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Stream: community: general

Topic: Community

Aleks Kissinger (Apr 28 2020 at 09:57):

@Arthur Parzygnat Here are instructions for joining a couple of the main CT mailing lists:

• Categories: https://www.mta.ca/~cat-dist/
• Applied category theory: http://www.appliedcategorytheory.org/links/

Arthur Parzygnat (Apr 28 2020 at 10:08):

Aleks Kissinger said:

Arthur Parzygnat Here are instructions for joining a couple of the main CT mailing lists:

• Categories: https://www.mta.ca/~cat-dist/
• Applied category theory: http://www.appliedcategorytheory.org/links/

Thanks!

Aleks Kissinger (Apr 28 2020 at 10:17):

If you are interested in quantum stuff, there is also:

• Quantum-foundations: http://www.cs.ox.ac.uk/activities/quantum/ (scroll down to "Mailing Lists")

Benoit Valiron (Apr 28 2020 at 12:03):

It seems that the link that is given on @John Baez's website for joining this community is outdated (as of today). Is it possible to get a new one? The ZX-calculus crowd is eager to join!

Jules Hedges (Apr 28 2020 at 13:49):

If you click on the gear menu and go "invite users" there's a button to generate a fresh invite like (which work for 10 days)

Henry Story (Apr 28 2020 at 14:51):

Just a simple question. In the Category of Boolean Algebras CABA where $\overline{A}$ and $\overline{B}$ are boolean algebras, are the atoms of $\overline{A+B}$ the elements in $Set$ of $A \times B$ or $A + B$? So if in Set A = {$a_1, a_2, a_3$} and B = {$b_1, b_2, b_3$} then in CABA $\overline{A}$ will have the same elements as A as atoms and similarly for B. But what are the atoms of $\overline{A+B}$ in CABA? Will it be {$\overleftarrow{a_1}, \overleftarrow{a_2}, \overleftarrow{a_3}, \overrightarrow{b_1} \overrightarrow{b_2}, \overrightarrow{b_3}$} (where I use the arrows to indicate right or left injection). But $\overline{A+B}$ in CABA corresponds to $A \times B$ in Set, so it would also make sense for these to be pairs ($a_x,b_y$}...
Mhh. I got an answer on Math StackExchange which seems to indicate that $\overline{A+B}$ has as atoms the elements of $A \times B$ in Set meaning that coproduces of boolean algebras are bigger than products... (if so the mind boggles)

Nathanael Arkor (Apr 28 2020 at 14:58):

@Jules Hedges: I believe only moderators are able to generate invite links.

Jules Hedges (Apr 28 2020 at 15:02):

Ah sorry, here you go: https://categorytheory.zulipchat.com/join/r7drumha4lzkmvn005iw5rq8/

Dan Doel (Apr 28 2020 at 15:03):

@Henry Story The atoms are singleton sets of pairs, and the inclusions don't preserve atoms, I believe. For instance you have $\overleftarrow{a_1} ∧ \overrightarrow{b_1}$ in $\overline{A+B}$.

Dan Doel (Apr 28 2020 at 15:05):

$\overleftarrow{a_1} = a_1 × B$, I think.

Henry Story (Apr 28 2020 at 15:09):

The thing is that $\overline{A \times B}$ will then have to be injections of either A or B...

Reid Barton (Apr 28 2020 at 15:10):

I think your notation is not consistent, and possibly confusing you. Also, this seems like the wrong place for this discussion.

Henry Story (Apr 28 2020 at 15:12):

Reid Barton said:

I think your notation is not consistent, and possibly confusing you. Also, this seems like the wrong place for this discussion.

I was trying to find a notation to help distinguish between objects in Set and those in CABA. I am open to better conventions. Those are just the first I could think of right now.
Where do you think is a better place for this discussion?

Reid Barton (Apr 28 2020 at 15:14):

Maybe #learning: basic questions ?

Henry Story (Apr 28 2020 at 15:15):

ok, good Idea. I'll repost there. Can someone suggest a better notation to differentiate objects in Set and CABA. Perhaps just superscripting with $A^{op}$?

Dan Doel (Apr 28 2020 at 15:25):

I think the mentioned confusion is whether you mean $\overline{A + B}$ to be the CABA corresponding to $A+B$ or the coproduct of two CABAs. It seemed like the latter, but looks like the former.

Benoit Valiron (Apr 28 2020 at 15:52):

@Jules Hedges Thank you!

John Baez (Apr 28 2020 at 18:59):

Benoit Valiron said:

It seems that the link that is given on John Baez's website for joining this community is outdated (as of today). Is it possible to get a new one? The ZX-calculus crowd is eager to join!

Here is a new link:

https://categorytheory.zulipchat.com/join/u4h1nwjtpcr0blvjpg4kzanm/

I updated it on my webpage for the Category Theory Community Server. It'll last 2 weeks, or maybe 10 days.

সায়ন্তন রায় (Sep 12 2020 at 06:42):

I think that there are too many inactive topics under the stream learning : questions. Wouldn't it be a good idea to merge them?

Jules Hedges (Sep 12 2020 at 10:21):

I disagree, we're trying (and probably failing miserably) to be less intimidating to newcomers, and over-admining the questions channel could quickly degenerate into MathOverflow levels of unfriendly

Reid Barton (Sep 12 2020 at 10:32):

Topics are like the subject lines of emails--you wouldn't go back and merge the subjects of different conversations that have concluded.

Notification Bot (Sep 14 2020 at 21:08):

This topic was moved by Matteo Capucci to #philosophy > univalence irl