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Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
12:05 AM
no one does
 
user74918
user74918
D:
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
it is usually best to just ask your question
if you ask for experts on a subject, no one is going to volunteer without knowing what the question is
and then, it is very rare that questions require experts...
 
user74918
user74918
trying to find the number of graphs (which are connected) on a bipartite graph if all you know is A and B (the number of vertexes in each set)
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
up to isomorphism?
 
user74918
user74918
I am not famliar with what that means here
The question I posted is here math.stackexchange.com/questions/378609/…
 
Peter Tamaroff
Peter Tamaroff
12:09 AM
@MarianoSuárez-Alvarez Helloes, helloes.
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
if you think that there are 2^(ab) graphs, then no, you are not counting graphs up to isomoprhism :-)
hi, P
I expect your question to be very difficult, @user74918
maybe you can count the disconnected ones
using a recursion on a partition of connected components
that'l give you a recursive formula, at least
 
Peter Tamaroff
Peter Tamaroff
@MarianoSuárez-Alvarez How is it going?
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
not bad
 
user74918
user74918
@MarianoSuárez-Alvarez A recursive formula is what I am trying for
I tried to figure out how to count disconnected components but my answers are always off
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
the connected components of a bipartite graph are connected bipartite graphs
 
user74918
user74918
12:13 AM
yes
 
Peter Tamaroff
Peter Tamaroff
@MarianoSuárez-Alvarez That's good.
 
user74918
user74918
i asked another question to get the total number of "full" graphs (idk the term)
graphs that connect every vertex, connected or not
then from this i wanted to subtract the disconnected graphs
 
Peter Tamaroff
Peter Tamaroff
@MarianoSuárez-Alvarez There was a "Math Week" at the Pab II, apparently.
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
yes
every year there is one
 
Peter Tamaroff
Peter Tamaroff
@MarianoSuárez-Alvarez Oh. Didn't see any posters though.
 
user74918
user74918
12:24 AM
@MarianoSuárez-Alvarez If F(A,B) counts the number of full graphs (graphs that have at least one edge connecting to each vertex in both A and B), is there a way to leverage this to subtract out the disconnected graphs?
i don't know how to subtract out all possible sub partitions
i tried combinatorics but this double counted
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
leverage is a word that outside of business proposals always seems out of place
«i tried combinatorics but this double counted» Heh.
 
user74918
user74918
use, exploit, take advantage of
?
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
you double counted: combinatorics used correctly always givees the correct answer :-D
 
user74918
user74918
guns don't kill people etc
either way the answer's wrong XD
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
If I had time to do think about it, I would count the disconnected biparite graphs
 
user74918
user74918
12:26 AM
right, that is what i am trying to do
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
setting up a recursion involving the partition of connected components
 
user74918
user74918
but not sure how
yes
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
the connected components of a disconnected graph are smaller connected bipartite graphs
so sum over all possible partitions, &c
 
user74918
user74918
yes, but that is where i am stuck
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
how can you be stuck
that gives you the recursion
 
user74918
user74918
12:27 AM
i have clearly not set it up correctly
knowing what to do != being able to do it
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
well, think about it
I am in the middle of something right now :-)
 
Charlie
Charlie
1:07 AM
Hi @anon
 
anon
anon
yo
 
Charlie
Charlie
@anon how are you today?
 
anon
anon
meh
 
Charlie
Charlie
@anon oh!
 
anon
anon
are you keeping a log of my moods? :)
 
Charlie
Charlie
1:09 AM
@anon what happened?
 
anon
anon
eh, nothing
 
Charlie
Charlie
@anon oh
 
Jayesh Badwaik
Jayesh Badwaik
@WillJagy Wow, wow and wow!
 
Charlie
Charlie
@anon Goodnight, anon.
 
anon
anon
night
 
Victor
Victor
1:35 AM
Anybody could help me with a calculus question? math.stackexchange.com/questions/378851/…
 
Peter Tamaroff
Peter Tamaroff
@Victor You cannot find a primitive of that in terms of elementary functoins.
 
Victor
Victor
@PeterTamaroff - How to express it in terms of special function?
 
Gnintendo
Gnintendo
1:53 AM
Took my Linear Algebra final....
nailed it 8D
 
Jayesh Badwaik
Jayesh Badwaik
@Gnintendo Gr8!
 
anorton
anorton
It's always fun to nail a final.
 
Gnintendo
Gnintendo
yep
 
anorton
anorton
2:09 AM
Hey guys -- I finally changed my profile picture! :D
(It's not showing up here, though...)
 
Will Jagy
Will Jagy
@JayeshBadwaik, what are we Wowing about today?
 
Jayesh Badwaik
Jayesh Badwaik
@WillJagy Super Bayern.
:-)
 
Will Jagy
Will Jagy
7-0 over two legs. Amazing.
 
Jayesh Badwaik
Jayesh Badwaik
Yes.
They also played really good football, attacking one.
 
Will Jagy
Will Jagy
I thought Barca would pull back a little, although not enough. Never expected them to get crushed both home and away.
 
Jayesh Badwaik
Jayesh Badwaik
2:20 AM
Ahh. I was expecting them (Barca) to win 3-0 or something.
 
robjohn
robjohn
Is sports being discussed in the math chatroom?! Stop it!
3
People are going to get the wrong idea...
 
Will Jagy
Will Jagy
@robjohn, yes, that would be terrible. I asked Charlie to get in touch with Somaye, explain a little about Chat. Could work.
I also put some Shakespeare in this: math.stackexchange.com/questions/378331/…
 
robjohn
robjohn
I am getting upset at the impoliteness on the main site. The idea is to help those asking questions to improve them, not simply to bash people who ask questions that don't show "enough effort"
Supportive advice vs impoliteness
 
anorton
anorton
@robjohn I agree. I was going to start on a crusade to rid the site of low-work questions (and have ended up closing/downvoting quite a few), but have since decided that it's better to show kindness before using a mallet to coerce...
 
Will Jagy
Will Jagy
2:39 AM
Then I should say, fairly gently as I've posted this elsewhere, that I think the responsibility is on the person asking. Among moderators sticking around, I think Mariano is probably with you. I'm closer to Qiaochu, who is stepping down. I'm just observing, as I happen to be here when you mentioned this.
 
anorton
anorton
@WillJagy (To me, or to robjohn?)
 
Jayesh Badwaik
Jayesh Badwaik
@robjohn How do we handle the problem of very large number of questions and not enough "interested" answerers then?
 
Will Jagy
Will Jagy
To robjohn...
 
robjohn
robjohn
@JayeshBadwaik not by being impolite. We can do the same thing by being kind and helpful. It is asked in the FAQ to be kind.
3
I am not suggesting that we promote poor questions, but that we be kind and supportive about the suggestions.
 
anorton
anorton
Yeah. There's always a nice and a mean way to say something. Oftentimes, we (myself certainly included) can choose the mean way when we're fed up with a certain behavior.
We do want good questions, but we also want to leave a good impression on new users.
 
robjohn
robjohn
2:43 AM
@anorton I would suggest when you see a behavior that sends you over the edge, to take a step back and let someone else help them
2
@anorton that was not intended to be just to you :-)
 
Jayesh Badwaik
Jayesh Badwaik
@robjohn Ahh, yes, that is a reasonable stance.
 
awllower
awllower
3:24 AM
Really!
And they suspended users for having double accounts?
 
skullpatrol
skullpatrol
Yep...that's all I know.
 
awllower
awllower
I see.
Thank God I did not try to realize my previous idea of having multiple accounts!
:)
 
skullpatrol
skullpatrol
Maybe he got into a fight with a mod and admitted it himself.
 
awllower
awllower
Probably.
Oh, and thanks for answering!
 
skullpatrol
skullpatrol
np ;)
Etiquette

Civility is required at all times; rudeness will not be tolerated.

Be nice.
Treat others with the same respect you’d want them to treat you. We’re all here to learn together. Be tolerant of others who may not know everything you know. Bring your sense of humor.

Be honest.
Above all, be honest. If you see misinformation, vote it down. Add comments indicating what, specifically, is wrong. Provide better answers of your own. Best of all — edit and improve the existing questions and answers!
 
awllower
awllower
3:30 AM
:)
 
skullpatrol
skullpatrol
:)
 
Mariano Suárez-Alvarez
Mariano Suárez-Alvarez
4:02 AM
 
skullpatrol
skullpatrol
4:36 AM
This is what I got :D
 
math101
math101
5:06 AM
Hey guys
 
Gustavo Bandeira
Gustavo Bandeira
@math101 Yo!
 
math101
math101
Member me???
whtvr my scanner is misbehaving I think I am gonna head to bed before I turn into a pumpkin
 
Gustavo Bandeira
Gustavo Bandeira
@math101 ?
 
math101
math101
Do you remember me?
 
skullpatrol
skullpatrol
@math101 I do :D
 
Gustavo Bandeira
Gustavo Bandeira
5:33 AM
@math101 Nope. =/
 
skullpatrol
skullpatrol
@math101 Hello
 
Dominic Michaelis
Dominic Michaelis
6:02 AM
hi
 
skullpatrol
skullpatrol
huhu
 
Gustavo Bandeira
Gustavo Bandeira
6:22 AM
haha
@DominicMichaelis Hello!
 
Dominic Michaelis
Dominic Michaelis
@GustavoBandeira how are you ?
 
skullpatrol
skullpatrol
wtf >:-(
 
Gustavo Bandeira
Gustavo Bandeira
@DominicMichaelis I'm fine, you?
 
Dominic Michaelis
Dominic Michaelis
Bra Ket notation sucks so hard
 
Gustavo Bandeira
Gustavo Bandeira
@DominicMichaelis Why?
 
Dominic Michaelis
Dominic Michaelis
6:27 AM
waste of time looks awful isn't helpfull
 
Gustavo Bandeira
Gustavo Bandeira
What are you studying?
The reference I've found was about quantum states, is that it?
 
Dominic Michaelis
Dominic Michaelis
physics and math
 
Gustavo Bandeira
Gustavo Bandeira
What should be used in it's place?
 
Dominic Michaelis
Dominic Michaelis
normal math notation ...
 
Gustavo Bandeira
Gustavo Bandeira
I don't know what is normal math notation.
 
Dominic Michaelis
Dominic Michaelis
6:31 AM
well they use $\langle x |$ for $x^\ast $ for example and write $\langle x, A y \rangle$ as $\langle x| \hat{A}|y\rangle$
 
skullpatrol
skullpatrol
One could say that the only difference between math and physics is notation.
In some areas.
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol The first time I met the term: "Mathematical Physics", I was like: "What?! Wasn't it already mathematics?!"
 
Dominic Michaelis
Dominic Michaelis
nope at least the professor in physics ist just talking crap, he drops every necessary assumption
 
Gustavo Bandeira
Gustavo Bandeira
@DominicMichaelis Math professors talk only crap?
 
Dominic Michaelis
Dominic Michaelis
nope
 
skullpatrol
skullpatrol
6:35 AM
@GustavoBandeira Indeed Galileo said nature is written in the language of math.
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol Be careful with what these guys say.
Jan 28 at 20:29, by Gustavo Bandeira
As was his style, Kepler could not resist sharing his unique inter-
pretation of this mathematical observation. He assigned genders to the
solids and used duality to indicate sexual compatibility. The cube and
the dodecahedron (both dominant primaries) were male and contained the
female octahedron and icosahedron (secondaries). The tetrahedron was a
hermaphrodite because it contained itself. The faces and vertices were the
sexual characteristics because that was where the solids met.
Jan 28 at 20:29, by Gustavo Bandeira
> THE TETRAHEDRON WAS A HERMAPHRODITE!
 
skullpatrol
skullpatrol
Nice example :D
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin Are you a tetrahedron?
 
Lord_Farin
Lord_Farin
Eh. No?
 
skullpatrol
skullpatrol
(-:
 
Gustavo Bandeira
Gustavo Bandeira
6:45 AM
Guys, for serious.
Who's the world hottest female mathematician?
 
Dominic Michaelis
Dominic Michaelis
oh nice one now we have $\langle a, A a\rangle=\langle a,A a\rangle \cdot I$ where $I$ is the identity
 
Gustavo Bandeira
Gustavo Bandeira
(considering such a person can exist)
@skullpatrol No. I'm just in good mood.
 
skullpatrol
skullpatrol
No results found for "the world's hottest female mathematician".
:-)
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol They should be all hairy, isn't it?
Charlie is really beautiful.
I thought she was ugly like shit, but she's pretty.
 
Lord_Farin
Lord_Farin
:)
 
Gustavo Bandeira
Gustavo Bandeira
6:51 AM
@Lord_Farin ?
 
skullpatrol
skullpatrol
@GustavoBandeira Do you have a "sexy female mathematician fantasy"?
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin I really don't have better things to say and when I do, people don't reply.
It feels like talking alone.
 
Lord_Farin
Lord_Farin
@GustavoBandeira I'll conjure up a nice reply for you. It'll take a moment :)
 
robjohn
robjohn
@GustavoBandeira Does that mean when people reply, what you've said is of no value? :-)
 
Gustavo Bandeira
Gustavo Bandeira
@robjohn No. It means that when I talk something of value, people don't reply.
 
robjohn
robjohn
6:55 AM
@GustavoBandeira contrapositive...
 
Lord_Farin
Lord_Farin
@robjohn A clear misinterpretation. What @Gustavo means is that we can discern perfectly whether or not what he says is the best he can say; if not, we don't deem it worthy a reply :). (Ah, I love the conscious misinterpretation of sentences in the morning :).)
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin I guess I know what you are conjuring.
 
skullpatrol
skullpatrol
@GustavoBandeira Here ;-)
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol You don't have permission to access /i/funpic/A_Sexy_Mathematician-2474.jpg on this server.
 
Lord_Farin
Lord_Farin
@Gustavo Regarding my now "smilied" comment: I am always amazed at how tied up people are to the real world. MSE and this chat could be a place for minds to meet without the limitations of physical reality (and also without some of its benefits). Perhaps I'm overly centred on the intellectual side of things; in any case, your comment struck me by its discrepancy with this utopian sketch of mine.
 
Gustavo Bandeira
Gustavo Bandeira
7:05 AM
@Lord_Farin I understand the feeling. Sometimes I feel the same at some places I go, but people just stare at the weird things I say and the silence rules the place. When I'm here, most of the time you guys are talking about something in the intelectual side of things, I feel unable to understand/interact.
 
robjohn
robjohn
@GustavoBandeira :-(
 
Lord_Farin
Lord_Farin
@GustavoBandeira Why do you feel that way? (I'm genuinely interested in trying to resolve this.)
 
nerdy
nerdy
Is there any real difference between an n-tuple and a ordered set with n elements ?
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin Well. I don't know much about mathematics, my knowledge of interesting things is pretty limited, supose you're talking about Lemmas in Topos Theory (for example), Imagine you said: "C has a small set of generators, and admits all small colimits. Furthermore, colimits commute with fiber products." - When I read that I think: "What the hell is that?!"
And I won't bother people to give me lectures about what they're studying.
People have their lives and their schenduled time, etc.
 
Dominic Michaelis
Dominic Michaelis
never thought that it happens but actually i have aquestion about linear algebra
 
Lord_Farin
Lord_Farin
7:11 AM
@GustavoBandeira Usually the level of the math here is a bit more mundane, but I can see where you're coming from now.
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin Profile?
 
Lord_Farin
Lord_Farin
@Gustavo Have you ever tried / Are you interested in self-study?
Nvm :)
 
Gustavo Bandeira
Gustavo Bandeira
Yes. I'm doing that now.
 
nerdy
nerdy
Is there any real difference between an n-tuple and a ordered set with n elements ? I cant find that
on the internet
 
skullpatrol
skullpatrol
 
Gustavo Bandeira
Gustavo Bandeira
7:12 AM
But I've started almost from zero, as I told in my profile.
@robjohn Why the sadness?
 
Dominic Michaelis
Dominic Michaelis
How to show that when $V$ is a unitary vector space, $f,g$ are normal endomorphism with $f\circ g=g\circ f$, then there is a orthonormal basis of $V$ such that the elements of the basis are eigenvectors of $f$ and of $g$
 
Lord_Farin
Lord_Farin
@nerdy I'd say they're interdefinable. Presuming you mean a totally ordered set.
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol Well, even I can understand the content of the blackboard.
 
nerdy
nerdy
hmhm makes sense
 
Lord_Farin
Lord_Farin
@skullpatrol That's not math. That's arithmetic.
 
nerdy
nerdy
7:13 AM
lol
 
Gustavo Bandeira
Gustavo Bandeira
@skullpatrol It would be cool If the content of the blackboard was Mochizuki's work. =D
 
robjohn
robjohn
@GustavoBandeira I was sympathizing with the error in retrieving the image.
 
Gustavo Bandeira
Gustavo Bandeira
Which I can only dream of understand someday and by now, I can only venerate as a god.
 
skullpatrol
skullpatrol
@Lord_Farin Are you saying $$arithmetic \neq math$$?
 
Lord_Farin
Lord_Farin
@skullpatrol Yes.
 
Gustavo Bandeira
Gustavo Bandeira
7:15 AM
@skullpatrol It really is.
I guess it would be better to say: $arithmetic \in math$
 
Lord_Farin
Lord_Farin
@DominicMichaelis What is a normal endomorphism? Is a unitary VSp effectively an inner product space (i.e. a Hilbert space without completeness imposition)? (Or: I'll likely not be able to help you :).)
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin Sometimes, for knowing who's there, the only accessible thing I have to say is really bullshit.
 
Dominic Michaelis
Dominic Michaelis
@Lord_Farin a normal endomorphism is an endomorphism such that $f^\ast \circ f = f\circ f^\ast$, a unitary vectorspace is (isometric isomorph to) $\mathbb{C}^n$
 
Lord_Farin
Lord_Farin
@GustavoBandeira So what are you studying atm?
 
Dominic Michaelis
Dominic Michaelis
with the standard hermitian scalarproduct on $\mathbb{C}$
 
Lord_Farin
Lord_Farin
7:20 AM
@DominicMichaelis Ok, thanks.
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin I'm following the Oxford and Cambride syllabus on math. Now Complex Numbers and Sequences.
 
Dominic Michaelis
Dominic Michaelis
I think it is not trivial but it is an homework problem of a friend in linear algebra and I got no rigorous proof
and even the finite dimensional case is not obvious to me
you can show that the eigenspaces of $f$ are invariant under $g$
 
Gustavo Bandeira
Gustavo Bandeira
and groups, but nothing very deep.
 
Dominic Michaelis
Dominic Michaelis
so if the eigenspaces of $f$ are onedimensional it is obvious ;)
 
Lord_Farin
Lord_Farin
@DominicMichaelis Yes, I was just going to say that.
@DominicMichaelis Ok, so maybe WLOG reduce to the case of only one eigenvalue.
@GustavoBandeira If I look back at what I was able to do when I first entered university, you shouldn't be worrying. It'll come.
 
Dominic Michaelis
Dominic Michaelis
7:25 AM
yeah this reduction is no problem ($f$ one eigenvalue $g$ may have arbitrary)
 
Lord_Farin
Lord_Farin
@DominicMichaelis Ah. We have to use normality of course.
Do you know Jordan normal form for matrices?
 
Dominic Michaelis
Dominic Michaelis
yeah but does it hold for infinite dimensional case ?
 
Gustavo Bandeira
Gustavo Bandeira
@Lord_Farin Yeah, I do believe that. Some time ago I was reading a book on category theory - the conceptual mathematics book.
 
Dominic Michaelis
Dominic Michaelis
even though every normal endomorphism is unitar diagonizable
 
Lord_Farin
Lord_Farin
@DominicMichaelis I thought you said that we were in $\Bbb C^n$.
 
robjohn
robjohn
7:28 AM
$$
\lower{5pt}{\Huge\ddot{\smile}}\quad1-\binom{365}{n}\frac{n!}{365^n}
$$
 
Dominic Michaelis
Dominic Michaelis
no it may be infinite dimensional but the scalarproduct is like in $\mathbb{C}^n$
 
Gustavo Bandeira
Gustavo Bandeira
@robjohn Happy the entire year?
 
Lord_Farin
Lord_Farin
@DominicMichaelis But dimension is preserved under isometric isomorphisms.
 
Dominic Michaelis
Dominic Michaelis
yeah my $n$ may be infinite
 
robjohn
robjohn
@GustavoBandeira $1-\binom{365}{n}\frac{n!}{365^n}$ is the birthday problem or the answer thereto
 
Dominic Michaelis
Dominic Michaelis
7:30 AM
sorry for that
 
Lord_Farin
Lord_Farin
@DominicMichaelis But then you get convergence issues. Do you mean e.g. $\ell^2(\Bbb C)$?
 
Dominic Michaelis
Dominic Michaelis
yeah for example $\ell^2(\mathbb{C})$ is a unitary vector space
 
Lord_Farin
Lord_Farin
@DominicMichaelis Is this your definition?
 
Gustavo Bandeira
Gustavo Bandeira
@robjohn There's something I'm curious about and I guess you may know about it.
 
robjohn
robjohn
@GustavoBandeira yes?
 
Dominic Michaelis
Dominic Michaelis
7:33 AM
@Lord_Farin it seems so as i said it is for a friend but that is the one i have in mind
 
Gustavo Bandeira
Gustavo Bandeira
For what reason people became interested in the foundations of mathematics in 19th century and the beginning of the 20th century?
When I read logicomix, it seems that Hilbert had the idea of transforming mathematics in something that a machine could do.
(Or at least some parts of it)
 
robjohn
robjohn
@GustavoBandeira I think it was just an offshoot of the formalization of mathematics via axioms and proofs.
 
Lord_Farin
Lord_Farin
Back in a few, some urgent matters.
 
Gustavo Bandeira
Gustavo Bandeira
I mean - when calculus was invented, it seems people kept using it even with the logical flaws - why to fix it only in the 19th/20th century?
 
robjohn
robjohn
@Lord_Farin put the seat down
 
nerdy
nerdy
7:35 AM
I read that mathematics was finding a lot of paradoxes ( including the fall of euclidean geometry ) and was looking for a firm ground to stand upon
by the 19th century
 
Gustavo Bandeira
Gustavo Bandeira
@nerdy Yes. With Russel's paradox being the most famous example - I guess.
 
robjohn
robjohn
@GustavoBandeira they didn't know it needed fixing before that, or didn't care enough
 
anon
anon
@nerdy the fall of euclidean geometry?
 
nerdy
nerdy
not fall, but development of non-euclidean
?
before that there wa sonly euclidean
was*-
 
anon
anon
yes
 
Gustavo Bandeira
Gustavo Bandeira
7:37 AM
I guess the only things that fallen were the parallel axiom and the lack of notion of betweeness.
 
robjohn
robjohn
@nerdy I wouldn't call it the fall of Euclidean geometry, I'd call it the discovery of Riemannian geometry.
 
nerdy
nerdy
true
 
anon
anon
Euclidean and Riemannian geometry are neither mutually exclusive nor mutually exhaustive :)
 
Gustavo Bandeira
Gustavo Bandeira
@robjohn Is riemannian geometry a evolution of euclidean geometry? I mean, is it possible to solve euclidean problems with riemannian geometry?
 
robjohn
robjohn
@GustavoBandeira I think Riemannian geometry is a generalization of Euclidean geometry (after removing the parallel postulate)
 
anon
anon
7:39 AM
that question is essentially "is it possible to solve things in flat space using differential and integral calculus designed for curved spaces?"
 
robjohn
robjohn
@anon by setting the curvature to 0
 
Gustavo Bandeira
Gustavo Bandeira
@robjohn I've seen the cover of a book on riemannian geometry, and it had a sphere there. Since then I think that Riemannian geometry deals with geometry on spheres.
 
Dominic Michaelis
Dominic Michaelis
@GustavoBandeira nearly it deals on geometry on manifolds ;)
 
Gustavo Bandeira
Gustavo Bandeira
I guess geometry on balls would be perjorative.
 
robjohn
robjohn
@GustavoBandeira ah, that is not true. Hyperbolic and non-constant curvature surfaces are the subject of Riemannian geometry
 
Gustavo Bandeira
Gustavo Bandeira
7:42 AM
I'm thinking about buying this book.
 
skullpatrol
skullpatrol
This is one of the areas of General Relativity where: chat.stackexchange.com/transcript/message/9239749#9239749
 
Gustavo Bandeira
Gustavo Bandeira
It's weird. When I was in high-school, I thought that geometry dealt with cubes and triangles.
Now I've seen people obtaining geometry everywhere - Now I really have no definition for geometry.
 
skullpatrol
skullpatrol
You can just look to the word "geometry" itself: geo means earth and metry means measure.
For the original definition.
IMO
 
Lord_Farin
Lord_Farin
Back.
 
skullpatrol
skullpatrol
Hi
Could you please explain why
42 mins ago, by skullpatrol
@Lord_Farin Are you saying $$arithmetic \neq math$$?
@Lord_Farin
 
Lord_Farin
Lord_Farin
7:58 AM
@DominicMichaelis Yugh I note how far my knowledge of functional analysis has dissipated. There were times when this question would've appeared trivial.
@skullpatrol Consider the negation. It is exactly the primary misconception about mathematics; this misconception needs to be eradicated.
 
nerdy
nerdy
If relations between two sets are just sets and relation have both domain and codomain, are we really talking about domain and codomains of sets ?
 
Lord_Farin
Lord_Farin
8:15 AM
@nerdy Yes. I should add, of sets of ordered pairs. An important distinction.
 
nerdy
nerdy
good point, btw i was thinking
is the cartesian product defined between any set and the empty set ?
for example, consider A a non-empty set, whats A x (empty_set ) ?
 
Lord_Farin
Lord_Farin
 
nerdy
nerdy
thanks
 
 
1 hour later…
Dominic Michaelis
Dominic Michaelis
9:26 AM
@Lord_Farin we "proved" something similar today in theoretical physics assuming that in every eigenspace there are eigenvectors for the other operator too :D
 
Lord_Farin
Lord_Farin
@DominicMichaelis Yes in physics one usually (often even tacitly) assumes all the necessary hypotheses for the result to hold. But as pure mathematicians, we like to examine what assumptions (if any) are necessary.
These things are used all the time, particularly in quantum mechanics.
 
Dominic Michaelis
Dominic Michaelis
yeah in fact he said, assuming it holds we can show it holds :D
 
skullpatrol
skullpatrol
Proof by assumption.^
 
Charlie
Charlie
9:46 AM
@skull @dominic @Lord_F good morning!
 
Lord_Farin
Lord_Farin
@Charlie Good morning to you too.
 
Charlie
Charlie
@Lord_Farin thanks
 
skullpatrol
skullpatrol
@Charlie how are you?
;O
 
Charlie
Charlie
@skullpatrol I'm fine, I didn't sleep well, but I'm fine. And you?
 
Lord_Farin
Lord_Farin
@skullpatrol I might fall prey to that today as well. We're out of coffee :O.
 
Charlie
Charlie
9:49 AM
Actually I'm not fine, I wanted to sleep more...
 
skullpatrol
skullpatrol
@Charlie maybe you can catch a quick afternoon nap?
 
Lord_Farin
Lord_Farin
@Charlie Actually I'm not fine, I want to work on my thesis more.
 
skullpatrol
skullpatrol
@Lord_Farin If you want to work on it, then that is what you should do.
 
Lord_Farin
Lord_Farin
@skullpatrol Thank you @skull, Captain Obvious incarnate :)
 
Charlie
Charlie
@skullpatrol if time allows
 
Lord_Farin
Lord_Farin
9:52 AM
I'm apparently suffering from the human fault to prefer instant satisfaction over long-term profit.
 
skullpatrol
skullpatrol
@Charlie You should try and speed through the first part of your day to make time for it.
 
Charlie
Charlie
@skullpatrol :-/
 
Lord_Farin
Lord_Farin
@skullpatrol Hah. This has unexpected side effects. It fills me with eagerness to work hard through the afternoon so as to earn myself some MSE and -chat instead of grabbing it immediately.
 
skullpatrol
skullpatrol
@Lord_Farin Very few people can discipline themselves to tolerate short-term pain for long-term gain.
IMO
 
Lord_Farin
Lord_Farin
@skullpatrol I will throw out another attempt presently. It includes leaving this chatroom (no afk today; it distracts me too much still). I hope to earn my way back in later today.
Bye @skull, @Charlie, @all.
 
skullpatrol
skullpatrol
10:01 AM
later
 
Charlie
Charlie
@Lord_Farin bye!
 
skullpatrol
skullpatrol
Who is "all"?
:D
 
Charlie
Charlie
;)
 
skullpatrol
skullpatrol
}B-)
 
Charlie
Charlie
Hahahaha
 
skullpatrol
skullpatrol
10:03 AM
:D:D:D:D
 
Charlie
Charlie
:DDD
 
skullpatrol
skullpatrol
:DD
 
Charlie
Charlie
:D
 
skullpatrol
skullpatrol
0
:(
:((
 
Charlie
Charlie
@skullpatrol why??
 
skullpatrol
skullpatrol
10:06 AM
{...-4, -3, -2, -1, 0, 1, 2, 3, 4...}
 
Charlie
Charlie
Integers
 
skullpatrol
skullpatrol
{...:(((, :((, :(, :|, :D, :DD, :DDD...}
Actually the opposite of :D is D: and the opposite of :) is :(
 
Charlie
Charlie
Hahahahs
 
skullpatrol
skullpatrol
:-| = 0
 
Charlie
Charlie
Yep
 
skullpatrol
skullpatrol
10:12 AM
yipyipyip
 
Charlie
Charlie
Yipyipyip
 
skullpatrol
skullpatrol
I saw a new one today >:)
>8-)
 
Charlie
Charlie
;O
@skullpatrol oh
 
skullpatrol
skullpatrol
 
Charlie
Charlie
@skullpatrol I may take a nap now, skull...
@skullpatrol ORLY?
 
skullpatrol
skullpatrol
10:21 AM
@Charlie Yarly
 
Charlie
Charlie
Haha
 
skullpatrol
skullpatrol
"Exclusive To All Newspapers"
 
Charlie
Charlie
Zzzz
 
skullpatrol
skullpatrol
@Charlie see ya later
 
Charlie
Charlie
@skullpatrol see uou soon
 
skullpatrol
skullpatrol
10:22 AM
yipyipyip
 
Dominic Michaelis
Dominic Michaelis
@Charlie hi
 
skullpatrol
skullpatrol
@DominicMichaelis are you ignoring me?
 
Dominic Michaelis
Dominic Michaelis
@Lord_Farin btw we can't reduce it to $f$ does have only one eigenvalue, because this implies the result directly, but we can reduce it to $f$ does have 2 eigenvalues
@skull no, why do you think I ignore you ?
 
skullpatrol
skullpatrol
@DominicMichaelis Just wondering :), I said huhu and you said nothing back...
 
Dominic Michaelis
Dominic Michaelis
@skull i am in university sry huhu to you :)
 
skullpatrol
skullpatrol
10:35 AM
@DominicMichaelis :D
B.T.W. If you do want to ignore me, that's ok too :D
 
Dominic Michaelis
Dominic Michaelis
na thats not it
 
skullpatrol
skullpatrol
np
either way
 
Dominic Michaelis
Dominic Michaelis
tikz doesn't make what i want
 
skullpatrol
skullpatrol
Have you noticed the web page preview on google search doesn't work any more?
I used to be able to glide the pointer over the search results and get a preview of the page...
 
Dominic Michaelis
Dominic Michaelis
10:56 AM
no i didn't notice
 
skullpatrol
skullpatrol
@DominicMichaelis Do your Professors lecture in English?
 
Dominic Michaelis
Dominic Michaelis
it depends on what i listen, to, some lectues are on english some on german
 
skullpatrol
skullpatrol
Math and Physics?
 
Dominic Michaelis
Dominic Michaelis
well physics is on german but some math lectures ar eon english
do you got a latex setup on your pc?
 
skullpatrol
skullpatrol
yip
 
shobon
shobon
11:12 AM
i cant find any questions i can answer :(
 
skullpatrol
skullpatrol
11:22 AM
Make one yourself :)
 
Charlie
Charlie
11:52 AM
Could not take a nap, @skull
Hi @dominic
 
skullpatrol
skullpatrol
@Charlie Why?
 
Charlie
Charlie
@skullpatrol it's hard to take a decent nap when you're not home :'(
 
skullpatrol
skullpatrol
@Charlie Then try and get home early :)
 
Charlie
Charlie
Ooow
 
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