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00:00
Where the set of maps {A,...,A,M}-->M is {linear orders of {A,...,A,M} in which M is maximal}.
(Note, this is not the way Lurie does it, in particular, he doesn't state the symmetric group actions explicitly)
1.5.1 of this paper arxiv.org/pdf/math/0512576v2.pdf seems to indicate that the set of multimaps {A,...,A,M}-->M should be the same as the set of multimaps {A,...,A}-->A (assuming the domains there have the same number of elements) but this cannot be true?
00:22
Hm but actually that description is given elsewhere as well.... hrmmmm.
00:36
Ah... but that must give you bimodules.
Hmmmm, so I dunno the action should be then.
 
1 hour later…
01:49
The symmetric group does not act on the set of maps {A,...,A,M}->M. Rather, it acts on such a map by producing a new map {A,...,M,...,A}->M, where the elements of the n-tuple have been permuted by your permutation. (For a 1-colored operad, you only see a symmetric group action of course.) As for how this action works, it ends up being tautological, since the maps {A,...,M,...,A}->M correspond by definition to the ways to multiply the coordinates in any order, as long as the rightmost one is M.
Well now I am a little confused... It seems like the LMod that Lurie defines in HA 4.2.1.6 is a nonsymmetric operad, because he doesn't allow the kind of permutation of {A,...,A,M} that I just described.
So I think that LMod as defined in 4.2.1.6 is a nonsymmetric operad, but in order to make it symmetric, you have to include as part of the data total orderings on each fiber, as in 4.1.1.1, which would make my original answer valid. Maybe this is a typo?
02:30
@JohnBerman so I think a group action on a set is the same as saying "the group acts on an element of the set by taking it to another element" right?
I mean, that set on the left-hand side isn't ordered.
Okay, I see what you're saying.
Yeah, I mean, I should have written $Mul(\{X_i\}_{i\in I},X)$ such that $X_i=M$ for exactly one $I$ and $X=M$.
@JohnBerman I'm pretty sure every operad in HA, by virtue of partaking in a cocartesian fibration down to Fin_*, is symmetric.
Including $Ass^\otimes$.
But at least in the infinity operad story, {A,...,A,M} and {A,...,M,...,A} refer to different objects of the infinity operad. They are equivalent, but in order to specify an equivalence, you need to pick a permutation that permutes one into the other.
Fwiw, I was more interested in just the colored operad story. But let me see if I can understand what you're saying.
I think the issue here is that {A,...,M,...,A} should not be coming up at all, since we only want A to act from the left.
Ass^\otimes is definitely symmetric, but only because the data of a map {A,...,A}->A actually includes a total ordering on [n]
The case you're describing is more the case of bimodules, I think.
Likewise, I claim the data of a map {A,...,A,M}->M should include the data of a total ordering on {A,...,A,M} for which M is maximal in the ordering
02:36
Yeah of course.
But the symmetric group should only be permuting the A's, not the M.
I really think it permutes the whole thing, but it also permutes the chosen total ordering in such a way that they cancel out
Hm.... I think my problem with that is that the indexing set that Lurie uses is not ordered.
This is how Ass works, anyway
I.e. he writes {X_i}_{i\in I}
Not {X_1,X_2,...,X_n}
Exactly! But in 4.2.1.6, he acts like he has chosen an ordering. That's why I say there must be a typo.
02:39
Hmmmmm, interesting.
4.2.1.1 says that the morphisms in LMod do choose an ordering
What he seems to be describing is a nonsymmetric operad, in which case Fin_* would be replaced by totally ordered finite sets, but I think this can be corrected the same way he built Ass
I mean, abstractly it makes sense to talk about "linear orderings on the unordered set {A,...,A,M} such that M is maximal"
Ultimately I'd really like to know how operad theorists did this before Lurie. He obscures a lot of stuff.
@TylerLawson You're right! I was just getting confused because I skipped to 4.2.1.6.
Okay, then I will shut up, but I assume the answer would be the same...
Well, I mean no it's fine... I just think that it would be helpful to understand 4.1.1.1, this LM object.
Like, all of Lurie's "colored operads" are the same thing as symmetric multicategories, or symmetric colored operads, or whatever. Things for which there is a $\Sigma_n$-action on the sets of multimaps.
And I'm trying to see how to interpret LM in this way.
02:48
But again, when you apply a permutation to {A,...,A,M}->M, you get a map {A,...,M,...,A}->M
Regardless of the location of M in the tuple, the set of maps {A,...,M,...,A}->M is the set of total orderings for which M is maximal
so when you apply the permutation, you permute the tuple, but permute the total ordering in the same way, so that you have effectively done nothing
Hm, ok, that makes sense.
Let's see then... this should probably be able to be produced by taking a planar version of LM and symmetrizing it.
Yeah I think what we are seeing is that there is an underlying nonsymmetric operad
Right, that seems to be what happens when you symmetrize, you basically get a bunch of meaningless permutations.
which is not surprising, since LM should be able to apply to (not necessarily symmetric) monoidal categories
So, okay... planar LM should have two objects (A,M).... a unique map (A^n,M)-->M and a unique map (A^n)--->A, for all n, and no other maps (except identities)
02:53
I think the last M should be an A
Whups, yeah.
God, yeah, this would be a lot easier if I just indexed over only finite ordinals... instead of arbitrary finite sets.
Ah ok, and then when we symmetrize we get this one unique map moved all over the place
and we take the coproduct over all these moves
But, as you say, the "map" basically undoes the permutation first, then applies that one unique map.
I'm actually looking at page 36 (PDF page 46) of this Masters thesis of Trova. Pretty nice. math.leidenuniv.nl/scripties/MasterTrova.pdf
yikes, it's a little too late for me to think about that
Haha wait really? It's just what you've been saying right?
I guess I was referring to the dendroidal set part
Oh lord. Yeah. No no, I'm just talking about the intro stuff. =P
03:03
I should really go, though; glad I could redeem myself
Hah, alright cya.
Actually, ugh, for Lurie Fin_* IS just finite ordinals (with a base point).
03:27
@JonBeardsley if you're wanting to index over finite ordered sets and order-preserving maps, this is roughly what all that stuff about "approximations" does (doing things for "ordered sets and ordered maps" is enough instead of doing it for "finite based sets" and "maps with a linear ordering on fibers"). for algebras this is 4.1.2.10 and for algebra-module pairs this happens somewhere around ... 4.2.2.8?
this is why sometimes LMod and sometimes Δ-LMod shows up
@TylerLawson right right but that wouldn't work for symmetric stuff, I more mean that Lurie defines colored operads as having maps {X_i}_{i\in I}-->X for every finite set I, but if you look at the construction passing from O to O^\otimes, he only bothers with the ones where I is {1,...,n}
I definitely don't want to work over order preserving maps.
no, certainly not, that only works for the planar operads that map to the associative one
In other words, if you look at the classical literature, the multimaps always go (X_1,...,X_n)-->X, rather than this more general indexing over every finite set.
It's a really dumb point, but it seems unnecessary to use this language at all.
well, right, that comes up in the classical case too when you do nonsymmetric vs symmetric
(the construction I'm talking about is 2.1.1.7, by the way)
03:33
i guess the point is that the distinction is between whether you have multimaps (X_1,...,X_n) -> X or {X_1,...,X_n} -> X
i.e. whether your source has a chosen ordering or not
Right.
Hm.
the general framework, because it allows symmetries, works with the latter, and you need the "approximation" stuff to show that the former is equivalent in the nonsymmetric case
But I'm not sure I follow, b/c if you look at, say, the definition of colored operad in this paper of Berger-Moerdijk, arxiv.org/pdf/math/0512576v2.pdf, (on page 3) they index over the natural numbers.
And they add in the symmetric group action as additional data.
So it seems like you could do the same thing (basically) by indexing over the category of sets {1,...,n} and ALL functions between them.
Rather than all finite sets and all functions between them.
I.e. have multimap sets Mul({X_i}_{1<=i<=n},X) for all n.
I'm not sure I follow.
Definition 2.1.1.1 of HA says that a colored operad says that you have this set Mul(...) for every finite set I.
I think the point I'm making is just so trivial.
03:48
Ah, yeah, those categories are equivalent and so you should be able to use either.
Right.
That was all. Nothing really relevant to the actual structure of anything.
04:03
It's really clever however how Lurie and others embed the symmetric group action directly into the composition law of a colored operad.
04:17
@Tyler: out of curiosity, are you still collaborating with Lipshitz and Sarkar?
04:35
@MikeMiller yep
04:48
cool to see more homotopy in the low-dimensional/symplectic waters :) and a good excuse to learn some...
thanks. it's been a lot of fun to work for applications in other subjects instead of thieving from them
 
7 hours later…
11:24
I've been looking at Evens' thesis, here: dspace.mit.edu/bitstream/handle/1721.1/80453/… There is an intriguing paragraph on page 55. One thing that it says is that "Adams operations provide a way of picking out the actual vector bundles from the virtual vector bundles in K-theory. " How does that work?
12:08
@JonBeardsley I think that idea really goes back to the "category of operators" of May and Thomason. Lurie's definition of infinity-operad is an infinity-categorical version of that.
 
3 hours later…
14:41
Do we have an analog of J homomorphism for higher K theory or something related to them? When thinking about K(1) case I realize that J is something way more powerful than the Hurewicz map in detecting elements, so if we have such a thing our life might be way easier.
15:02
@MingcongZeng You may want to check this out: arxiv.org/abs/1210.2472
Hmm, the title is really precise
15:39
@RuneHaugseng oh neat. i didn't know this had a name!
16:01
Just had to use this monstrosity $End((sSet_{/BGL_1(R)})^\circ)^{op}$
yeah, it's really fantastic that we have both "operator categories" and "categories of operators"
17:05
And operads over operator categories also have categories of operators...
17:52
@JonBeardsley whats the \circ mean?
18:41
@crystalline subcategory of bifibrant objects
that's supposed to be the endomorphism operad of that monoidal category, augh
18:52
Actually, as written that doesn't make sense.
The op should be inside.
19:09
ah, i usually see ^{cf} for that, but \circ seems good
Oh, sorry, yeah, just trying to stay in line with Lurie's notation.
cf is probably more perspicuous, although it could possibly be confused with "cofibrant"
19:22
actually now that i think of it, ive even seen Int(-) in some older papers ("interior" i guess) so this seems in line with that
19:44
Right. Since \circ sometimes mean interior as well.
 
2 hours later…
21:51
Lurie says in 4.1.3.6 that if you take the subcategory of cofibrant objects of a monoidal model category that it "inherits" a monoidal structure. Is the tensor product of cofibrant objects usually cofibrant again?
That's part of the definition of a monoidal model category
The tensor product is a left Quillen bifunctor
Aha.
But this is not the case for fibrant objects, so why does he not make any restrictions when talking about $A^\circ$?
I guess he doesn't need that actually, in, e.g. Variant 4.1.3.17...
...The mapping spaces are just in A.
Hmmm.
That's why he has to define a simplicial operad rather than a simplicial monoidal category
Right okay... hrm...
22:07
@RuneHaugseng do you know what goes wrong with identifying, say, Ass objects in this simplicial operad by actually looking at maps from, like, the Ass colored operad into it?
22:22
Ass isn't a cofibrant simplicial operad
Hmmmm, so there are problems like, applying the nerve construction or something?
Well, a map from Ass will give you a map of infinity-operads, but you don't necessarily get all of them unless you take a cofibrant replacement of Ass
Ah, right so this was my other question, suppose I want to go {algebras in C}-->{algebras in N(C)}, Lurie seems to only say there's a problem going the other way?
Well, I guess there isn't quite a Quillen equivalence known yet between infinity-operads and simplicial operads, so technically that's not proved yet
Sure, there is a map like that. Is that what you're asking?
Yeah, I mean, it seems obvious, take an algebra in C, look at the endomorphism operad, End(C), you should have a map Ass-->End(C), giving an algebra the underyling monoidal quasicategory of C
(after applying operadic Nerve)
22:28
An algebra gives a map between simplicial categories of operators, and you're just taking the nerves of those
right. agreed. okay.
nice.

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