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22:00
well at least the critique was on knowledge
knowledge I can fix
creativity or something like that I can't really lol
There was only one question I think I didn't answer as well as I should have though...so I wonder if it was all based on that one answer I gave...unless maybe all the answers I gave were inadequate, but I just don't know. Again, unknown unknowns. XD
you guys know of a good book that goes over Einstein-Cartan theory?
I've been meaning to skim the stuff in Zee related to it, that's about it
hmmm Zee has Einstein-Cartan stuff?
22:16
Wait no hah
That's not just GR with forms :\
indeed it's not
it's more like GR with torsion
using the language of forms
hmmm, maybe I should read some more books on ML
machine learning
22:23
A completely known unknown to me
22:40
machine learning = something something optimization
3
along with a couple other something somethings
23:03
heh
hmmm...it is not at all apparent to me why the integral of a n-form over a n-Manifold is independent of the choice of covering sets and the partition of unity subordinate to that covering...
Wald just says "it can be shown"...without at least giving an intuitive motivation why that would be the case...
:(
I think that's in Lang's advanced calculus or something similar
I can't recall the result
I mean this has to be the case for the integral to be well defined, so I don't doubt it, but I just don't see how intuitively that's the case...-.-
maybe I have the wrong intuitive understanding of a partition of unity
I would bet that's why
23:19
He explains the covering thing on the page before
Just the Jacobian cancelling the change of variables thing
Trying to remember the partition of unity stuff
I think it's the expression
This kind of thing is a real motivation to skip math and just do physics
$\Sigma_\alpha f_\alpha = 1$
It's just pedanticism justifying stuff we know :(
There's a reason why you bring it out
$f_\alpha$ is a smooth function on $O_\alpha$ so I guess the expression $\Sigma_\alpha f_\alpha = 1$ is really saying the $f$'s have to add up to 1 at each point
I kept thinking of it as $f_\alpha$ is one number that weights the different $O_\alpha$
obviously that's the wrong interpretation
23:22
I think it's to make the integrand well-defined on the whole manifold because the $f_{\alpha}$'s are zero off an open set and $1$ on it so $\sum_{\alpha} \int f_{\alpha} \omega$ is now well-defined everywhere or something
yeah I think it's, in parts where the $O_\alpha$ don't intersect, then you have just $f_\alpha=1$ there so it adds nothing
$\int \omega = \int \sum_{\alpha} f_{\alpha} \omega = \sum_{\alpha} \int f_{\alpha} \omega$
then where the $O_\alpha$ do intersect you have $\Sigma_\alpha f_\alpha = 1$...but in points where the $O_\alpha$ do intersect the integral must match between the intersecting subsets so it doesn't matter how you slice that piece using the $f_\alpha$ you will always get the same answer.
understood now :D
just had to type it out lol
If you integrate $\omega$ over a part where two open sets intersect you overcount without including the partition of unity or something
yeah
the partitions of unity make sure you are not double counting
23:32
I think I never realized that before
(So that's why they come up in Stokes' theorem gawd)
23:48
Say you have $N$ strings fluctuating in a box with $N/2$ strings fixed at $(0,0)$ and at $(1,1)$ and the other $N/2$ strings fixed at $(1,0)$ and at $(0,1).$ All these strings vibrate back and forth to create patterns. Has anyone studied these patterns before?
no idea what that means
what specifically don't you understand about it?
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