Homotopy Theory

5:53 AM

@skd It's supposed to be a rewrite / restructuring of HTT / HA / SAG (or maybe some subset thereof), as far as I know.

But I'm just the tech guy, not the one who actually writes the mathematics.

skd

that's cool. it's a pretty huge project, thanks for helping create it

You can start your own if you want, the software is open source!

But a) it's currently not so easy to use, b) I'm not going to design and maintain it for you :P

user2236

in Mathematics, 7 mins ago, by Perturbative

So question, homology is a functor from the category of topological spaces to abelian groups, but homology also preserves homotopic maps, so can we view homology as a functor from the homotopy category to the category of abelian groups?

6:37 AM

@Pieter I'm pretty sure it's going to be the entirety of those books with only corrections made.

at least that was what I heard

corrections/improvements

Are you saying that you have to rewrite everything by hand?

No, not all. The input is a TeX file and a tags file, and it spits out (the database for) the website.

Also, reorganising thousands of pages of material is not something I'd call "with only corrections made".

You're reorganizing it all?

oof

sounds like a lot of work

I was expecting that it would all be uploaded directly from Jacob's TeX files without any human interaction beyond fixing bugs, and then reorganized/fixed piecemeal over time

like over the next 10 years like the Stacks project has been

No, it won't be a dump in the beginning, and then fixing things over time. It'll be a rewrite from the beginning.

Rough

so that's what's been taking so long

it all makes sense now

Well, that it took so long is because of me, not Jacob :).

6:45 AM

I guess it makes sense to update some of the dated stuff in Jacob's book

a lot of proofs have been simplified and generalized since then

Also the graphics took some time, which is not because of me.

mhm

so is jacob rewriting stuff as well?

or are you sitting in front of HTT and rewriting all of the proofs?

I'm not writing a single line of TeX for this.

Ah, good

oh, I misread

I thought you said "I'm not the tech guy, just the one actually writing mathematics"

lmao, which was the opposite thing

Yeah, the discussion took a confusing turn :).

I'm just an ordinary algebraic geometer, I'm not going to rewrite HTT or anything.

6:51 AM

So one thing I wonder is if there are companies that offer the ability to print books for you if you send them a pdf

What does that have to do with Kerodon or me?

because you could then link up with them and have them do made-to-order books!

There are print-on-demand services, sure.

I think that the book project for HoTT has that set up

that's all!

The whole point of doing things online in a non-book format is that it can grow as you want.

No-one prints the Stacks project (I hope).

Parts of it, sure, that makes some sense.

6:52 AM

I used to print hundred-page chunks to carry around

Yeah, that makes sense, but not all of it.

because at Michigan, we didn't pay for printing at a certain room, for whatever reason

=)

To this day, I'm not sure we were allowed to do it, but we all did it openly, so i dunno

anyway, thanks for the info

Espen Nielsen

9:32 AM

@DylanWilson Is this meant to be a community project? If so how does one contribute?

10:43 AM

@Espen

Sorry, that was too quick

Are you talking about Kerodon?

That is a community project in the sense that everyone can contribute by commenting, but it's not like the Stacks project where everyone can contribute material.

Although it's not if the Stacks project contains so much material which was not written by Johan. But Kerodon is not meant to be contributed to in that way.

Espen Nielsen

11:19 AM

I see.

1:10 PM

@Pieter The kerodon site is really something, thank you so much for your contribution to this project!

not sure if this is the best place to talk about this (basically a formatting issue) but from what i've seen whenever there's a definition the thing that's being defined is in itallic which is good as it distinuishes it from the rest of the text but I would think that making them bold instead would be better. Sorry if this is not an appropriate comment. Feel free to disregard it.

user2236

Also, perhaps add some kind of discussion about the kerodon site at Blog Overflow?

Blog Overflow

Rebecca Chernoff on June 23, 2011

Every Stack Exchange site starts with a Q&A site, made up of three pieces that help bring the whole community together:

bicycles.stackexchange.com, the main Q&A site

meta.bicycles.stackexchange.com, questions about community and administrative matters

chat.bicycles.stackexchange.com, the third place for real-time collaborations

But wait, there’s more?

A couple months ago, the Super User community took it upon themselves to create a blog run by the commu …

To help promote the "community project" aspect.

user2236

1:30 PM

Please disregard the above after I found this

2:15 PM

@SaalHardali We've opted for staying close to whatever happens in the pdf when it comes to emphasis. I think we'll leave it as it is for now. If it really bothers you then you can use a local stylesheet to restyle <em> to be bold.

Yeah I'll probably do that, just thought you might want to have some feedback. I think I understand the reasons to leave it be though. Thanks again!

2:37 PM

@Pieter One more little thing. I have found a couple of very minor typos already and I was wondering whether there's a place where I could record them for you to see. I imagine that given the scale of the project it could help to have an option for arbitrary readers to help with proof reading.

Tom Bachmann

@SaalHardali I would imagine comments would be appropriate for that, but Pieter is the right person to ask obv.

Yup, comments work.

I'm not dealing with typos myself either.

Jacob produces the TeX, and while I could in theory (maybe) change it too I have no intention to do so.

You wouldn't even be the first to point out a typo, Daniel Litt did that yesterday already!

I did notice some silly issues with comment links: comments are on a separate page, but whenever you see a link to a comment it will link to the tag page. I'll fix that soon.

2:52 PM

@Pieter Aha seems I missed the comments feature. Thanks.

Dylan Wilson

7:03 PM

@Pieter I seem to remember at some point on the stacks project being able to see all the tags used to prove a given tag (all the way up the tree, not just one step), but I can’t seem to figure out how to do that on kerodon or the stacks project. Is there a way to do this? (Preferably a way suitable for someone who knows absolutely nothing about computers or programming)

Hey, can you have a 2-category where the underlying 1-category is an actual strict groupoid but you have some noninvertible 2-cells?

@DylanWilson There used to be graphs, visualising the dependencies.

With the new system this functionality was not re-implemented (yet).

I'm thinking like, take a group G, look at BG, and take an element g in G. Then you can map the boundary of the 2-disk into BG sending both 1-cells to g, and you can glue in the 2-disk at g

Is there a name for such a thing?