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11:01 PM
@0celo7 can you tell me how you make the arrow that indicates to which question you refer? The arrow on the left side of the comment.
 
@Sofia Click on the arrow that appears when you hover over a post
 
@0celo7 yeah but pullbacks work between different dimension manifolds as well www-personal.umich.edu/~wangzuoq/437W13/Notes/Lec%2023.pdf
 
@bolbteppa Sure, but my point is that $\alpha$ needs to be defined on the manifold after contraction in order for it to be pulled back.
 
Are you still saying it is not?
 
11:17 PM
@0celo7 I didn't understand you. My question was how do you make the arrow appear and indicate the question to which you answer?
 
"Let M be an n-dimensional smooth manifolds." typo on first line.
 
@bolbteppa I'm saying it's not equal to $\alpha$ if the after manifold is different.
@Sofia You click the arrow on the post you're responding to to get a drop-down menu.
 
@0celo7 let's see. When I click the arrow, there appears "flag to the moderator".
 
I still have to post my question on the perpetual motion holder.
 
11:21 PM
@0celo7 @0celo7 Aaaa! I see something.
 
@Jiminion Please, no perpertual motion. They're not strictly off-topic, but I believe almost everyone hates them.
 
@0celo7 Aye! It worked. Thank you.
 
@0celo7 you are literally saying that if the $f$ in $f : \mathbb{R}^n \rightarrow \mathbb{R}^n | \vec{x} \mapsto f(\vec{x})$ is such that $f(\vec{x}) = 0$ then this means $\mathbb{R}^n = {0}$
 
@ACuriousMind It's a real gadget, but not actually perpetual motion.
 
It's never actually perpetual motion :P
 
11:23 PM
Well not this anyway. It was just named that.
 
'kay then :)
 
@bolbteppa Do you mean $\mathbb{R}^n=\emptyset$ or $\{0\}$?
 
@0celo7 $\{0\}$, the point $0$ in \mathbb{R}^2 is completely different from the point $0$ in \mathbb{R}^3 and neither are elements of a zero-dimensional manifold, they are just points in a space of $n$ dimensions
 
@bolbteppa But if you are contracting $\mathbb{R}^n$ itself (to a point), how does it make sense to talk about the origin like it's still in $\mathbb{R}^n$?
 
@KyleKanos , @dmckee , @DavidZ there are too many posts with no accepted answers, but with comments that in fact answer the question. When I see such comments I send to the commentator an advice to transform the comment into an answer. But I insist that you proceed the same way, i.e. send messages to users to transform their solving comments into an answers. I pass sometimes over apparently unanswered questions, and need to read a whole correspondence for finding out if it is answered or not.
 
vzn
11:40 PM
> It remains a mystery how black holes could have grown so huge in such a relatively brief time after the dawn of the universe, researchers say.
> "This is quite surprising because it presents serious challenges to theories of black hole growth in the early universe," said lead study author Xue-Bing Wu, an astrophysicist at Peking University in Beijing.
 
@0celo7 contractible is a property of functions it does not affect the actual sets, that's kind of all I can say, you use functions to analyze contractibility, you can't actually deform sets the intuitive way you're thinking so you have to use functions to say these things and use loose language.
 
@bolbteppa I get it now. Thanks for clearing that up.
 
Cool
 
I would be very interested if someone would solve this problem. I understand it but I don't know the matrixes $\gamma$. And, moreover, what is $\gamma_5$.
 
11:55 PM
@Sofia They are the Dirac gamma matrices
 
@bolbteppa of course, but I am not used to work with them - a lacune in my knowledge.
 
@Sofia which problem?
 

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