The h Bar

if set $A$ is larger than set $B$ and $C$ is the set $A \times B$ do the ordered pairs where B no longer has a member at $a$ just return $\langle a,null \rangle$?

0celo7

Holy shit

@BernardMeurer this is insane

barrycarter

@Obliv Umm, no.

Best out of context quote

Obliv

isn't the cartesian product the ordering of all members of $A$ and $B$

barrycarter

@Obliv A x B doesn't require A and B to be the same size.

0celo7

5:40 PM

@BernardMeurer I don't have the money

Bernard Meurer

@0celo7 You cast this onto yourself

Obliv

what would it return at the elements of $A$ where there is no corresponding elements of $B$? just a 0?

0celo7

@BernardMeurer will you take a book?

Bernard Meurer

@0celo7 I'll take beer & barbecue

Or Shankar :D

barrycarter

@Obliv What do you think A x B is if A = {1,2} and B = {X,Y,Z}?

0celo7

5:42 PM

I need Shankar for my work @BernardMeurer

Bernard Meurer

@0celo7 Well that's the only book you have I'm interested in

You'll be paying me with some ribs

barrycarter

Hopefully pork or beef?

Obliv

I thought maybe $\{ \langle 1,X \rangle , \langle 2,Y \rangle , \langle null,Z \rangle \}$

Bernard Meurer

@barrycarter Human

barrycarter

@Obliv Umm, no. It's { {1,X}, {1,Y}, {1,Z}, {2,X}, {2,Y}, {2,Z} }

Obliv

5:44 PM

oh i'm stupid. thanks @barrycarter

barrycarter

@Obliv its not per element multiplication, it's set multiplication

Obliv

ok

barrycarter

@BernardMeurer You know, Adam got a girl for a single rib. Settling a $20 debt for a rib seems pricey.

Bernard Meurer

@barrycarter haha

barrycarter

Although, I suppose there are places, like TN, where you can get a girl for $20

For an hour anyway.

0celo7

5:45 PM

@barrycarter She's usually in the $30 range

barrycarter

Even on Toothless Bertha's House of Whores Wednesday Discount Night?

Oh, wait, I use the coupon, never mind.

Bernard Meurer

@0celo7 Who?

barrycarter

Toothless Bertha... the safe alternative for BJs.

0celo7

@BernardMeurer Rebecca

barrycarter

Backdoor Becky?

0celo7

5:48 PM

@barrycarter you'll get a kick out of this one

My gf is from AL

barrycarter

Did she have a banjo on her knee?

Bernard Meurer

@0celo7 one of the babies picked food on his own !

0celo7

@barrycarter she can play the banjo with her tongue

barrycarter

I'm sensing an ornithological theme here.

You're a lucky man.

0celo7

Who said I'm a man?

barrycarter

5:49 PM

Kin she also cook up a mess o grits real fine?

Boy

0celo7

I'm genderfluid

barrycarter

So you're a gender gas or a gender liquid?

Obliv

1) A binary relation on a nonempty set $A$ is a subset $R$ of $A \times A$ and we write $a~b$ if $(a,b) \in R$. Doesn't this make sense if it said a set $R$ instead of subset?

0celo7

@barrycarter Nonnewtonian gender

@barrycarter never asked, don't like grits

barrycarter

@Obliv Yes, it would still make sense.

A x A is a set, R is a subset of A x A

Obliv

5:51 PM

I'm confused with this statement in general. $\{a,b\} \times \{a,b\}$ is just $\{\langle a,a \rangle, \langle a,b \rangle , \langle b,a \rangle, \langle b,b \rangle \}$. so like where is the relation even present?

Bernard Meurer

@0celo7 I'm a non-hausdorff

0celo7

@BernardMeurer are you really coming to Memphis this summer

Bernard Meurer

@0celo7 I might, dunno yet, gotta check on the $$

barrycarter

@Obliv No, they're saying that a binary relation is some subset of A x A

0celo7

Or is it Nashville?

barrycarter

5:52 PM

Like the relation "<" on {1,2,3} would be { {1,2}, {1,3}, {2,3}}

0celo7

I can't remember Michelle's plans

Obliv

oh..

Bernard Meurer

@0celo7 The barbecue's in memphis

barrycarter

@Obliv I'd invite you to go private and do some "real" math, but I'm afraid I've only allocated half a day to waste on chat today, and that ends in 6 minutes.

Obliv

@barrycarter I'm just learning definitions/preliminaries of this book still LOL. But, I've learned a lot so far and I'm thankful for your help thus far.

yeah I get that $R$ is just a subset of the total cartesian product of the set on itself.

barrycarter

5:54 PM

@Obliv Sure thing. It sometimes seems like you're jumping around randomly in the book. Is this the case?

Correct, a relation is a subset of A x B. In this case B=A

Obliv

no. I think of things sometimes not mentioned in the book otherwise I'm going chronologically.

just curious, how come you never use latex commands @barrycarter

Bernard Meurer

@0celo7 Shit, flights to knoxville are SO cheap

barrycarter

@Obliv I'm allergic to latex

Obliv

what a rare condition..

barrycarter

Yes :P

Bernard Meurer

5:55 PM

@0celo7 400USD the two way

barrycarter

I don't know TeX that well.

And I think it sometimes obfuscates instead of elucidates.

0celo7

@barrycarter literally never true.

Obliv

just look up commands as you go and you'll learn quickly. I think it makes things cleaner.

barrycarter

What, Ocelot?

Obliv

instead of x^2 + 2 you have $x^2 + 2$ :D

barrycarter

5:57 PM

@Obliv I'm a TeX hold out

Plus my stupid browser won't render TeX unless I visit the bookmark each time.

Superscripts are for wimps.

Bernard Meurer

@barrycarter $\LaTeX$ is always better

barrycarter

It looks nicer, maybe.

0celo7

How could it make things more confusing

Obliv

i used the link on the top right of this page to get a bookmark that renders any tex on the page. you only have to click it once unless you close the page

0celo7

Ever

barrycarter

5:58 PM

Besides, he asked me about latex, not LaTeX :P

0celo7

The answer is that it doesn't

barrycarter

@Obliv That's how it's supposed to work, but it's broken somehow for me. It used to work fine.

Obliv

It works for me on chrome & nightly

barrycarter

Well good for you :P

Obliv

i'm guessing it would work on firefox too

barrycarter

5:59 PM

Yes, it used to. I probably just need to look into it, but I don't care.

0celo7

You have to click chatjax every time you refresh

Did you bookmark it?

barrycarter

In my case, I have click chatjax even when I don't refresh.

Yes, its bookmarked.

It's a browser issue on my side.

0celo7

What browser?

barrycarter

Firefox old version

0celo7

My god

Use Chrome new version

Obliv

6:01 PM

shouldn't the statement I said above actually be a relation instead of a binary relation?

a binary relation is between 2 elements. So it would be a set of 1 ordered pair? o_o

ACuriousMind

I think you should take a step back and go about this a bit slower. I don't think you've gotten a single definition right from what you've posted thus far.

Obliv

my book said that was what a binary relation was.. it lied

Bernard Meurer

@ACuriousMind Do you want to watch bald eagles with me?

ACuriousMind

Read the definition. Then read the examples (if the book gives no examples, switch to one that does). Think about why every example is actually an instance of the definition.

@BernardMeurer Is that a euphemism?

Bernard Meurer

@ACuriousMind ustream.tv/channel/Ws8PbVWq5Xs

Nope

Obliv

6:05 PM

nevermind it defined it correctly. I have no idea why I thought it was something else.

is there even a formal definition for just "relation" between objects?

ACuriousMind

6

Q: Is watching porn in university a crime?

I am about to start my graduate studies in an American university, moving from my native Peru. Over the course of my under-graduation, I have developed this strange habit of watching porn at odd times, say afternoon, or morning. Sometimes I watch in classroom too, of course, reducing the volume t...

the fuck is this?

Obliv

LOL

that's so fucked. porn is just such a stupid thing and for him to think it's okay in academia is just despicable.

barrycarter

@Obliv I got a reprieve. I can help you w/ math in a private room away from all these "physicists" provided you don't make fun of my little latex problem.

But it's not a crime.

Obliv

well unless my questions aren't wanted I feel like asking to an audience is better than having a single source. no hard feelings @barrycarter I like mathematicians and physicists equally :p

ACuriousMind

@barrycarter If you read the question, it's more about whether it is considered acceptable, the title is a slight misnomer

barrycarter

6:12 PM

@Obliv Fair enough, I'm getting a little distracted, but I can keep trying to help

ACuriousMind

I'm baffled that this needs to be asked, though.

Obliv

thanks.

barrycarter

@Obliv As you learn more, you will understand why mathematicians are better :P

ACuriousMind

Then again, I'm regularly baffled by what passed for a good question at academia.SE, so that doesn't say much... :P

Obliv

the internet allows for people to ask idiotic questions without feeling bad. If he asked that to a public audience in real life, i'm sure he would feel a lot different. @ACuriousMind

barrycarter

6:13 PM

Sounds more like an April Fool's Day prank

I, personally, would cheer him on.

Obliv

why...

barrycarter

Porn is awesome

Obliv

i'm so tempted to star that.

barrycarter

Go for it :)

It can provide a good break from studying.

Obliv

but why IN the class?

barrycarter

6:16 PM

Hmmm, OK, that one's a bit weird.

Obliv

just a bit.

barrycarter

I mean, if the class itself isn't getting you excited, you're taking the wrong class.

Real mathematicians don't need porn (to do mathematics)

ACuriousMind

@barrycarter Relevant SMBC

Obliv

many people don't realize what porn-addictions can do to people. People just do stupid things when they aren't in control of themselves when those instincts kick in.

barrycarter

@ACuriousMind Ouch! I'd say the exact opposite.

@Obliv I am not aligned to your political views.

I do think porn is awesome, but agree that in class is not a good time to view it.

Obliv

6:45 PM

A partition of A is any collection $\{ A_i | i \in I\}$ of non empty subsets of A (I some indexing set) such that a) $A = \cup_{i \in I} A_i$, and b) $A_i \cap A_j = \emptyset $ for all $i,j \in I$ with $i \ne j$ (i.e, $A$ is the disjoint union of the sets in the partition).

I have a question about the definition of this partition

What does $\cup A_i$ mean? Does it mean the union of all the partitions of A?

Tuntuni

Yes

Obliv

Also, does $A_i \cap A_j = \emptyset$ mean they never intersect?

Tuntuni

That's right. No elements in common.

Obliv

thanks

Tuntuni

No problem. :-)

Obliv

6:56 PM

if ~ defines an equivalence relation on $A$ then the set of equivalence classes of ~ form a partition of $A$. Is this essentially saying the binary [equivalence] relation on $A$ is a subset of $A$?

a partition of $A$ is a subset of $A$, right?

yuggib

7:13 PM

no, a partition of a is a set of subsets of $A$

is a subset of $2^A$

the set of parts of $A$

barrycarter

7:31 PM

It's a way of breaking A into disjoint subsets that make up all of A

Obliv

7:55 PM

when it says the set of equivalence classes of ~ , is that equivalent to saying the binary relation on A using the ~ relation?

also @ACuriousMind is it true that carbonated water is the default water in Germany?

user507974

@Obliv is that what mineral water is

Obliv

don't ask me..

probably?

ACuriousMind

@Obliv If you mean that you'll get carbonated water when simply ordering "water" then yes, although many servers will ask what exactly you want.

barrycarter

@Obliv Sort of, yes.

ACuriousMind

@Obliv That sentence doesn't really make sense to me, but if you're asking whether the set of equivalence classes is the same as the relation as a subset of $A\times A$, then no.

Obliv

7:59 PM

any other countries where they do that? My friend says that he always half-expects drinking carbonated water when he takes a sip of water now. Traumatizing experience smh

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