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bolbteppa
bolbteppa
00:00
Is there a way to remember whether to define the EM tensor as $F^{i0} = E^i$, $F^{ij} = - \varepsilon^{ijk} B^k$ or whether to define it as $F^{i0} = E^i$, $F^{ij} = \varepsilon^{ijk} B^k$ or whether to define it as $F^{i0} = - E^i$, $F^{ij} = - \varepsilon^{ijk} B^k$ or whether to define it as $F^{i0} = - E^i$, $F^{ij} = \varepsilon^{ijk} B^k$?
peterh
peterh
@EmilioPisanty My original intent is to give the people a help line, whose question was about physics on the common sense, but not on the site rules. From the point of this intent, the exact wording of the close reason is not important. To have a consensus behind any wording is important.
bolbteppa
bolbteppa
00:28
Incredible physics.stackexchange.com/a/87193/25851
David Z
David Z
01:25
@peterh Moderators can change close reasons; it requires a CM to establish a migration path to another site.
 
2 hours later…
peterh
peterh
03:25
@DavidZ Thanks!
 
4 hours later…
John Rennie
John Rennie
06:55
@BalarkaSen that's a somewhat eccentric precis.
 
1 hour later…
user228700
08:18
Morning!
Kenshin
Kenshin
hello
how did the nerdfighters date go @Kaumudi.H?
user228700
@Kenshin x'D 1) I don't believe it was s'posed to be a date per se, 2) It was scheduled for June and 3) I'm not going.
Kenshin
Kenshin
oh why aren't u going for
user228700
In the first place, I think it's a bit weird, the whole thing; we both know very little about each other and I think he hopes that we can get to know each other quite intimately while I don't.
Kenshin
Kenshin
lol what makes you think that?
cos he's a guy?
and by intimately you mean intimately?
user228700
08:24
@Kenshin No. I mean that he hopes to grow close as friends/other.
user228700
@Kenshin 'Cause he told me.
Kenshin
Kenshin
oh, why don't u want to be better friends?
user228700
I, erm, I know next to nothing about him, he's much older than me and I have no intentions of making intimate friends online.
Kenshin
Kenshin
oh yeah that makes sense
I think like a group nerdfighters thing would've been much betta
user228700
In the second place, my mom agrees and told me that I shan't go :-P
Kenshin
Kenshin
08:26
lol
user228700
@Kenshin Yes, it would be great!
user228700
He's as old as you, actually. I wonder why he wishes to make intimate connections online but oh, well...
Kenshin
Kenshin
how old is he/
user228700
25.
Kenshin
Kenshin
oh yeah
too old bro
user228700
08:28
@Kenshin Well, yes of course, for dating but I don't know what he wants. Anyhoo.
Kenshin
Kenshin
yeah he just wants friends
u said
@Kaumudi.H online helps ppl with like minds to connect
this can be harder in real life if you have a rare mind
user228700
@Kenshin Right, which is why I absolutely love to be part of communities with the same/similar passions as me but this one on one intimacy thing is...erm, no, thanks.
Kenshin
Kenshin
did he use that word, intimacy?
cos that means like doing it
but yeah I'm with ya on this one
user228700
@Kenshin Haha, no, he didn't use that word and I also mean it in the normal sense.
user228700
@JohnR: Hi! :-) Only one more week to go woohoo!
John Rennie
John Rennie
08:47
@Kaumudi.H the end is in sight!!
user228700
More so now than ever before! A week! :-D
user228700
This time next week, I will be...sheesh, I don't think I'll know what to do with myself.
user228700
I'll be going back to Kerala for 10 days though.
Secret
Secret
Why do we all feel so busy? Because we think it is costy to relax ourselves due to all that winner takes all mindset and competition arms race
(and no this is from the economist, I have decided to cut down the number of links I share here in response to recent advice. But this one is worth a read, even if very lengthy. Perhaps, it will help us all to find some of the lost leisure time)
The world will be a better place if we understand the correct attitude we should have in face of time
John Rennie
John Rennie
@Kaumudi.H take your pushbike! :-)
user228700
08:58
How though? I'll be going by train.
John Rennie
John Rennie
Can't you take a bicycle on a train?
In the UK you can't just wheel the bicycle into the carriage because there isn't room, but there's usually a special compartment where you can leave a bicycle.
user228700
@JohnRennie Hmm, I'm not sure if this can be done here.
Slereah
Slereah
In France there's a limit of one bicycle per train car
user228700
In any case, I won't be stuck at home this time! There will lots of travelling via train and car to visit other places.
Secret
Secret
user image
John Rennie
John Rennie
09:02
@Kaumudi.H it's worth asking ...
user228700
I think we're going to my father's place and then to Munnar as well.
user228700
@JohnRennie Ask to take my bicycle?
Secret
Secret
Bottomline (I think?) : Why we are always busy=Illusion of rising scarcity due to overcompetition in our economic systems, and also actual scarcity due to declining natural resources resulting in rise in cost in most areas
Avantgarde
Avantgarde
Munnar is so nice
user228700
@Avantgarde Ooh, have u been?
Avantgarde
Avantgarde
09:03
yeah, long back
John Rennie
John Rennie
@Kaumudi.H yes, check on the train company web site, or ring and ask.
user228700
But I'm only going to be at "home" for a day. We're going to go to several other places as well.
user228700
...and carrying my bicycle around to all those places will be exhausting and unnecessary, really. I won't be cycling around Munnar for sure :-P
John Rennie
John Rennie
@Kaumudi.H Ah, OK, it's not like the last time you were there then? When you were stuck at your grans house with nothing to do?
user228700
No, not at all :-)
user228700
09:06
It will still be quite boring but I think I'll just take a bunch of books to read while travelling.
Avantgarde
Avantgarde
true physicist right there
John Rennie
John Rennie
@Kaumudi.H: BTW I went to an Indian restaurant last night
user228700
Ooh, nice! What did u have?!
Avantgarde
Avantgarde
Let me guess, you had saag and paneer?
John Rennie
John Rennie
Silly name though
Avantgarde
Avantgarde
09:07
or chicken tikka masala
user228700
Ooh, fancy (schmancy)!
John Rennie
John Rennie
@Kaumudi.H hang on, let me check exactly what it was ...
Hyderabadi Gosht
Diced lamb cooked with ginger, garlic, coriander, peppercorn & whole red chilli, finished
with hyderabadi sauce.
Avantgarde
Avantgarde
ah, did you like it?
John Rennie
John Rennie
And my friend had:
King Prawn Harapyaz
King prawns sauteed with ginger, black pepper, green chilli and spring onion.
user228700
@JohnRennie Ah, nice. Was it good?
Avantgarde
Avantgarde
09:10
Now I'm hungry
user228700
Say, how did he/she/you pronounce harapyaz? :-P
John Rennie
John Rennie
@Kaumudi.H Both meals were really nice. I'm unconvinced they bear much relation to anything you'd actually eat in India. I suspect they're tailored to British tastes.
user228700
Right, right. What did u have for dessert?
Avantgarde
Avantgarde
Possible
John Rennie
John Rennie
My friend didn't attempt to pronounce Harapyaz - he just pointed to it on the menu :-)
user228700
09:11
x'D But how would you pronounce it?
John Rennie
John Rennie
As it's written ...
Avantgarde
Avantgarde
hara-pyaz means green-onion literally
John Rennie
John Rennie
hara as in harass and pyaz as in, erm, I can't think of an English equivalent.
Avantgarde
Avantgarde
:P
John Rennie
John Rennie
@Avantgarde aha, thanks. It did have lots of onion in it, and it was green ...
user228700
09:13
@JohnR: I'm looking at the menu and wow, very few vegetarian dishes!
John Rennie
John Rennie
Vegetarianism is a minority pastime in the UK.
user228700
@JohnRennie Ah, I see...
John Rennie
John Rennie
In most restaurants the vegetarian dishes are something of an afterthought, though there are of course restaurants that specialise in vegetarian food.
Avantgarde
Avantgarde
You a vegetarian, Kau?
user228700
Yep.
Slereah
Slereah
09:15
I don't eat animals, only human flesh
Wald's method of doing non-linear operators in QFT on curved spacetime is fairly involved
Avantgarde
Avantgarde
which paper? or the book?
Slereah
Slereah
arxiv.org/pdf/1401.2026.pdf
user228700
Oh, no, my connection to the internet is crumbling!
Slereah
Slereah
a lot of wavefront sets and algebra
user228700
Oh, JB is in the country today!
Avantgarde
Avantgarde
09:22
Seems like a nice, math-intensive paper for QFTCS. Thanks, might have a look
Slereah
Slereah
it is
Although you might want to read a few of his other papers beforehand
Since he references a few
Avantgarde
Avantgarde
Got it
You going, Kau?
Slereah
Slereah
"On the renormalization group in curved spacetime", "The formulation of quantum field theory in curved spacetime" and "Local Wick polynomials and time ordered products of quantum fields in curved spacetime"
Spoiler : normal ordering doesn't work in curved spacetime
user228700
@Avantgarde Hahahaha, nope x'D
Avantgarde
Avantgarde
These 3 are cited in the review too, right?
Slereah
Slereah
09:26
Who knows
it's a big old bibliography
He also references the hamburger problem
the most delicious problem
Avantgarde
Avantgarde
lol what is that
Do you want to, kau?
Slereah
Slereah
Hamburger moment problem
In mathematics, the Hamburger moment problem, named after Hans Ludwig Hamburger, is formulated as follows: given a sequence { mn : n = 1, 2, 3, ... }, does there exist a positive Borel measure μ on the real line such that m n = ∫ − ∞ ∞ x n d μ ( x ) ? {\displaystyle...
Avantgarde
Avantgarde
The guy's surname was Hamburger! haha
user228700
@Avantgarde It's a bit weird that u refer to me using "kau" but no, I certainly don't want to go.
Slereah
Slereah
The descendant of many a Hamburg citizen, one assumes
Balarka Sen
Balarka Sen
09:29
@JohnRennie It's true!
Secret
Secret
Where is balarka sen, I need someone to talk about art,

*3 seconds later* O here he comes
Balarka Sen
Balarka Sen
Did you read MS Fnd In a Lbry?
Avantgarde
Avantgarde
@Kaumudi.H What about Kaumudi? I was using shorthand notation lol.
John Rennie
John Rennie
@BalarkaSen Raskolnikov kills one person. Yes he does compare himself to Napoleon but the context is about the moral issues in taking human life not about Napoleon.
Balarka Sen
Balarka Sen
He kills two, doesn't he? I know, I was just trying to be funny.
The motivation behind killing is to see if human choice can be put to the limits of moral and ethical standards.
John Rennie
John Rennie
09:32
Just the old woman - unless I've misremembered the book (which is certainly possible).
Balarka Sen
Balarka Sen
He also kills her sister because she stumbled upon the scene by accident.
Slereah
Slereah
user image
John Rennie
John Rennie
@BalarkaSen ah, yes, you're correct and I had forgotten about the murder of the sister.
Balarka Sen
Balarka Sen
what a fantastic piece of novel tho
John Rennie
John Rennie
@BalarkaSen Yes I did. I had read it before. I started reading SF in the early 70s so I've read a lot of the stories from the 60s and 50s. That was in the days when the volume of SF published was small enough that you could still read most of it!
@BalarkaSen meh, angst isn't really my thing.
Balarka Sen
Balarka Sen
09:38
I suspected that you are a sci-fi buff. Cool, good to know you read it :) Hal Draper is a Marxist socialist, so it's certainly interesting when he writes a science fiction short story (clearly satirical) so I gave it a read
I thought it was very good.
John Rennie
John Rennie
@BalarkaSen yes, it's well written and for its time the idea was clever. At that time computer databases were still mostly science fiction and the metadata problem hadn't reared its head. So it was well anticipated.
user228700
Raskolnikov felt sick but he couldn't say why,
When he saw his face reflected
in his victim's twinkling eye
Some things you'll do for money, and some you'll do for fun
but the things you do for love are gonna come back to you one by one
Balarka Sen
Balarka Sen
True, I agree.
@JohnRennie Hahah. Well, it's not all teen angst. I like Dostoyevskii because the constant logical dialectics and the paranoid downward spiral of the interpersonal relationships breaks my brain.
He really knew what was coming in Russia in the next century.
Secret
Secret
vimeo.com/59939126
John Rennie
John Rennie
@Kaumudi.H come back to you in a good way I hope :-)
Balarka Sen
Balarka Sen
09:43
(I like him better that Tolstoy tbh)
user228700
@JohnRennie Sheesh, nobody would hope otherwise!
John Rennie
John Rennie
@Kaumudi.H it's just that I find the way it's phrased a bit ominous. It sounds like your sins coming back to haunt you
Should I buy this laptop?
Balarka Sen
Balarka Sen
I like the idea that the things you do for love are sin.
user228700
Haha, I see. I s'pose you'd feel differently if you looked at all the lyrics.
user228700
@JohnRennie Again, why?
John Rennie
John Rennie
09:45
I have been looking for a laptop like that for a while, and this is exactly what I was looking for, apart from the mnior damage.
But it seems a little pricy, given the damage, and I don't really need it - I just want it :-)
user228700
Ah, good to know that you've made that distinction! :-P
John Rennie
John Rennie
Where's @BernardoMeurer when you need him? I need someone to say Go ahead John buy it NOW! :-)
user228700
:-P Sorry.
Balarka Sen
Balarka Sen
Go ahead John buy it now.
There.
John Rennie
John Rennie
You don't count, you're not a computer nerd! :-)
user228700
09:49
Ouch.
John Rennie
John Rennie
@Kaumudi.H Ouch? Is it an insult saying someone isn't a computer nerd?
Balarka Sen
Balarka Sen
i don't like technology. although i'd be really interested if you had videodrome for me...
nah
user228700
@JohnRennie Haha, I s'pose it would depend on the person in question, whether they'd take that as an insult or not.
John Rennie
John Rennie
@BalarkaSen A Videodrome download is only a short google away if you really want it. Not that i condone this of course.
On that topic, a friend's daughter is working on the current Blondie tour.
Balarka Sen
Balarka Sen
I want the tapes tho. The ones that gives you uncountrollable brain tumor.
I don't know Debbie Harry but she acted well
John Rennie
John Rennie
09:52
Ah, OK, I can't help there. You could ask Koji Suzuki.
Balarka Sen
Balarka Sen
Ah? Who's that?
John Rennie
John Rennie
Ring (Suzuki novel)
Ring (リング, Ringu) is a Japanese mystery horror novel by Koji Suzuki first published in 1991, and set in modern-day Japan. It was the basis for a 1995 film (Ring: Kanzenban), a television series (Ring: The Final Chapter), a film of the same name (1998's Ring), and two remakes of the 1998 film: a South Korean version (The Ring Virus) and an American version (The Ring). == Plot synopsis == After four teenagers mysteriously die simultaneously in Tokyo, Kazuyuki Asakawa, a reporter and uncle to one of the deceased, decides to launch his own personal investigation. His search leads him to "Hakone Pacific...
Balarka Sen
Balarka Sen
ahh right
user228700
Ed Sheeran is coming to Mumbai OMG OMG OMG.
John Rennie
John Rennie
Gujarati Girl?
user228700
09:58
:-P
user228700
I have to go (to the concert).
John Rennie
John Rennie
See, I'm cool, I've listened to his new album (though only because my niece put it on in the car and refused to turn it off even under torture).
Kenshin
Kenshin
Ed sheeran has too many songs
John Rennie
John Rennie
@Kaumudi.H Yes, I should probably get back to work. See you later.
Balarka Sen
Balarka Sen
@JohnRennie I am sorry for you
user228700
10:00
@JohnRennie Oh shush, his new album is not so bad.
user228700
@JohnRennie :-P I meant to have to go to the concert, not like, you know, now.
Balarka Sen
Balarka Sen
i should listen to Joy Division at some point
John Rennie
John Rennie
@BalarkaSen It was a traumatic experience - I may never fully recover.
Balarka Sen
Balarka Sen
:(
John Rennie
John Rennie
I might make an offer on that laptop and see if the seller accepts it. What should I offer? £300? £325?
user228700
10:01
user image
Kenshin
Kenshin
What laptop
Balarka Sen
Balarka Sen
chill and have a vodka comrade
Kenshin
Kenshin
who is communist?
John Rennie
John Rennie
18 mins ago, by John Rennie
Should I buy this laptop?
user228700
@Kenshin These people who supposedly hate Ed sheeran.
Balarka Sen
Balarka Sen
10:04
we work for the collective dictatorship of the proletariat, that's all
Kenshin
Kenshin
wtf is proletariat
Balarka Sen
Balarka Sen
the neobourgeois are unwelcome
@Kenshin you should learn some marxist terminology
v v v useful
Kenshin
Kenshin
lol why marxism is terrible
user228700
Signed up on several different websites to be among the first few (thousands, I'd guess!) to know when the tickets go up for sale. Can't wait for my "Spam" folder to start exploding!
John Rennie
John Rennie
I went to see his brother Sheep Sheerin'
Kenshin
Kenshin
10:07
goodl uck kaumu
do u live near mumbai
Secret
Secret
where I can check what -ism I am?
user228700
@Kenshin Nope :-/
Kenshin
Kenshin
oh well, excuse to travel
@BalarkaSen what ism am i
Secret
Secret
@BalarkaSen Same question as Kenshin
Kenshin
Kenshin
@Secret u r organ
Secret
Secret
10:09
not funny, too trivial
Balarka Sen
Balarka Sen
@Kenshin you gotta gimme some of that drugs you take! i like that sentence
Kenshin
Kenshin
mate they're too expensive
only for capitalists
Secret
Secret
I don't take drugs, yet I have thoughts more wild than drugged people, WTF?
Balarka Sen
Balarka Sen
i don't think i am an avid enough fan of anybody to go to a gig by anyone even if it's a block apart from my home
Kenshin
Kenshin
lol
Balarka Sen
Balarka Sen
10:10
@Kenshin oops
Kenshin
Kenshin
lol
Avantgarde
Avantgarde
JB has a song or two that are nice-ish
Kenshin
Kenshin
yeah JB FTW
Balarka Sen
Balarka Sen
lumpen bourgeois
Kenshin
Kenshin
can u pls speak more dumbed down
Balarka Sen
Balarka Sen
10:13
all you have to know is whenever you feel another person has different tastes and opinions than you, he's a lumpen bourgeois
Kenshin
Kenshin
lol ok cool
John Rennie
John Rennie
@Avantgarde JB?
Avantgarde
Avantgarde
Justin Bieber
Kenshin
Kenshin
sarcasm right @JohnRennie
user228700
@JohnRennie Performing in India today.
Secret
Secret
10:14
en.wikipedia.org/wiki/Lumpenbourgeoisie\
John Rennie
John Rennie
@Avantgarde I wish I hadn't asked now ...
Avantgarde
Avantgarde
lol
Balarka Sen
Balarka Sen
yeah who's Justin Bieber?
Kenshin
Kenshin
wow he's in india
Avantgarde
Avantgarde
have you seen that video where in an interview, ozzy osbourne is asked about justin?
Balarka Sen
Balarka Sen
10:16
i didn't know that but hell if i care
Kenshin
Kenshin
who is ozzy osbourne
Balarka Sen
Balarka Sen
the green goblin? wait no...
Avantgarde
Avantgarde
the vocalist of black sabbath
one of the first, or pretty much the first metal band
Kenshin
Kenshin
u mean kelly's dad?
Avantgarde
Avantgarde
wait lol
yes.
Kenshin
Kenshin
10:19
oh yeah, i heard of her, didn't know her dad then became famous
so what happened in this interview
Avantgarde
Avantgarde
I didn't know about Kelly
Ozzy Osbourne: "Who The Fuck is Justin Bieber?"
►
Balarka Sen
Balarka Sen
that man gets an instant +1 from me
even though I don't know him
Kenshin
Kenshin
News Alert - Breaking News
►
Avantgarde
Avantgarde
oh man rick again
Kenshin
Kenshin
lol
Ozzy says "Who the f is justin beiber" and means it lol
Avantgarde
Avantgarde
10:22
heh
John Rennie
John Rennie
@BalarkaSen I've seen Ozzy many times over the years and he's really, really good on stage. He has an incredible stage presence and there's always a fantastic atmosphere at his shows.
Though I haven't seen him for a decade now, and ... well ... he's old enough to collect his pension.
Balarka Sen
Balarka Sen
Huh I see
Kenshin
Kenshin
@JohnRennie did you see him eat a bat's head on stage?
does that add to the atmosphere?
Ozzy Osbourne Bites Bats Head Off!
►
John Rennie
John Rennie
No, that was in the US somewhere. And there are conflicting stories about whether that actually happened.
It was allegedly a rubber bat.
Kenshin
Kenshin
oh
Avantgarde
Avantgarde
10:25
@JohnRennie they got done with their farewell tour recently
Balarka Sen
Balarka Sen
well it's still better than MC Ride with the drums and people flying everywhere
John Rennie
John Rennie
@Avantgarde Sabbath did, but that doesn't stop Ozzy doing solo tours.
Avantgarde
Avantgarde
yeah I meant sabbath
John Rennie
John Rennie
Well, I just put in an offer of £325 on that laptop - wish me luck!
Kenshin
Kenshin
yeah it didn't stop John Farnham eithger
Emilio Pisanty
Emilio Pisanty
10:28
0
Q: What are these empty arrows in the migration stats page?

E.P.I'm pretty baffled by these entries in the migration stats page for Physics.SE: What do those migration pathways represent? Shouldn't the UI make it clearer (through some suitable tooltip or other text) what they mean?

discussion migration 10k-tools
user image
Kenshin
Kenshin
you need 10k reputation to see that page
deciphering it must require a secret code only the elite SE users have
@JohnRennie gL
user228700
Ha. Over the past two months, most of my JEE-centric questions have been getting more upvotes and views!
Kenshin
Kenshin
pls show us some
imagine how quiet the chat room will be after JEE
my physics.qandaexchange.com site is gonna die probs too
Slereah
Slereah
10:58
THE GOVT. KNOWS - KNOWER
►
Secret
Secret
11:35
link.springer.com/chapter/10.1007%2F978-1-4419-8077-9_17
Slereah
Slereah
11:47
" Such a notion, termed local covariance was introduced more recently in a programmatic paper [11] by Brunetti, Verch and one of us (K.F.)"
One of the author referred to himself
how gauche
Secret
Secret
0
Q: Will the curvature in space-time prevent an object from moving forever in a friction-less world without air resistance?

Tyler HilbertIn class the teacher said that an object would move forever if you applied a force to it and ignored the affects of friction and air resistance. What I am wondering if that's entirely true. My friend told me that even if there was no friction or air resistance the curvature in space-time would ov...

general-relativity
geodesics
user228700
Absolutely free mental health resources.
user228700
12:02
This seems to be an excellent collection of resources to improve mental health and includes topics such as Building Self Compassion, Improving Self Esteem, and Overcoming Procrastination among many others.
Balarka Sen
Balarka Sen
i procrastinate therefore i exist
Secret
Secret
I don't exist therefore I am
Slereah
Slereah
"Fortunately, there exists a method which is intrinsically local, namely causal perturbation theory."
Is that the coincidence point renormalization
user228700
@BalarkaSen Sheesh, better not read this then!
Balarka Sen
Balarka Sen
Yeah I don't want to stop existing.
Secret
Secret
12:13
I don't exist therefore I exist
Therefore there is no way to remove my existence as I am nonexistent in the first place
Slereah
Slereah
What is a $*$-homomorphism
rejzner.com/files/QFT-Roma.pdf
pretty good paper
Secret
Secret
I suspect $*$ homomorphism are just homomophisms that preserves the structure of the involution $*$ in this algebra, given how the beginning of that paper basically laying down the framework on what a $C^*$ algebra is
0celouvskyopoulo7
0celouvskyopoulo7
@Slereah It commutes with the $^*$ operation.
@Slereah I bought that 50 years of Cauchy problem book.
Slereah
Slereah
Good buy
I hope u like Sobolev spaces
0celouvskyopoulo7
0celouvskyopoulo7
Who doesn't?
Slereah
Slereah
12:26
Me
0celouvskyopoulo7
0celouvskyopoulo7
I don't think you've actually tried to understand them
Slereah
Slereah
Probably not
I barely know what they are
0celouvskyopoulo7
0celouvskyopoulo7
$W^{k,p}(\Omega)$ is just the set of $L^p(\Omega)$ functions whose distributional derivatives can be represented by $L^p$ functions.
Balarka Sen
Balarka Sen
why do i care
Slereah
Slereah
yeah but
what for
also what is the $k$ for
0celouvskyopoulo7
0celouvskyopoulo7
12:30
@Slereah you want derivatives up to order $k$
@BalarkaSen it's the appropriate Banach space for solving differential equations
Balarka Sen
Balarka Sen
@0celo Hm. appropriate in which sense?
Slereah
Slereah
why is it any better than $C^k$
0celouvskyopoulo7
0celouvskyopoulo7
@BalarkaSen In the sense that you can solve the PDE via certain methods (variationally, Lax-Milgram, etc.), then your solution is in $W^{1,2}$ or something.
You then bootstrap to $W^{2,2}$ regularity.
Then by magic, you get $W^{4,2}$, $W^{6,2}$, etc.
The Sobolev theorem says $\cap_k W^{k,2}=C^\infty$.
@Slereah Not a Banach space.
Slereah
Slereah
I guess because some of the functions have unbounded integrals
Balarka Sen
Balarka Sen
@0celouvskyopoulo7 "Huh"
0celouvskyopoulo7
0celouvskyopoulo7
12:35
@BalarkaSen There are many proofs of the Sobolev theorem, none of which are enlightening. Perhaps the best one is via Fourier transform, where you just show that the Fourier integrals for all of the derivatives converge.
But that only works for $W^{k,p}$ on $\Bbb R^n$ or a torus. For worse domains you need god awful stuff like cone conditions and whatnot
$C^1$ boundary usually works
Balarka Sen
Balarka Sen
Ah yeah
PDEs are mysterious. I should know them at some point
0celouvskyopoulo7
0celouvskyopoulo7
You can get Lipschitz too but I've never bothered figuring out how that works. There's a lot of combinatorics behind it.
Mostly you just go to Adams & Fournier and see which Sobolev spaces embed into which $L^p$ or $C^k$ or $C^{k,\alpha}$ spaces and take it on faith.
Slereah
Slereah
is there a necessity to define a fancy integral for the distance function on a manifold, or is it the usual integral since it's just the integral of $d(\gamma) : \Bbb R \to \Bbb R$
0celouvskyopoulo7
0celouvskyopoulo7
@Slereah It's just the inf of lengths of paths, which is just a regular integral.
Slereah
Slereah
Hm
I'm trying to find a reason why Hicks' pseudometric thing is wrong
0celouvskyopoulo7
0celouvskyopoulo7
12:38
@BalarkaSen They are very mysterious
Slereah
Slereah
But I have no idea why
or if it is
0celouvskyopoulo7
0celouvskyopoulo7
@BalarkaSen Linear second order elliptic PDE basically runs on this theorem: en.wikipedia.org/wiki/…
Slereah
Slereah
I suspect it's somewhere in the fact that on non-Hausdorff manifolds, derivatives are probably not equivalent to vector fields
but I'm not sure
16 5
biophysics buoyancy fluid-dynamics general-relativity gravitational-waves navier-stokes optics
Is he related to David Hilbert
Balarka Sen
Balarka Sen
why's Beethoven's 9th symphony stuck in my head. this is NOT helping, brain
Yashas
Yashas
What is the maximum number of reversible paths between two states of a thermodynamic system?
Slereah
Slereah
12:50
"If one does not require continuity there are many more representations"
What's a representation of the Weyl algebra that isn't continuous
John Rennie
John Rennie
@Kaumudi.H I bought that laptop. Oh well :-)
Yashas
Yashas
@AlbertEinstein Hi
0celouvskyopoulo7
0celouvskyopoulo7
@Slereah ask ACM
Slereah
Slereah
@ACuriousMind halp
plz respond
0celouvskyopoulo7
0celouvskyopoulo7
That sounds like something pathological he would know about
Albert Einstein
Albert Einstein
12:59
@yashas, Hello
Slereah
Slereah
$$\omega(A^n) = \int \lambda^n d\mu_{A, \omega}(\lambda)$$
whaaat
I think this is the famed quantum hamburger
You know the moments of the linear functional of the state on the operator and you reconstruct the probability distribution from it
"This is the principle of locality, more precisely expressed by the German word Nahwirkungsprinzip."
AQFT papers love to use that word
"We choose the convention $(+,-,-,-)$"
DROPPED
Yashas
Yashas
13:15
57
Q: Why do metals only glow red, yellow and white and not through the full range of the spectrum?

DieblitzenWhy don't metals glow from red to yellow to green to blue etc.? Why only red, then yellow and then white? Shouldn't all wavelengths be emitted one by one as the temperature of the metal increases? If some metals do glow at with different colours, could you give me examples of such metals and th...

optics visible-light material-science thermal-radiation metals
HNQ :|
The author did not know that the eye perceives white when light of all wavelengths of the visible spectrum enter the eye.
Video Replay: Loops of Fire - Incredible views from the surface of the Sun
Avantgarde
Avantgarde
13:30
empty
Slereah
Slereah
"Embeddings that preserve the metric, the orientation and the causal structure"
What
What more is there to the causal structure than the metric and orientation?
Lozansky
Lozansky
Is this correct $(\mathbf{m}_1\cdot\nabla)(\mathbf{m}_2\cdot\nabla)\dfrac{1}{r}=(m_{1i} \dfrac{ \partial }{\partial x_i})(m_{2j}\dfrac{\partial}{\partial x_j})\dfrac{1}{r} = m_{1i}\dfrac{\partial}{\partial x_i}(m_{2j}\dfrac{\partial}{\partial x_j}\dfrac{1}{r})$
Slereah
Slereah
13:47
"We call a category $C$ strictly monoidal if there exists a bifunctor $\otimes : C \times C \to C$ which is associative and there exists an object $e$ which is a left and right unit for $\otimes$"
Noooo
I just wanted to do QFT
00:00 - 14:0014:00 - 17:0017:00 - 00:00

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