The h Bar

0celo7

12:00 AM

Not why block me, but why take me off?

Danu

0celo7 loves being insulted :P

0celo7

@Danu No, I want to understand

DanielSank

@0celo7 Because you were posting a lot and almost all of it was either pithy retorts or requests for help on topics I know nothing about.

0celo7

@DanielSank I apologize

I admit, I was trying to outsmart you

DanielSank

@0celo7 Why? You weren't doing anything objectively wrong.

0celo7

12:00 AM

Eh, I was

I remember asking you about module tensor products

DanielSank

If you want to come here and beg for homework help that's not my problem: I just click "ignore".

peterh

I think it is the limit of this communication form. I've always thought on a chatroom, where the communication wouldn't be linear, but DAG-like

ACuriousMind

@DanielSank I have used it for the past months, and while it improves my experience, I'm not satisfied. Although, perhaps I should try the "nuclear option" you suggest and make it clear that I'll also ignore people who engage those I ignore.

DanielSank

@0celo7 Yes, that was annoying, so I clicked ignore.

0celo7

...homework?

Seriously?

DanielSank

12:01 AM

@peterh You know, a coworker mentioned that idea....

@0celo7 whatever

peterh

the main reason, why such type of chat isn't common until now, that it would require high-quality graph visualisation and the SE isn't strong in complex algorithms

0celo7

I'm confused

DanielSank

But yes, you were begging for homework help rather often.

It was very annoying.

0celo7

o.o when have I begged for homework help

Danu

^all the time

DanielSank

12:02 AM

@0celo7 I don't care to search the chat logs.

^^ that

0celo7

@Danu No, not possible.

ACuriousMind

@0celo7 Be mindful that he can't actually tell which of your problems are homework or not.

Physics Guy

Watching the discussion while hearing rock music.....yeah that's good.

Danu

I'm disengaging

DanielSank

@0celo7 See this is the annoying stuff.

2

Goodbye.

0celo7

12:02 AM

I've asked @ACuriousMind maybe three times for homework

Danu

^^

DanielSank

See how easy that was?

No argument. No insults.

0celo7

...oh my god

what just happened

Danu

@DanielSank Alright I'll give it another shot.

peterh

@DanielSank The DAG-like chat?

Danu

12:03 AM

But it didn't really help last time I tried :P

DanielSank

@peterh Yes.

0celo7

I...I don't beg for homework help

DanielSank

@Danu Helped me a lot. I was getting really annoyed by one user. Activate ignore feature. Done.

0celo7

@ACuriousMind Can you please explain...

Danu

It's not good that you can still see that people on "ignore" are in the room, and in fact when exactly they're posting a message.

DanielSank

12:04 AM

If I show up and there's a string of someone talking to themself, then I know who's on the other end (at least to some approximation) and I can choose whether or not to join in.

If that user is peppering a conversation I care about with other stuff, I just don't see it.

0celo7

I must be severely autistic, because I do not see what just happened, I simply do not understand

DanielSank

It's great.

ACuriousMind

@0celo7 You beg for help with whatever problem you're currently having. I don't think that the part that annoys Daniel about your behaviour is that he thinks it's specially homework you're seeking help with.

Danu

@DanielSank Iunno

0celo7

I don't beg

Physics Guy

12:05 AM

@Ocelo7 They wanted to provoke you.

0celo7

I begged for the flow thing because I was desperate

The vast majority of times, I ask you once

Danu

In any case @DanielSank, the biggest problem is honestly that I've lost my main teachers on math.se due to chat annoyances

Obviously, I cannot force them to make optimal use of the "ignore* feature

However, it would be very valuable for me to have continued "access to their knowledge"

0celo7

@ACuriousMind how am I begging?

Danu

Hence, me using the ignore feature doesn't solve my most essential problem

0celo7

I don't see the difference between begging and simply asking...

ACuriousMind

12:07 AM

@Danu That you're an egoist? ;P

bolbteppa

Sounds like a lot of self-imposed problems tbh, relaxing and meditation helps

Danu

@bolbteppa What?

Physics Guy

Ok, guys, I leave. See you.

Danu

How is the fact that the two users I value most in math chat left a "self-imposed problem"?

ACuriousMind

@0celo7 ...and if I don't respond or don't know, you start to ping everyone else entering the room if they know about it.

0celo7

12:08 AM

@ACuriousMind Only in very select cases

peterh

@DanielSank Many forums, use already a tree-like messaging system. All of them looks hilarious, but it shouldn't be so

Danu

@ACuriousMind That's a feature!

Physics Meta

0

Q: guest chat session top guest wishlist/ call for desired speakers

the new Physics SE guest chat sessions have gone generally well this summer (some brief summary/ history); we now have 3 basically successful events with talented/ qualified speakers and am personally pleased/ happy with the outcome so far which for me is mostly "better than expected" overall. it...

0celo7

And 99% of the time, it's just Danu.

DanielSank

@Danu That really sucks.

0celo7

12:09 AM

I honestly thought I was asking less questions

Danu

@DanielSank It indeed does.

DanielSank

@bolbteppa That makes no sense.

Danu

The result is that I've bailed on that chat room now.

DanielSank

Relaxing and meditation doesn't bring Shifrin back to chat.

bolbteppa

@Danu you can't control the way a bunch of people freely choose to chat, saying "Just like I don't like the way this chatroom is headed currently" and offering authoritarian solutions is a big self-imposed problem that can be solved by chilling out

DanielSank

12:10 AM

@Danu So it's a chain reaction.

Danu

@bolbteppa OK dude, whatever you say

bolbteppa

Same with people getting frustrated by a silly chatroom, I mean there are better things in life

Danu

@DanielSank Clearly

ACuriousMind

@Danu If you say so ;)

DanielSank

@bolbteppa Dude... this chat room has solved research problems for me.

It's not silly.

ACuriousMind

12:11 AM

::takes off party hat:: It's not?

bolbteppa

haha

DanielSank

@ACuriousMind -_-

::chases @ACuriousMind out the door with a pointed stick::

::asks @ACuriousMind to come back::

0celo7

@ACuriousMind Was the chat better when I was banned?

ACuriousMind

@0celo7 You're not the problem everyone is talking about currently, don't flatter yourself ;)

@DanielSank ::crawls back::

0celo7

@ACuriousMind I didn't think so, but I'm certainly contributing.

And if people find me annoying, I can leave.

2

Danu

12:15 AM

@DanielSank You see, the above already makes the ignore feature pretty crappy

DanielSank

@Danu why?

Move on with your life.

so there's some sub-conversation going on. Who cares?

Danu

Haha

It's not that

DanielSank

ignoring isn't perfect but it's better than nothing.

Danu

It's just that, if I'm going to hang out in the chat then this is boring

DanielSank

@Danu -_-

Wanna talk about Chinese food?

Women?

Danu

12:16 AM

@DanielSank I'd love to

Integrals?

lol

Not about women

We can give each other integrals. That's fun, right?

ACuriousMind

wonderful collection of topics

DanielSank

12:16 AM

@ACuriousMind I thought so.

Danu

too many fucking problems going on with that shit

@DanielSank nope.jpg

DanielSank

@Danu Uh oh.

So you do want to talk about it :)

Danu

Nah

DanielSank

k

WillO

@ACuriousMind: I've been away, just returned and quickly read the scroll. Here's an idea, to which I've given no more than a second's thought, so it might be terrible, but:

DanielSank

12:17 AM

btw, our very own @BernardMeurer is the new Don Juan of Rio.

Danu

Chinese food is good though

DanielSank

Ask him about it.

WillO

You say that "ignore" doesn't work so well because you still see the others who are not ignoring those you ignore....

bolbteppa

How about translating homological algebra into the children's language of obstructions

Bernard Meurer

@DanielSank Shush

DanielSank

12:17 AM

@BernardMeurer Oh come on

Danu

I've recently been working a bit on Indonesian food

DanielSank

You deserve a bit of congradulations.

WillO

What about this: Without actually moderating the room, post, publicly, a list of people you think it's better to ignore --- and encourage others to ignore them also.

Danu

It's real easy---just put ketjap in everything hahaha

Bernard Meurer

Oh my god

lol

Danu

12:18 AM

@WillO lmao

bolbteppa

Where "Mayer Vietoris says that to work out the obstructions in AuB, that's like taking disjoint copies of A and B and looking at their defects, and then counting the ones you counted twice from their intersection that you ignored: it is the inclusion exclusion principle. The snake lemma tells you that if you were looking at n-dim holes, then you next need to take into account the n-1 dim holes - or the boundaries of the n-dim holes. "

Danu

Social experimentation mode: Engaged.

bolbteppa

I mean I don't think they know this insane subject has a children's explanation

Danu

That'd be super awkward

DanielSank

@WillO oh jeez

bolbteppa

12:18 AM

I just don't know it

DanielSank

Yeah, @Danu, put that in your profile.

LOLOLOLOL

WillO

@DanielSank: As I said, I gave this no thought before posting it....

ACuriousMind

@WillO That's either a really good bad idea or a really bad good idea ;)

peterh

@DanielSank Could quantum algorithms solve the bin packing problem in polinomial time?

Danu

@DanielSank I RECOMMEND YOU IGNORE THE FOLLOWING USERS:

DanielSank

12:19 AM

@peterh I have absolutely no idea.

bolbteppa

Sounds like a burn-the-witch level idea to me

Danu

[hyperlink that redirects to the current reader's profile]

Bernard Meurer

@WillO That's a formula for disaster

You'd be on my list lol

ACuriousMind

@DanielSank Well, I already know he's apparently got a girl in Wiesbaden now, what else is there to know?

@Danu lol

DanielSank

@ACuriousMind >.>

<.<

:]

Danu

12:21 AM

>.<

<.> (??)

ACuriousMind

Did you all eat something wrong or why are you making weird faces? :P

Danu

It's the strong whisky

WillO

Continuing with this possibly terrible idea: There could be a "recommended ignore" list that is maintained by a couple of elected moderators, who have no power to actually ban anyone.

Danu

^hahahahahaha

DanielSank

@ACuriousMind Just trying to bring little Bernie the accolades he deserves.

Danu

12:21 AM

sorrry for the rudeness

but that is just hilarious

DanielSank

It is hilarious.

ACuriousMind

@WillO "Ignore list curators"?

Danu

So @BernardMeurer tell me why you're the Don Juan

I volunteer to be the ignore list dictator

WillO

@ACuriousMind: something like that.

I'm doing my best to address your problem!

Danu

Hey @ACuriousMind

Bernard Meurer

12:23 AM

@Danu He's making it up

All I did was go out with a girl

Danu

You know what transversality is for submanifolds of $\Bbb R^n$?

I guess you do because surely 0celo7 asked you about it before

ACuriousMind

@WillO Well, I must say I'm not categorically dismissing your idea. I'm trying to evaluate how much trouble that would actually create, and how much it would save

Danu

@BernardMeurer I do that, too!

ACuriousMind

@Danu I don't know shit about transversality

Danu

Do you like her? :)

@ACuriousMind Okay, wanna hear a definition?

Bernard Meurer

12:24 AM

@Danu She's p cool, but she was here just for the olympics, she's from Wiesbaden

bolbteppa

@Danu you know the way in elementary calculus you can generate a curve through the intersection of two surfaces, e.g. the intersection of two planes is a line, that is transverality

Danu

Damn

And she left already?

ACuriousMind

@Danu Maybe?

0celo7

@ACuriousMind Oh, but only if you know an annoying asshole who did know lots about it

Danu

I could go by her place to declare your true, undying love @BernardMeurer

WillO

12:25 AM

@ACuriousMind: I quite agree with you that it could be either a very good idea or a very bad one.

DanielSank

@Danu He doesn't need your help.

Bernard Meurer

@Danu lol

Gonna have a gang of German physicists watching over her

DanielSank

@BernardMeurer show us a pic of your new SO?

Danu

@DanielSank Back off, mama bear ;)

ACuriousMind

@Danu I'll play the cheesy music, you'll sing, alright?

Bernard Meurer

12:26 AM

@DanielSank SO?

Danu

@ACuriousMind MY HEART WILL OOOON AND OOOOOOOON'

DanielSank

@Danu You have no idea... LOLOLOL

Bernard Meurer

@ACuriousMind Lol you'll play death metal, I know you

DanielSank

@BernardMeurer significant other

Danu

Celine Dion My Heart Will Go On

►

Bernard Meurer

12:26 AM

@Danu You really have no idea lol

Danu

Okay so definition time @ACuriousMind

Bernard Meurer

@DanielSank I ain't got no pictures

0celo7

@ACuriousMind Just tell him to ask me

I doubt you want to hear it from him since you didn't want to hear it from me.

ACuriousMind

@BernardMeurer Maybe, maybe not. Perhaps she's into death metal ;)

Bernard Meurer

@ACuriousMind She really isn't

She plays the Piano and likes Chopin

Danu

12:27 AM

Let $X,Y$ be smooth manifolds, and $f:X\to Y$ a smooth map; $f$ is transversal to a submanifold $Z\subset Y$ at the point $x\in X$ if $\operatorname{im}d_x f+T_{f(x)}Z=T_{f(x)}Y$.

ACuriousMind

My actions may also depend on the amount and quality of beer you provide me with

Danu

Pretty straightforward---think of it as a generalization of regular value to the case where $Z$ is not just a point but has nonzero tangent space

ACuriousMind

@0celo7 I have a feeling if he wanted to ask you he'd already have done it...

Bernard Meurer

@ACuriousMind Then I fear for my life

0celo7

@ACuriousMind Fine

ACuriousMind

12:29 AM

@Danu Alright (are the image and the tangent space allowed to have non-trivial overlap?)

Danu

Yes

Bernard Meurer

@ACuriousMind Idk if it interests you, but I just got the SACD mastering of almost all of Black Sabbath albums

Danu

So two orthogonal surfaces in $\Bbb R^3$ are transversal

0celo7

@ACuriousMind Yes, it's a vector space sum, not a direct sum.

Bernard Meurer

@Danu Also, SACD mastering of Rachmaninoff and Prokofiev's 3rd Piano concerto by Van Cliburn

Danu

12:30 AM

Now, if the map is an inclusion map $\iota:X\to Y$ then we say that $X$ is transversal to $Z$ if $\iota$ is

@BernardMeurer Sounds good

So now we have the notion of transversal submanifolds

ACuriousMind

@BernardMeurer Nice, although Black Sabbath aren't exactly my favourites

@Danu Okay, so what's the question?

Danu

One important point is that the transversality of $X$ with respect to $Z$ guarantees that the (local) defining functions of $X,Z$ are linearly independent, hence $\operatorname{codim}(X\cap Z)$ is the sum of the codimensions of $X$ and $Z$

Bernard Meurer

@ACuriousMind I like Black Sabbath for when I want to break shit up

WillO

So the map $f$ has just turned into an inclusion?

Danu

Hence, if $\operatorname{dim}X+\operatorname{dim}Z=\operatorname{dim}Y$ then their intersection is zero-dimensional

0celo7

12:33 AM

@WillO In the case when $f=\iota$ (inclusion map), yes, it's injective.

WillO

Oh, sorry. I'd overlooked the message with iota.

Danu

Now, finally my tiny question: The book states that in order to guarantee that this intersection is in fact finite, we need to assume that (1) both submanifolds are closed (topologically, I think) (2) one of the two is compact.

The latter is obvious to me, but the former is not. This should be very easy to see. Any quick answer?

WillO

Otherwise you could have infinitely many cross points, like the graph of sin(x) and the horizontal axis.

Danu

The question is why the condition (1) is necessary

I'm asking for a counterexample, basically

WillO

It's certainly not necessary.

0celo7

12:35 AM

Topologist's sine curve with an axis is a good counterexample.

Danu

@WillO Proof?

WillO

You need some condition, and that one will do, but you don't need that one.

0celo7

You need the intersection to be closed

Intersection of closed sets is closed

ACuriousMind

@Danu Take the whole manifold minus one point as one manifold, a point as the other. They're not both closed, but the intersection is finite?

WillO

For example: Take the area between y=x^2 and y=x^2+1.

Delete one point out of that somewhere in the middle.

Danu

12:37 AM

@ACuriousMind Haha yeah sure

0celo7

@ACuriousMind Like Willo said, it's not always necessary.

WillO

THat's not closed, but it still hits the axis in a finite number of points (namely one),, as it should.

0celo7

But there are pathological counterexamples if you don't do it, I think.

Danu

@ACuriousMind Let's exclude trivial cases where one of the two is 0-dim, compact.

Can you still give a counterexample?

0celo7

@Danu Graph of topologist's sine curve with a compact section of the $x$-axis including zero.

The sine curve is not closed (topologically).

Danu

12:40 AM

That's a better counterexample, thanks @0celo7

0celo7

@Danu You're welcome.

@Danu Do you see why compactness on one + closed gives finite intersection?

Danu

Yeah, that's no problem

Just not why it's necessary

(so it turns out it's not)

0celo7

@Danu Yeah. When you get to stability they'll probably say compactness is necessary, but really, it's just necessary to avoid pathologies.

They have a neat exercise where all of the stable classes fail in the noncompact case, I highly recommend doing it.

Danu

I already passed that part

I have to say that I think their presentation of the stability theorem is absolutely terrible

ACuriousMind

@Danu To see it's not necessary, a plane with one point removed (so it's not closed) and a line intersecting it would also have done it, no?

DanielSank

12:46 AM

Attention all:

I have just buried @BernardMeurer beneath the following insult: "If you hand an Argentine a bottle of rum and wait twenty minutes, he's speaking Portuguese."

Danu

In general, I feel that their proofs are lacking on the conceptual side of things

DanielSank

That is all.

Carry on.

Bernard Meurer

@DanielSank DOOD

Danu

@DanielSank The brag was too much, man :P

Bernard Meurer

I swear to god I'ma gonna beat your ass at smash bros

Danu

12:47 AM

Still you get a 5/10 for attempted epicness

ACuriousMind

@BernardMeurer hahahaha, that reaction is better than the joke...

DanielSank

@BernardMeurer Bring it.

@Danu Whatever. That's one of the best insults I've ever crafted.

ACuriousMind

But from what I've inferred, beating Daniel in Smash Bros is going to be hard

Might want to get him to drink that bottle of rum first to accomplish that

Danu

@DanielSank I love how you use "crafted" there.

Whitney Houston - I Will Always Love You - Lyrics

►

DanielSank

@Danu It's the influence of Russian, where insults are considered construction projects.

@Danu Excellent song. But why?

Danu

12:50 AM

Just felt right.

Bernard Meurer

@ACuriousMind Dude I will outdrink any non-german in this room

Danu

I'll take that bet.

Bernard Meurer

I have the liver of a 30 year old

Danu

I'm at 2 liters of beer and 3 whisky's

DanielSank

@Danu ?

How should I have delivered it?

Bernard Meurer

12:52 AM

3 doses of Whisky?

Danu

@BernardMeurer Normal-sized glasses

Bernard Meurer

That's a good mark

Danu

@DanielSank Not sure, but this was a bit over the top :)

Still, a good attempt.

Bernard Meurer

I'm currently at 5 L of beer and an unknown amount of stuff afterwards

But I got home :)

Danu

nonsense

DanielSank

12:53 AM

@Danu ::accepts criticism and will improve next time::

Trash talk is a skill.

Danu

@DanielSank I wish you good luck on your endeavours

DanielSank

@Danu Many thanks, good sir.

Danu

@DanielSank I think I will not attempt to beat my golden moment, ever

Bernard Meurer

::Appreciates a moment when I can read and understand all the messages::

DanielSank

Still, I feel that could take place as a "routine" insult to use against Brazilians.

It has the feel of an "old" cultural joke.

@Danu ....!?

Danu

12:55 AM

That's right

DanielSank

Black noise?

Bernard Meurer

@DanielSank I swear to god some brazilians will eat your kidney in front of you if you say that

Danu

@DanielSank Good, you remember.

DanielSank

@BernardMeurer YES! See, @Danu?!? It is good!

Danu

hehe

I guess it's lost on Europeans

Bernard Meurer

12:56 AM

@DanielSank Hmpf

ACuriousMind

@BernardMeurer With those people, does it actually matter what you say?

Looking at them funny probably also suffices

Bernard Meurer

@ACuriousMind Yes. Other parts you can't live without :)

ACuriousMind

Now I want a drink, but all I've left is gin and I'm out of tonic :/

DanielSank

I love my wife.

Danu

@ACuriousMind Water, close enough?

DanielSank

12:58 AM

Send her insult. Her response: That shall go on the books as a truly excellent insult".

Danu

(don't actually take that advice, plz)

ACuriousMind

@Danu lol

DanielSank

She appreciates me.

ACuriousMind

We did once resort in desparation to just mixing gin and rum. In a stein

Not recommended.

Danu

Heh

ACuriousMind

12:59 AM

Better than the rum with multi-vitamin juice, though

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