification of the reals R is 0. I'm wondering: Is this true for R^discrete as well?
I want to guess that it's not true, but I'm not sure.
 
 
6 hours later…
7:24 AM
@HarryGindi As a discrete abelian group R is just some huge Q-vector space. So the first question is probably understanding what the solidification of Q is
 
 
1 hour later…
8:35 AM
Great point!
Whatever it is, it's not zero.
 
 
2 hours later…
10:20 AM
@RuneHaugseng I'd say both (just to make sure it agrees with what I'm doing)
 
@EdoardoLanari The definition is easy: if $p:C\to D$ is a functor, an arrow $f:x\to y$ in $C$ is cocartesian iff the square $[\operatorname{Map}_C(y,z)\to \operatorname{Map}_C(x,z)]\to [\operatorname{Map}_D(py,pz)\to \operatorname{Map}_D(px,pz)]$ is cartesian. Then $p$ is cocartesian if for every edge $px\to r$ there is a cocartesian lift $x\to \tilde r$ in $C$
(there are a couple of ways of rephrasing the definition, but I'll leave them as an exercise). No idea about a reference though
 
10:39 AM
@DenisNardin Thanks, I am well aware of this formulation. I was looking for the one that is expressed in terms of the existence of a square with invertible horizontal maps towards a "rigid" fibration. I think I saw it somewhere but couldn't find it.
 
maybe definition 2.1 here: arxiv.org/pdf/1702.02681.pdf ?
 
@EdoardoLanari Oh sorry. I don't think I've ever seen the one you're referring to
 

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