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5:11 AM
@ACuriousMind Because a plot with grid lines is significantly easier to read.
 
 
5 hours later…
9:42 AM
I am currently learning the method of image charges, with the classic point charge, conducting plane example. All is well but when I deal with moving the point charge around, it causes a lot of confusion. I don't know why would the potential of the charge be
-k q / d^2 when it's really close to the plane, with d as the initial distance between plane and charge.
One explanation is that the image charge would stay still, but that doesn't explain moving the point charge horizontally wouldn't do work.
 
10:37 AM
@DanielSank I don't think I agree - what grid lines make easier is read off actual values from a graph, but I would say that most figures are intended to display qualitative relationships rather than quantitative ones, and the qualitative relationship is easier to see when there's less visual clutter
 
 
4 hours later…
2:44 PM
Thanks everyone...
I am back with another couple of qtns :)
When we include Chan Paton factors with the open string, the T dual description has fractional winding numbers, why is this so? I understood that this should be so in presence of a gauge field like ~diag($\theta_1,\theta_2$,...) but why would the existence of Chan Paton factors imply the same effect even in absence of the background gauge field?
 
2:56 PM
@ManasDogra I'm not sure what you mean; the open string has a "fractional" winding number if and only if some $\theta_i\neq \theta_j$.
 
Yes, but why in presence of Chan Paton factors?
 
you'll have to be a bit more explicit for me to understand your question, I'm afraid :P
 
"Indeed a string whose endpoints are in the state..." I don't understand why such a phase factor would come due to the Chan paton factor? I understand when it comes from the background gauge field...
Or does this effect arise in presence of a background gauge field only?
 
I think you're misreading that
you need both Chan-Paton and the background flux to get the broken Chan-Paton $\mathrm{U}(1)^N$ theory
 
3:12 PM
Oh, I realized that at the last moment...
What would happen if there was no Chan Paton factors...just a gauge field and a compactified dimension?
There is no U(N) to break...but there should be some observable effect because of the holonomy right?
 
no, a U(1) Wilson line doesn't do anything - note that gauge freedom allows us to choose the value of one of the $\theta_i$ freely - when there is only one, you can just set it to zero
 
Oh yessss....i can gauge it away ok ok
 
3:53 PM
Is there a way in which closed strings may give rise to U(N)?
Via CP factors it isn't possible because closed strings have no "end" to be attached to.
 
4:28 PM
@ManasDogra I don't think so; there's no massless vector boson in the closed string spectrum that could serve as the gauge boson, is there?
 
4:42 PM
What are you talking about? Is this string theory?
 
 
1 hour later…
5:59 PM
@ACuriousMind >:-(
Quantitative numbers matter.
If I draw a log plot, the difference between slope=1 and slope=2 is enormous.
In other news, what does it mean if I ask Mathematica for a FourierTransform[whatever, blah, blah] and it just returns the same text I typed in, i.e. it doesn't actually do the Fourier transform?
 
@DanielSank I'm not saying they don't, but maybe if the actual data matter that's more an argument to make the data itself accessible instead of having to read it from a graph?
or, if e.g. the slope matters, then I'd still prefer they draw some reference lines with given slopes in the graph instead of me having to read it off the grid
 
@ACuriousMind That's like me saying "I would like sprinkles on my ice cream", and you ask "Why?", and I answer "I like the joyous appearance of sprinkles", and you say "Isn't that more an argument to hang fine art in your house?"
Sure, fine art is nice... so are sprinkles.
 
eh, in that analogy you were asking "Why don't more people put sprinkles on their ice cream" and I'm explaining what alternatives people prefer over sprinkles ;P
 
The alternative being "no sprinkles".
Actually no, the alternative being "No sprinkles, but set up a sprinkles store".
Unfortunately, we do not so often give out sprinkles stores with our ice cream, in scientific publications.
 
6:25 PM
Has anyone here ever mispronounced some physicist's or mathematician's name before realizing the correct pronunciation? It took me a year to find out Lie is pronounced Lee
I guess it was all a lie
 
 
1 hour later…
7:41 PM
Imagine Euler
Also probably every ancient mathematician is mispronounced
 
8:10 PM
You raise a good point here
 
 
1 hour later…
9:14 PM
we all have to say Yooler at least once!
 
9:24 PM
oiler is correct?
 
9:36 PM
@Feynman_00 I pronounced Schwarzschild as "Shwart's child" in a GR final presentation (it's supposed to be like "Shvartz-shield")
Prof probably realized at that point I was just learning from the book instead of the lectures
 
9:53 PM
indeed, imo there's absolutely no shame in mispronouncing something you read
 
It's not about shame, it's about realizing it later
 
true
 
I was so disappointed about Lie algebras that time
@SirCumference nice one
 
btw what is the term for what exists between macro and micro?
 
10:59 PM
@antimony it's not as common, but it's meso
 
11:37 PM
@antimony I mean the class had mandatory attendance, so I doubt he wanted to know that I barely paid attention to the lectures
Just that I learn best with a textbook by far
Strikes me as bizarre that grad courses even have mandatory attendance but that's another topic
 

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