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4:00 PM
Much incineration ensued.
 
yay, chatjax.
 
@ACuriousMind Many
I'm at home on vacation
 
I may have shed a tear when Momma had to leave her dragons in the basement.
 
I wonder if dragon meat tastes nice ...
2
 
4:09 PM
@Slereah that got me so confused because I didn't read the physics/mathematics sign.
 
user228700
@JohnR: Hello! :-)
 
@Kaumudi.H Hi :-)
Your second week as a student is officially over and ... it's the weekend!! :-)
 
user228700
@JohnRennie ...and I'm as depressed as ever! :-)
 
That doesn't sound ideal ...
 
user228700
No joke, lol.
 
4:14 PM
I think the average physicist knows that math
 
user228700
Hang on.
 
the average mathematician...doubtful
 
@0celóñe7 You mean the maths on the board not the string interactions right?
right?
 
@CooperCape what?
And I'm talking about theoretical folks
 
we talkiin bout different things i presume
oh right
 
4:16 PM
I think there are certain parts of maths that physicists "know" better than the average mathematician
 
yeah that's fair
I read in my book that string theory helped mathematicians understand calabi-yau manifolds
 
Anyone who has seen string theory in any capacity has been exposed to Kahler geometry
As a mathematician I see no reason to learn about it
 
I was about to vote to close as displays insufficient effort
 
Safe exposure limit: 3.2 millikähler
 
oh right, apologies.
that's fair
 
4:18 PM
@ACuriousMind The guy was a Nazi
 
@CooperCape The OP obviously can't be bothered to do even the most cursory of Googles.
 
I just feel like if i can type it out in a min or so I may as well.
 
@0celóñe7 Pretty much, yes.
 
not much effort on my part.
 
@ACuriousMind Random question of the day: any chance you've seen Hardy spaces in your travels?
 
4:20 PM
@CooperCape by doing that you are encouraging people to post lazy questions.
 
@0celóñe7 Mhhhhh, yes, I have "seen" them, recently in fact, but I can't actually remember where :/
 
@ACuriousMind I doubt you've been doing harmonic analysis lately, so complex analysis?
 
Yeah I get your point... I'll leave a comment about researching a bit next time or something...
@0celóñe7 Getting back to calabi-yau/kahler shapes I understand they were created by mathematicians in the first place? Do they have much use in mathematics?
 
In some rather esoteric parts, yes.
 
pure maths, I presume? :p
 
4:24 PM
To me geometry/analysis falls into two categories. People inventing crazy tools to study reasonable things, and people inventing crazy tools to study crazy things.
Kahler manifolds fall into the second category.
 
lol that's understandable
 
@CooperCape if you're interested the book The Shape of Inner Space by Yau is a fascinating popular discussion of CY spaces.
 
Oh okay, thanks :). I'd be interested to read more into them actually
 
user228700
@JohnR: Right, I'm back!
 
Hi again :-)
Did you decide whether to run the marathon at the weekend?
 
user228700
4:33 PM
:-) One of my classmates made a group on WhatsApp and it really blows up at night.
 
WhatsApp? This is something you young people use? :-)
 
user228700
:-)
 
user228700
...in all seriousness though, you do know about WhatsApp, don't you?
 
@Kaumudi.H I've heard it mentioned, but I don't know how it works or what it does.
 
user228700
@JohnRennie Yes, I will go :-) My mum has asked me to buy a pair of running shoes and everything!
 
4:36 PM
Some form of social networking I'd guess.
 
user228700
@JohnRennie Oh, wow, I see. Basically, it is a messaging app.
 
@Kaumudi.H Hooray, we'll be cheering you on. Is it on Sunday?
 
user228700
Haha, thanks! :-D Yes, it's early on Sunday morning.
 
Good luck! :-)
New running shoes though ...
 
user228700
@JohnRennie Hmm?
 
4:40 PM
You will certainly have discovered how well the new running shoes fit after finishing the race :-)
 
user228700
...hmm, OK, I will update you later that day :-P
 
BTW I didn't buy that tablet. It sold for £50, which is about double what I think it's worth - some people have more money than sense.
 
user228700
Haha, I see :-) Next time, perhaps...
 
There is another similar tablet on eBay tonight, but it too looks as if it will sell for a high price. Oh well.
 
user228700
Ah :-/
 
4:48 PM
@JohnRennie Before I go ahead and buy the book do you know how far it goes in depth with the mathematics?
 
But that's OK. I have eaten a huuuuuuuuuge lunch and I'm now feeling sleepy and content.
 
user228700
@JohnRennie Hehe :-) I saw the pictute, before...
 
@CooperCape It might be a sign of the times
there might not be any reasonable things left to study
 
@CooperCape it's a book for the interested amateur, not for mathematicians, and it barely scratches the maths. The book is intended to explain what CY manifolds are and why they matter, but if you're interested in larning about CY manifolds properly this is definitely not the book for you.
@Kaumudi.H what was the hostel dinner like tonight?
 
@0celóñe7 That would be a tragic day.
 
4:51 PM
BTW have you found a local pizza place yet?
 
user228700
@JohnRennie Don't even ask :-(
 
what even is calabi yau
 
@Kaumudi.H Oh, what doesn't sound good.
 
i don't know man
 
user228700
@JohnRennie No :'-( Everything is quite depressing, like I said before.
 
user228700
4:52 PM
I only had two spoons of rice for dinner.
 
@JohnRennie I'll see how I go with this one. Just felt like after I read "The Elegant Universe" I was left with a feeling of 'k gimme some maths'. I'm sure I'd be completely overwhelmed by a proper mathematical description, however.
 
user228700
I've suddenly got lots more to do, the food sucks quite a lot and our seniors as well.
 
@BalarkaSen To my knowledge it's a multidimensional shape that's supposedly the manifestation of the other 6 dimensions curled up according to Kaluza-Klein theory (or something along those lines)
wait not kaluze-klein theory
maybe?
 
@Kaumudi.H well, at least it is the weekend.
 
user228700
It's only like any other day...
 
4:55 PM
And running is good - it generates lots of helpful neurotransmitters.
 
Tries to recall Kaluza-Klein theory from past life
 
user228700
To add fuel to the fire, one of the first friends I made here is leaving to join a different college closer to her home. All is fine and dandy!
 
@BalarkaSen I couldn't tell you anything about it aside from they said something about curling up dimensions.
 
user228700
Anyway, enough of my venting. @JohnR: Have a nice evening :-)
 
user228700
@JohnRennie Ah, back to this :-)
 
4:59 PM
True though. Running generates endorphins.
 
user228700
Yes, yes :-)
 
all i extract from that is i shouldn't run
 
Anonymous
@JohnRennie Is there any counter-example to : "If $\psi(x,t)$ satisfies the time-dependent Schrodinger's equation and $U$ (the potential function) does not depend on $t$, then $\psi(x,t)$ must be separable into $\phi(x)T(t)$" ?
 
user228700
I will let you know if I feel better on Sunday afternoon.
 
Anonymous
4:59 PM
Good luck for the race, @Kaumudi.H :D
 
@Blue Many
We gave you a necessary and sufficient condition for that to be true
 
Anonymous
@0celóñe7 Give one example please...
 
user228700
I believe you and all! :-)
 
user228700
@Blue HEY, thanks! :-)
 
@Blue Take any two of your separable solutions and add them.
 
5:01 PM
^ exactly what SemiC was telling you
But I am not going to intrude on physics
 
@ACuriousMind Unless they have the same energy.
 
Fair enough. Take any two of your separable solutions for which the $T(t)$ is different and add them, then.
 
user228700
I'm off. Have a great 24-hour period!
 
@Blue can then use our criterion to prove it's not separable...
 
Anonymous
@ACuriousMind Right. Got it
 
5:05 PM
I have exams tomorrow and I'm listening to jackshit on youtube
i am gonna die
 
@Kaumudi.H Good night
 
Without people being mad 'cause I don't know things do you use <href...> to do links or...?
 
@ACuriousMind I think this was a weak part in TW3 too -- the main baddie has no character
 
5:43 PM
<a href="www.google.com">Test?</a>
nope
lol
rip
google.co.uk "test?"
<a href="https://www.google.co.uk/">Test?</a>
 
6:08 PM
ugh finally
 
6:26 PM
@CooperCape yeah, the chat doesn't recognize HTML. Only markdown.
 
I figured it out in the end though :P oopsie.
 
 
1 hour later…
8:01 PM
@ACuriousMind scratch that quad rep-cap, make that... quint? I guess
sooooo close now
 
@EmilioPisanty Geez, you're really getting your mileage out of that cone, huh?
 
@ACuriousMind yeah, it's completely ridiculous
d'you know what happens if you run out of trackable badges?
 
Can you run out? Isn't there some repeatable badge you could track?
 
this looks like slim pickings
not that I'm going to get Illuminator or Legendary any time soon
but when you do, what then?
 
gonna have to take the L on the peer pressure one though
 
8:08 PM
@EmilioPisanty I'd guess the tracking window just displays "Congratulations, you've won Stack Exchange".
 
@CooperCape yeah, I've been thinking about which one to sacrifice
 
sad times
could be reaaallly annoying and post a question saying 'downvotes please'
if you were feeling tragic.
 
I guess if, say, this one
-1
A: Motion described by $a=\frac{k}{x^2}$

Emilio PisantyThe problem, like all energy-conserving 1D problems, reduces to quadratures: that is, it reduces to solving a 1D integral. In this specific case (with no centrifugal barrier) that integral is exactly solvable. To get this, you simply repeat the same steps that you do in the work-energy theorem: ...

were to get a couple of downvotes
then I could delete it without feeling all that bad about it
 
@EmilioPisanty I'm now very tempted to upvote it
 
Huh, I actually had an answer with -3. Let's see how long the script takes to award the badge.
 
8:11 PM
@Mithrandir24601 ¯\ _(ツ)_/¯
I would rather get that peer pressure badge before Epic
 
@EmilioPisanty Why?
 
@ACuriousMind 'cause once I get Epic the temptation to get Peer Pressure will increase
but that would wipe Epic from the most-recent-badge
 
I see
 
so... uh... downvotes? =)
I promise I'll give that 1 rep back
where's @0celóñe7 when you need 'im? he'd be on board right away
 
I don't find the answer that bad, though.
 
8:17 PM
=|
-1
A: Rotation matrix for aligning x-axis in an arbitrary direction

Emilio PisantyThere is a very quick and clean way of doing this, which is presented in Building an Orthonormal Basis from a 3D Unit Vector Without Normalization. JR Frisvad. J. Graphics Tools 16 no. 3, 151 (2012). Suppose you have a normalized vector $\vec n=(n_x,n_y,n_z)^T$, and you want a rotation matr...

this one didn't do well, either
and someone disliked this one, for some reason
-1
A: Optical Activity and Quantum Mechanics

Emilio PisantyYes. It boils down to the orientation-averaged polarizability of the molecule, which is a perfectly calculable property of the molecule and it has been accessible to quantum-chemistry methods for many decades. In essence, you take the molecule in its ground state (or in some thermal ensemble, as...

 
@EmilioPisanty what
what do you need
 
@0celóñe7 I want to get the Peer Pressure badge over and done with
 
What does that mean?
 
I need one of those three answers to go from -1 to -3
 
I don't obsess over the main site
 
8:20 PM
though actually
 
@EmilioPisanty I downvotes those
garbage answers
 
@ACuriousMind it doesn't even need to be permanent
 
jk I upvoted them
keep up the good work
 
¬¬
dv → delete → badge → undelete → undv → uv
 
Nope, not gonna help you game the system :P
2
 
8:23 PM
¬¬
you're directly encouraging me to post bad answers?
 
I think I am encouraging you not to care about a damn bronze badge
 
@KyleKanos I really apologize if I came across that way, but I'm not sure I did. If you could give an example of where I changed topics, that would be nice so I could avoid it in the future.
 
@ACuriousMind I don't care about a bronze badge
I care about my trackables dashboard
 
wait, you want people to downvote your answer?
i'll do so, I suppose, but I'm retracting it later.
 
@heather yes
@heather the answer gets deleted anyway
 
8:25 PM
which one? the second one or the first?
 
@heather You can only retract votes for five minutes, or after the answer is edited
 
there you go.
 
c'mon, @ACuriousMind
just pull the trigger
you're Mr Downvote, anyways
 
@EmilioPisanty But I have my standards! If I downvote you for the heck of it, I'll prove everyone right who claims I downvote just because I like to.
You're asking me to tarnish my reputation for your badge tracker ;P
 
8:28 PM
@ACuriousMind c'mon, it's a rambling mess of an answer
it's probably wrong, too
 
@ACuriousMind is serial iocotring allowed?
*uovoting
*upvoting
 
Go home, you're drunk :P
 
@ACuriousMind there needs be no textual evidence that you did so ;)
just coincidence, that's all...
 
@ACuriousMind I did have some vodka but that's unrelated
 
@0celóñe7 No, serial voting in either direction is not okay, and will be reversed by the system if detected
 
8:32 PM
@EmilioPisanty I will upvote every single one of your answers
 
> In the 2014 film Interstellar, why does the spacecraft Endurance spin? I think it really has to do something with physics?
 
And make socks to upvote you
 
@ACuriousMind what's the system limit?
 
@0celóñe7 Nice try.
 
8:33 PM
@ACuriousMind that doesn't sound like an answer
 
Honestly, I couldn't even tell you if I wanted to because there's no need for mods to know that, so we don't
 
@0celóñe7 that's fine, I'll just bounty the rep away
 
@0celóñe7 I actually talked to a community moderator about that
but i am not sure if i should reveal the information here
 
@BalarkaSen hey @BalarkaSen can I borrow 1 rep from you?
@BalarkaSen you shouldn't
 
meh, im gonna do it anyway
CM told me it's over 9000
 
8:36 PM
@EmilioPisanty prepare to get 9000 rep
 
great minds think alike, see
 
@ACuriousMind will my account get deleted for serial upvoting?
 
@0celóñe7 hmmmm. 500 rep per bounty, three simultaneous bounties allowed, can't close bounties within the first 24 hours. Needs six days to get rid of, then.
 
@0celóñe7 No (accounts only get deleted if they're socks, basically). But serially voting on another user after you have been told you shouldn't do that is something accounts can get suspended for.
@EmilioPisanty Don't tell me you wouldn't keep enough to stay ahead of me
 
@ACuriousMind I already don't
I could be ahead of Rod Vance but I choose not to
 
8:41 PM
@EmilioPisanty how close are you to the rep cap for the day?
 
@heather hit it a couple of hours ago
the cone visibility answer thing hit the roof for the fifth day in a row
=|
 
so you have to wait until tomorrow to reach the epic badge?
@EmilioPisanty oh yeah, I saw that on HNQ
 
@heather that's if I hit the rep-cap tomorrow
which is about as big as ifs get
 
@EmilioPisanty Yeah, but having more rep than me and actually actively giving it away and put yourself behind me is a rather different action than giving it away when you're already behind.
 
@ACuriousMind hmmmmm. good point
 
8:43 PM
@EmilioPisanty well, let's see, 200 rep = 20 upvotes on answers. now if you grab four people to upvote five answers each over the course of the SE day...=P
 
but
@ACuriousMind you were behind me to begin with. I'm not sure when you overtook me.
@heather that would be SE vote fraud
I can make Epic without shenanigans
 
yes, well.
 
just wait until the next ridiculous HNQ to roll along
=P
 
true, those seem to come along often enough.
 
@EmilioPisanty Surely your repertoire of SEDE queries can figure that one out?
 
8:44 PM
i remember when that woodcut/venus moon question came along - got a heck of a lot of rep from that.
 
@ACuriousMind that one's probably pretty darn challenging
it's at the edge of the SEDEable envelope, if not outside it
@heather oh, yeah, I remember that one
btw @heather you actually put Mercedes' thesis on your profile? that's awesome.
 
Howdy
 
@SirCumference howdy
 
@heather I've actually met Mercedes, once (if I'm remembering right) - Pete Shadbolt was doing a talk - he was really, really good :)
 
can I borrow 1 rep from you?
 
8:53 PM
@EmilioPisanty Uh, sure
 
@SirCumference I promise I'll give it back straight away
 
I think I should read it first :P
 
@SirCumference it's going the way of the dodo
I would like it to go with a -3 instead of a -2
 
Never downvote without reading
 
@Mithrandir24601 yeah, Pete Shadbolt is also really good
 
8:56 PM
@SirCumference Good man
 
@EmilioPisanty He's absolutely brilliant when it comes to doing talks
 
@Mithrandir24601 that I haven't seen
 
@ACuriousMind Downvoted for using $dt$ instead of $\mathrm{d}t$
 
@heather you might be interested in this: arxiv.org/abs/1607.08535
3
 
@SirCumference Good man.
 
8:58 PM
I think he may well have given a Wednesday-breakfast informal talk at some point when we coincided at Imperial, but those blur into each other
@SirCumference thanks =)
 
>\mathrm{d}t instead of \mathrm dt
 
@AccidentalFourierTransform synonymous.
 
@ACuriousMind ಠ_ಠ
 
@Mithrandir24601 oh, he's optimistic alright
 
@EmilioPisanty yeah, but -1
 
8:59 PM
@EmilioPisanty he was around at the beginning of the year, so gave us a talk on LOQC (he has really close links with Bristol) and the various problems that it faces. He was so good, that we got him to come back a few times :)
 
@AccidentalFourierTransform -1 on his -1?
 
no, I meant that -1 character
in the spirit of golf.SE
 
@Mithrandir24601 wait, what?
Pete Shadbolt having close links with Bristol?
yeah, you don't say =P
 
\mathrm dt is obviously better than \mathrm{d}t
> We all know that earth is spherical having two poles. If i fly aeroplane from its any one pole in a straight line without approaching escape velocity will it go to outer space??
answer pls
 
@AccidentalFourierTransform Less mocking, more reviewing, please.
 
9:02 PM
@Mithrandir24601 speaking of big T
 
I have 1994 reviews and im staying there forever
 
looks really good
 
no more close votes from AFT
 
@AccidentalFourierTransform after all that anonymity, did you just reveal your birthdate?
 
my age was known
 
9:02 PM
huh
 
Aug 5 at 10:36, by AccidentalFourierTransform
- my parents, 23 years ago
Apr 21 at 20:29, by AccidentalFourierTransform
no, unless you're 22
 
@EmilioPisanty He had me at "Deceptively vague jargon and analogies are avoided, "
 
@ACuriousMind he's really good at that
@Mithrandir24601 actually
that's pretty posh
 
I mean, we're told that he's extremely good at physics, but having no experience of that, all I can say is that he's brilliant at talks
 
@Mithrandir24601 this is Terry or Pete you're talking about?
 
9:09 PM
@EmilioPisanty Pete. I'm sure Terry's really good as well, but I've never actually met him
 
@Mithrandir24601 Terry's an excellent speaker, too
lemme find his inaugural lecture
CC @heather
 
9:25 PM
the measure of the pedagogy of physics is not invariant!!
btw Peierls is the shit
 
Which one is Peierls
is it deformation QM
 
hmm I dont think so
it is classical
> Achieving escape velocity from Rarth
-2
A: Space vacuum power

KyleNot testable or observable, dont waste your time, research flat earth and realise the lies, the guys giving you the answer is full of sh1t.. Pretending to know something he knows jack about.. Funny sheeple..

 
10:27 PM
Wait... what's Rarth? Or is that earth with a sprinkling of arrrr?
 
10:47 PM
@ACuriousMind regrding your question: What is $Q$ supposed to be? Are $X$ and $W$ CY three-folds? Which 3-manifold is $Q$, in that case? Any closed 3-manifold?
 
@Danu $Q$ is...just the base for the fibration, a real 3-manifold (a special Lagrangian cycle in $W$ in the case of CYs with mirrors, if I read the literature correctly). $X$ is a $G_2$ manifold and $W$ a CY 3-fold, as I already write in the question.
 
@ACuriousMind What's a special Lagrangian cycle? I know what a Lagrangian submanifold is...
I didn't know the dimension of $W$ but I should've figured it out from that of $X$ :P
What's a coassoc. 4-cycle?
Are you usng the word "cycle" instead of "submanifold"?
 
@Danu I think it's just a Lagrangian submanifold. The "special" may or may not refer to it being "rigid", which may or may not refer to it having no non-trivial deformations. I find the articles pretty confusing :P
 
And a coassoc. 4-cycle is... One whose tangent space at $p$ is the complement of an associative subspace of $T_pX$?
 
@Danu It's a cycle/submanifold for which the Hodge dual of the 3-form that determines the $G_2$ structure is a calibration form
@Danu Yes, pretty much
 
10:53 PM
I never got around to reading that Harvey & Lawson paper so I don't know what a calibration form is. Is it when that 3-form takes its maximal value or something?
 
@Danu A submanifold is calibrated under a form if the restriction of that form to it is the same as its volume form.
 
Yeah, ok
OK, so what exactly is the problem? Do you understand how to somehow replace a $T^3$ with a K3?
 
@Danu Yes, replacing a $T^3$ by a K3 is a standard duality between heterotic string theory and M-theory
 
So what stops you from doing this fiber by fiber?
 
Well, I don't really understand what that means
 
10:58 PM
So for each fiber independently, you know how to do it
Once you have done this fiber by fiber, what is your problem? Seeing that the result fits together in a nice fibration?
 

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