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04:00
Oh, never mind. Misread your comment.
Sorry.
@FenderLesPaul Not just me, do simple math.
Suppose a professor graduates what, 30 students in their career? That means there's a 1 in 30 opportunity for a student to become a prof.
30?
Therefore, it is insane for academia to pretend that everyone should be a prof. Absolutely mind-blowingly ridiculous.
Isn't that a lot?
@0celo7 I don't know, but I don't think so.
@DanielSank right I'm not saying everyone should expect to become professor
that's basically damn near impossible nowadays
04:03
@DanielSank It is quite a lot, yes. But even if you insert realistic numbers your point stands.
I just meant that for a handful of people becoming a professor is the most enjoyable path for them
@MikeMiller Oh is 30 a lot?
I figured something like 1 student a year on average.
But then experimental labs can go through waaaaay more than that.
Yes, that is quite a lot over what the average physics professor does. First, there's the problem that the 'generic' school does not have a PhD program. Ignore that. Then there's just the fact that most professors don't graduate 1 student a year for most of their career. Physics probably does graduate a lot more students than math (I don't have the numbers), but still much less than that.
@MikeMiller Interesting. Right before my PhD advisor left for Google the lab had 20 in it at steady state!
David Awchalom's lab was similarly large.
I figured those kinds of labs would offset the smaller theory shops.
Yeah, I do agree that physics labs are bound to graduate a hell of a lot of people.
04:07
did you guys hear about the professor who was suspended at caltech?
(Whether or not it's 30.)
the astro dude
No, what did he do
too fresh with a freshman?
I hope this isn't some stupid scandal that we should all ignore...
no it was pretty serious and I'm happy he was suspended but he should've been dealt far worse punishments
04:08
did he do differential forms in a freshman class
gender discrimination against female students
two of his students
borderline sexual harassment
what did he do?
And, did the university take appropriate action?
well caltech suspended him for a year, prevented him from coming on campus, and prevented him from communicating with his grad students
but I think it should've been harsher
@0celo7 he fell in love with one of the girls
@FenderLesPaul how sweet
basically forced her out when she didn't reciprocate
she's at Berkeley now
Wow. Um, they didn't fire him?
nope
blows my mind
04:11
Was he convicted of this?
Or admitted to it?
I'm not sure if he admitted but apparently the committee unanimously agreed that he was at fault
and they also had evidence from texts he sent the other girl
>buzzfeed
@DanielSank I would hope that if a university or company comes to the conclusion that harassment happened, the perpetrator is fired before they're convicted of harassment in a criminal court.
Do you have an image/dropbox for that?
@MikeMiller Yes.
I was going to say that. I agree.
04:13
@0celo7 of the webpage?
@FenderLesPaul yah
If you don't want to give them clicks, use duck duck go or whatever.
@MikeMiller Mh, don't care enough
Then go back to your hole.
it basically just has pictures of some of the texts
04:14
I should probably be reading/writing scholarship apps
@MikeMiller ok...
anyways my point is just that
while I commend caltech for taking action
I think it should've been harsher
@MikeMiller Wat?
stuff like this just makes it so much harder for female students to commit to physics
@FenderLesPaul I have decided (in my old age) that issues like this are usually best not judged without full information.
@FenderLesPaul Ok so, I want to talk about something related to this.
@DanielSank ::cough:: Ferguson ::cough::
04:16
@DanielSank you're right I just might be biased in this case because I've personally known female students who have been discriminated against by professors or male peers
@FenderLesPaul doesn't that happen in every field though?
@FenderLesPaul I definitely agree that the physics community, in general, is not friendly to women.
how does one play a game that long
and still be terrible
like absolute garbage!
@0537 I don't see the point of this response. Does that justify anything?
04:17
@0537 sure but that doesn't really change the conclusion
@DanielSank what's the related thing you wanted to talk about?
@FenderLesPaul I decided not to bring it up.
Maybe later.
@MikeMiller Are you familiar with do Carmo's Riemannian geometry book?
I'm aware of it.
@MikeMiller whatever.
04:21
Oh if you haven't read it you can't answer my question. (I'm looking for a specific proof in it.)
(I know how the proof works, but I can't find it in there.)
do Carmo is an ice cream shop
@MikeMiller That's not the point! Logical fallacy alert!
There's a great ice cream place near me called Salt and Straw. I never quite got the name. Is ice cream salty or something?
04:22
It's useful to understand the scope of problems. If nothing else, it gives us an idea of who we can go to for support!
He proves the Theorema Egregium but never showed that the Riemann tensor is an isometry invariant. He just kinda assumes it unless I missed the proof somewhere.
It also helps us understand root causes. If only physics had this problem, we'd introspect. If the problem exists elsewhere, we look for broader causes.
Just like in science.
@MikeMiller do people longboard a lot at UCLA?
It is a dangerous fallacy to reject the question "Does the problem exist elsewhere" as if it were some kind of appeal for justification.
@0celo7: He either said it earlier or thinks it's obvious.
04:24
@MikeMiller Well I read every page and at least looked at every exercise. It's not in there...
OK, then he must think it's obvious.
And it's not obvious, IMO.
@FenderLesPaul I don't think I've seen a single person longboard. I have seen people on these stupid hoverboards.
omg are those hover boards becoming a thing?
There's a specific trick for pulling back the LC connection along an isometry.
@FenderLesPaul They are at my school FWIW.
04:25
Hello my little duckypops
Mostly a black people thing.
@FenderLesPaul Unfortunately, yes.
@Slereah What does that even mean
@FenderLesPaul Cuz, uh, they're neat?
Who knows
04:25
@Slereah Hello snookydorf.
2
Oh you
@DanielSank He did not ask why.
He asked if.
A small German village inhabited by the "Jersey Shore" star.
no one can use them at my school mwahahaha
@MikeMiller Ah. Yes, the whole reading thing...
04:27
@DanielSank Now, since I think it's worth asking: "Why are they becoming a thing??"
Feel free to link the previous answer.
@MikeMiller Uh, 'cuz they're neat?
::shrugs::
Maybe. I still have an urge, which I suspect is part of my very core, to push the users off those stupid hoverboards.
@MikeMiller heheheheh
After, what, eight years of UCSB undergrads on the bike path I some times want to carry a stick to shove into their spokes.
Get a cane.
"Whoops! How'd that get there?"
04:29
Claim you "tripped"
You are an old man after all
But then there's the fact that hurting people is not fun.
@DanielSank This is the sort of measured dialogue it's good to see now and then.
::bows::
@MikeMiller I have been trying to develop some skills in the area of stochastic processes.
That seems like neat stuff.
Give it up that delta function is not defined
04:32
I have a solid mastery of Fourier transforms, and a pretty good knowledge of statistics.
@0celo7 Not talking about that at the moment.
@MikeMiller Yes. I am wondering if you could offer some guidance.
Ah, no.
Ah, too bad.
@DanielSank Forgive me, you've pretty much asked everyone that though :P
@0celo7 It still bothers me that I haven't figured that out.
The closest I've been to stochastic processes is a class on financial math I dropped out of and a result I heard about Brownian motion.
04:34
@DanielSank There's a result in a GR book that I have not been able to reproduce
Been thinking about it for a year
Oofa, I know the feeling.
^ That's actually a neat calculation.
How long have you been working on figuring out why kids love cinnamon toast crunch?
Take a rod and put two sliding masses on it. Connect them by a spring. Let a gravitational wave pass transverse to this system. What is the EoM for the masses?
@MikeMiller Pffft, I solved that in 0.3 ns.
Well, what is it?
04:37
It's because you get to eat a bowl of cinnamon and sugar and call it "breakfast".
@DanielSank Computer man, what's a good speed for a USB 3.0 thumbdrive?
like what should I expect
@DanielSank wrong question
@0celo7 orly?
I asked about a thumbdrive, and I'm asking you
04:40
@0celo7 Sounds like you're the one best suited to google it for you, then.
"Unclear what you're asking"
2 mins ago, by 0celo7
@DanielSank Computer man, what's a good speed for a USB 3.0 thumbdrive?
thumbdrive
@MikeMiller I have to do everything myself around here...
^ LOL
@0celo7 I have no idea. I tried to hide my ignorance with disparaging remarks, but you saw through my ruse.
you're an engineer, don't engineers know stuff like that
I'm a "Quantum Electronics Engineer". That does not indicate expert level knowledge of USB.
04:44
quantum USB drive
@MikeMiller That I can help with.
wait is that a thing?
holy shit
the quantum screen of my quantum chromebook isn't quantum backlit anymore making it basically unusable
I want a quantum vape
@MikeMiller oh so it's a standard quantum computer now
04:45
ಠ_ಠ
hahaha
what's a quantum screen
the photons have to tunnel through an inch of lead to reach your eyes?
It's a regular screen but I wrote the word quantum on the back in sharpie
2
@MikeMiller Heheheheh.
04:58
@DanielSank So can you play Pong on one of your machines yet?
god I love key and peele
who?
@EmilioPisanty and @KyleKanos - I'm very sorry about not noticing the size declaration part in the meta post. So, I'm removing those posts and will post new versions of the same answers only if I'm able to do something about the image sizes.
:)
@0celo7 Yeah, my laptop can run pong.
I am sorry...
but again I do not know what to do...
I will just say that just in case you ever unblock me...
I am truly sorry...
06:03
> An application of the Theorema Egregium is seen in a common pizza-eating strategy: A slice of pizza can be seen as a surface with constant Gaussian curvature 0. Gently bending a slice must then roughly maintain this curvature (assuming the bend is roughly a local isometry). If one bends a slice horizontally along a radius, non-zero principal curvatures are created along the bend, dictating that the other principal curvature at these points must be zero.
> This creates rigidity in the direction perpendicular to the fold, an attribute desirable when eating pizza, as it holds its shape long enough to be consumed without a mess.
 
2 hours later…
07:54
Er...can anyone make sense out of this?
-2
Q: evaluating results produced by a source detector tool (e.g. sextractor)?

orkansextractor finds and outputs catalog of objects in an astronomical image. in order to evaluate results i need to calculate F scores. is there a testing tool for this task? i need to generate binary images from both sextractor output and corresponding object catalogue (ground truth) to find TPs ...

user54412
08:48
um yes
user54412
given an image, he wants a catalog source listing all the binaries in the field, and he wants to know how confident one particular tool is when asked to generate the same list
10:30
0
Q: No More questions to ask?

JenIs there a point where all questions have been asked and no idea is original? Can it be formulated in an equation?

 
2 hours later…
12:02
Do you think the SE chemistry people would get mad if I asked how to distil vomit into hydrochloric acid
user162403
12:19
Hi, I don't understand why the degree of degeneracy of 3d is 6. Could anyone explain it to me ? As l=2 i would say there are only five possibilities for m_l ...
13:47
@Slereah why do you want to do that?
For science
13:57
It is possible, but is it worth it? vomit is just a complex mixture of proteins, debris, HCl, mucus etc.
Then I can sell it as home made bio hydrochloridric acid
...the distillation process would smell like puke :P
Well yes, but then again the puke would smell like puke too
probably the separation process (and the residual waste you need to deal with) will be quite costly for this to be economically viable
My dreams are dashed again
14:56
Genius plan: kidnap someone and torture for years. Collect all the vomit and distill it into HCl. Then dissolve the body in HCl. Literally untraceable.
15:51
@ACuriousMind Will the average physicist understand what "locally homeomorphic to $\mathbb{R}^n$" means?
or should I just say "can locally be mapped to $\mathbb{R}^n$ in a continuous fashion"
If it's GR related I hope he knows what it means
I need a physicist
are there any of those around?
@0celo7 I'm relcutant to say for the "average physicist", but someone reading a post on different index notations in GR should know that
did you check Craigslist
@ACuriousMind you know...intro GR books don't cover that
Hartle, Schutz, Zee type books
15:59
::sigh::
so I'm not sure
Write it, link "homeomorphic" to the appropriate Wiki article.
to explain the whole "why do mathematicans not like coordinates" I have to explain that a chart does not necessarily cover the manifold
right?
also because they hate fun
@ACuriousMind ah, ok
@Slereah $F^u{}_n=G^u{}_n$
16:01
Using $u$ as an index is poor form
@Slereah They like $F_\text{un}$, they're just not sure it exists.
Maybe they know it exist but they cannot construct it
@Slereah ok you can write an answer on my question explaining that
@ACuriousMind "For instance, it can be easily shown that there is no homeomorphism between the line and the circle." Am I allowed to use "easily" there?
Yes, I know how to prove it. Consider the restriction of the homeomorphism to $S^1-\{p\}$.
@0celo7 Does that phrasing add anything over "For instance, there is no homeomorphism between the line and the circle"?
@ACuriousMind Yes. It makes me seem smarter.
@ACuriousMind How would you define tensor field without any bundle or module machinery?
Is it simply a rule that assigns to each point a tensor on the tangent space?
16:08
@0celo7 How would you define a vector field?
@ACuriousMind Section of the tangent bundle...
But it's just a rule that assigns a vector to the tangent space at each point.
Great, I have to define tangent space.
Ughhhhhhh
@ACuriousMind What's your favorite definition for $T_pM$?
Vector space spanned by the derivatives.
@ACuriousMind Do I need to prove that this is truly a vector space?
I don't know, do you? Beware of overburdening an answer with a bunch of auxiliary material that detracts from your main point
The main point is slowly becoming that these people should read a math book...
16:20
It's $R^n$
Is it worth showing it's a vector space
Ugh
You have to work in a chart...
I don't like charts
@ACuriousMind Will the average physicist have an intuitive understanding of why $\operatorname{span}(\partial/\partial x^\mu)$ is the "set of tangent vectors"?
I don't.
I just know I can show equivalence to the curve definition.
I think Wald defines is using derivations, which also has no intuition built in
Unless maybe you're an algebrist
@Slereah What's your definition of the tangent space
Either spanned by curves or a tangent bundle, I guess
How are you defining the tangent bundle?
Fiber bundle with $\mathbb{R}^n$ as the fiber and $GL(n)$ as the structure group, I s'ppose
@Slereah Not enough - you need to express that the vectors in that bundle are actually tangent vectors, and not just some $n$-vectors.
16:31
Hm
What more do you need then
@Slereah Maybe I should just say "cf. e.g. Hawking and Ellis (1973) for a construction of the tangent space"
I vaguely recall something about a link with the coordinate chart
get them used to that early
It is like religion
Don't question it
It's somewhere in the book
@ACuriousMind huh?
how are you defining a tangent vector then
16:33
@Slereah You really need to define $T_p M$ and then form $\bigcup_p T_p M$, I think.
Lemme check Steenrod
@0celo7 Not every vector bundle with fiber of the dimension of the manifold is the tangent bundle, is it?
@ACuriousMind ¯_(ツ)_/¯
@0celo7 Like everyone else - derivation/equiv. class of curves, etc.
yeah yeah
16:35
You know for a physics chat
this chat is almost always filled with boring math
Pretty much
I blame @0celo7
is there such a thing as exciting math
fair point
@Slereah I blame Wald
this is all his fault
@0celo7 dem's fighting words
16:36
If you have physics to discuss tho
Feel free to ask
@FenderLesPaul the man can't use abstract index notation properly
@0celo7 yeah that's true
have you ever read chapter 2 of Penrose and Rindler vol1?
it's the funniest thing I've ever seen
why
16:37
it's literally an entire chapter on the linguistics (syntax) of abstract index notation
pic?
o?
I don't have the book with me but I'll show you later
actually it might be more than one chapter
I might have a legal copy somewhere
it's where abstract index notation was first introduced to the world
but still pretty over the top
it's like ok dude I get it the indices aren't supposed to represent components; I'm not trying to learn a new language
The problem with Wald is that he writes e.g. $\partial_a v^b$ and $\Gamma^a{}_{bc}$
which only have meaning in coordinates
but he writes them in "coordinate free" notation
16:39
yeah it's an abuse of notation that you won't really see anywhere in the literature
so there goes the whole reason for using coordinate free notation out the window
@FenderLesPaul does anyone else even use abstract indices though
Read books in Penrose notation
Straumann pretty much says "imagine them where they should be"
yeah within the GR community it's like half the people use abstract indices and the other half uses the usual notation
but I don't think anyone uses it as religiously as Wald
@FenderLesPaul I've never seen it...
Only in Wald's papers
16:40
unfortunately that's half the GR community
oh šit have to go
there's one example
from the professor I work for and one of his post-docs
but my professor used to be a post-doc of Wald
so he might have been heavily influenced
Hawking uses abc indices but they're not abstract
I think people just switch between abc and $\alpha\beta\gamma$ based on how lazy they're feeling
in the paper I'm currently writing up I'm not paying any heed to abstract index notation
Ah those are abstract.
16:43
like who the fuck has the patience to make sure they keep track of coordinate and abstract indices
there's one guy in my group that gets really mad when people don't adhere to Wald's rules
and also get's really mad when people don't use Neumann-Penrose notation when working with complex quantities in GR
I'm like "dude calm down it's just GR there's more to life"
these people take GR as seriously as people who play LoL take seriously that game
Like QFT
@FenderLesPaul can you explain to me what research is done in AdS/CMT?
I could but I think it would be a lot more instructive and informative for you to look up the research of the following people:
Subir Sachdev (Harvard)
Sean Hartnoll (Stanford)
Gary Horowitz (UCSB)
Dam Than Son (UChicago)
particularly the first and last people on the list
Ok I will.
In fact if you're interested in any kind of hard CMT (including field theoretic aspects of CMT) then I would suggest peering through Sachdev's articles
he's legendary for this stuff
16:58
We guys, I'm a bit puzzled by the close votes here:
0
Q: Heisenberg's uncertainity principle

AmarnathIn the Heisenberg uncertainty principle, $$\Delta x \cdot \Delta p \geq \frac{h}{4\pi}$$ The values of $\Delta x$ and $\Delta p$ are the standard deviations which we get from the probability distribution function of the particle and I heard that it has nothing to do with the measuring instrumen...

(Worst title ever, I know)
uncertainity
lewl
Seems reasonably clear what OP is asking "Does the measurement process have some bearing on the inequality that is the HUP?"
maybe it's been answered before
I would be surprised if it hasn't
The votes are all "unclear"
4 of 'em.

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