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02:47
@vzn I like how this article is more accurate than typical popsci articles on this topic
03:11
@secret you here?
Is anyone here?
03:47
me
not anymore
vzn
vzn
05:03
@Secret thx for the shades-of-gray thinking! somewhat similarly, preskill recently says we're entering NISQ era, noisy intermediate stage quantum, sounds about right. gizmodo.com/… also has arxiv paper for people allergic to popsci :)
@DanielSank, keep up the good work on quantum systems in thermal and noisy environments, the quantum computing guys may be looking towards the work in order to better their error correction systems
-> (cont. to vzn)
I think quantum computing is not the only thing that characterise this era. There's a lot of other things happening:

Biology: Rapid developments in synthetic biology, and maturation in CRISPR technology as well researches on incoporating microorganisms in structural materials to reinforce their functionalities

Computer science: Artificial intelligence and cryptocurrency

(and one more I forgot)
Technology seemed to be the only thing that is bright, as everything else otherwise mostly go downhill since 2016
Some social scientist predict the western civillisation will enter the destructive phase of a 50 year historical cycle of rise and social collapse by 2020
05:25
in The Biosphere, 1 min ago, by skullpatrol
#BREAKING: China successfully clones world's first macaques from somatic cells by method that made Dolly the sheep 20 years ago (Photos provided by Chinese Academy of Sciences)
---
One one hand, it is really a matter of who gets there first. Will we get into the next breakthrough before we collapse or the final collapse will get us first
On the other hand, I really wish the human race will be wiped out because they have been in general failed to avert those cycles
There are no viable ways to persecute all the karma houdini throughout history, except for a total system wipe
Until we found the first physical infinity, nothing will allow the construction of an attack that can erase a concept permanently
Bakarla: This concept, is what is referred to as the One True Enemy in the anime script
What I detest is not even a human being, but a social phenomenon that have been left unchecked for many eras. Social unrest is just one of its many manifestations
Being a system phenomenon, you will need something akin to calling phone company customer support, and all the possible departments it will refer you to as an excuse all at the same time in one call in order to even make a dent onto this enemy
 
1 hour later…
06:57
28
A: What happened to David John Candlin?

Ron MaimonI googled a little bit a while ago, and found him. I didn't get any insights into the history of this discovery, he didn't respond to my email. The person I contacted in order to reach him was eventually so offended by my rude email questions that he told me to buzz off. I am only posting this be...

07:10
@skullpatrol my goodness he's a big boy. An unexpected side effect of cloning? :-)
07:52
@JohnRennie Indeed :-)
Perhaps it was...
08:13
08:42
09:07
@JohnRennie ...genetically engineered that way?
This raises important bioethical and animal rights issues.
More monkeys, says this impartial observer
@Slereah Perelman?
Zhang?
I dunno
09:32
0
Q: LQP review & voting

Kyle OmanI often come across answers flagged for LQ in the corresponding review queue which don't really fit into the categories of a LQ post - not spam, not better as a comment, not better as a question, etc. Using a broader definition, the post is of low quality; perhaps it's not very clear, or the phys...

@0celo7 There are many trap remixes of Trump
@Slereah This happens to me everyday
Hey @BalarkaSen
09:50
"Yes, but if you only consider positive frequency packets they cannot have compact support on Cauchy surfaces, This is essentially true because they are analytic functions and analytic functions cannot have compact support unless being the zero function."
Malament's theorem is safe again
Hurray
Although I'll need to find out a reason why positive frequency solutions can't have compact support
This sounds like a job for analysis man
@0celo7 halp
10:07
Why are positive frequency solutions to KG analytic
10:52
I think that might be the Paley-Wiener theorem
11:02
When it is stated "consider a $N$ dimensional density matrix" in quantum mechanics, does this dimension refer to the number of eigenstates (or basis states) corresponding to the density matrix?
 
1 hour later…
12:05
"If $f$ is a function in $L^2(\Bbb R^+)$, its Laplace transform is analytic in th upper half space."
Yeah I think it's the Paley Wiener theorem
13:00
@Slereah positive frequency?
@0celo7 Such that the Fourier transform is defined on $(\Bbb R^+)^n$
or something like that
Well, not quite I guess
that the energy spectrum is positive for all solutions
Hm, what would that be for the Fourier transform exactly
$$\psi(x) = \mathcal F^{-1}[\psi(k)] \approx \int d^3k e^{i(p_\mu x^\mu - E)} a(k) $$
So you have $\psi(k) = a(k) e^{-i|k|t}$
Hm
Positive frequency part would just be $\partial_t \psi_k = -i|k|a(k) e^{i|k|t}$ I think
I'm not sure if this is very helpful
But if we're positive energy, that means that $p$ is restricted to the future light cone
Well, I was a bit sloppy, the analyticity domain plays a crucial role. The argument is based on the so-called edge-of-the-wedge theorem. Now I do not remember details. Maybe you can find a discussion in Reed-Simon's book. — Valter Moretti 50 secs ago
Reed again!
Also Wald has it apparently
"We need a sufficiently "nice" class of functions"
13:25
Probably Schwarz
Well it's Wald
No Schwarz space on manifolds
It's test functions
The actual proof is in Streater and Wightman
"PCT, Spin and Statistics, and All That"
"We prove it in the form given by Painlevé in 1888"
it goes back some ways
13:48
Jesus that's a lot of analysis
14:00
The edge of the wedge theorem used takes half a page to even state
@Slereah where is it?
It's in PCT, Spin and Statistics, and All That
it also contains a concise statement of Haag's theorem, which is neat
"Suppose that $\phi_1(x)$ is a free hermitian scalar field of mass $m > 0$, and $\phi_2$ is a local field covariant under the inhomogeneous $SL(2, C)$. Suppose further that the fields $\phi_1, \dot \phi_1, \phi_2, \dot \phi_2$ satisfy the hypothesis of theorem 4.14. Then $\phi_2$ is a free field of mass $m$."
4.14 is basically that $\phi_1$ and $\phi_2$ belong in two Hilbert space and are related by a unitary transformation.
@ACuriousMind had some spinach
good for him
he will grow strong
(toot toot)
Although I'm guessing making a Popeye joke to @0celo7 won't fly since he knows nothing before 2000
I might as well make a Canterbury Tales joke
I read Canterbury Tales
Also I know Popeye, though I've never seen it (why would I?)
14:14
it's a classic cartoon
@Slereah I've decided to take GR out of the thesis
it would be too ambitious otherwise
Possible footage of @ACuriousMind eating spinach
Was it even in?
I thought it was just the PMT on Riemannian manifolds
I said I had spinach
@Slereah I took the PMT out
@0celo7 Careful with ambiguous phrasing then
Oh
it's just the Yamabe problem now
14:18
What is it about now
it was always the Yamabe problem but I wanted to do the PMT in dimensions $\le 7$
probably good yeah
it would have at least doubled the thing
a full proof of the PMT would be a good project for later
including the folklore parts like capping ends and smoothing singularities
it seems much more manageable now
I am so bad at analysis
especially when they bring up complex analysis
14:29
Is it the famous conway
ah no
Famout at my school
I'm thinking of John H. Conway
He used to be department head here
I have this one and his functional analysis book
(One of the greatest books ever written)
JB is quite famous too
not as famous as JH tho
Famous for his books, I think
I'm not sure what he actually did
14:32
yeah
I don't know much math.OA stuff
I go to the seminar but it's like wot
I usually go with the geometry guys and we just look at each other halfway through and read whatever books/papers we brought
Pretty easy to get lost
operator algebras
JB worked in the intersection of operator algebras and complex analysis
there's a correspondence between von Neumann algebras and Hibert spaces of holomorphic functions in the disk
reproducing kernel Hilbert spaces and all that
I don't really know what the other conway really did
He is mostly known for weird stuff
group theory
14:40
Game of life, surreal numbers and the see and say sequence
I need to read this French paper
where did I put it
France, possibly
it seems to be gone
crap
what paper was it
oh no there it is
"Remarque sur le probleme de Yamabe"
14:44
I should sort my papers more
but there are so many by now
Probably close to 10.000
Some I don't think I will ever read
I need to decide how many proofs of the final step of the Yamabe problem I really want
it would be impressive if I translated the French proof
need help?
@Slereah maybe, I'm gonna go print this and start working on it
Thankfully it's pretty short
it gives a very nice formula for the ADM mass which is cool
Is the exponential map of a random manifold the exponential map of the diff. group of the manifold?
with the Lie bracket as the algebra
no
how on Earth does one TeX that
14:51
:D
lots of underset
I guess
7 pages
unless there's a massive calculation they're hiding, this is wonderful
sadly it's hard to skim
I wonder when French people stopped writing papers in French
I think the 70's-80's
this is a 91 paper
In French?
yes
15:07
Weird
damn, temps go from freezing to chilly today
gotta dress in a modular fashion
@Slereah also they don't seem to write Proof anywhere
it kind of just all flows together
Will you dress in a $C^\infty$ module
no, probably an $RG$ module
I like how people say things are obvious in 1984 but the proof doesn't appear until 1996
The hunch that it is correct was obvious, probably
Should that $d_\mu$ be a $\partial_\mu$? — 0celo7 Feb 24 '15 at 4:25
I still agree with this
$d_\mu$ is nonstandard
15:20
Also is it actually a total derivative?
yes
Oh yeah right
That's Important for the constraint thing
otherwise you wouldn't get second order field equations
yeah, since most of the time the action doesn't depend explicitely on $x$
I think I'm going with the French proof
It doesn't involve the horrible $\varepsilon$ argument
15:31
what would be a good way to differentiate partial and total derivatives, tho, for multiple coordinates
@Slereah the math people do it with parentheses
Differentiating before or after plugging in arguments
I think in physics it's kind of implied by writing $\mathcal L (\phi(x))$
Then you can just pretend it's a composition of functions
And then the partial derivative acts like a total derivative
15:46
The two different notions of magnetic moment is confusing
Where is @JohnRennie when you need him?
@BalarkaSen Currently lurking in the SF Stack Exchange trying to answer a story ID question.
nerd
Do you have any insightful lights to shed on the various notions of magnetic moment and the magnetic pole strength?
Lightful insights will also suffice
Are there different notions of magnetic moment? Isn't it just related to the torque in an external magnetic field?
Well it seems you define the quantity for magnetic dipoles (which are just current carrying loops in your field) and actual magnetic materials
The latter thing comes from the torque
$\tau = p_m \times B$
15:57
I'm having trouble seeing a general theory of magnetic materials. The textbooks writes a bunch of definitions in a scattered way
But I need to scurry off in a few minutes. If you want to write something/refer to something I'd have a look once I'm back
I am notorious for my deep love of electrodynamics. I'm pleased you are coming to see my point of view.
Why do the French use X for manifolds when it should be V
I dunno but $X$ is common for topological spaces
I've seen $V$ used tho
“Le meme”
Fuck the French are Years ahead of us
(it means the same)
16:17
Can you form a Hilbert space with any field
Or does it need to be complete wrt some norm
@Slereah you need to be more precise with your question - the standard definition of "Hilbert space" explicitly demands a real or complex vector space
must the definition of a Hilbert space consist of an inner product?
If you’re from 1960 it can be defined as a Banach space satisfying the parallelogram law
16:33
@0celo7 sure, and then the definition of Banach space, or rather normed vector space, includes the "real or complex" stipulation
I was answering @CaptainBohemian
Ah, but then you should mention that the parallelogram law is equivalent to there being an inner product ;)
I figured that was obvious because I said it’s another definition
I've seen Hilbert spaces with other fields
Was it all lies
The French paper has a mistake/weird thing in it
Somehow they construct the Green’s function in two lines but in their book it takes a chapter
I’m missing something
16:40
@Slereah the author probably redefined the notion of Hilbert space to include their versions.
I'm not saying there aren't "good" ways to extend the concept, just that the question makes little sense using the standard definition
Presumably it works for any complete field.
Who knows what generalizes, however.
Is there a p-adic Hilbert space
Could b
Do you want to submit to the Journal of p-adic quantum physics? :P
Never seen a manifold called $V$ I don't think, always $X$!
You haven’t read enough then
16:51
@ACuriousMind actually I think it's been done before
Yvonne does V I think
There has been a lot of variants of QM done really
Usually to little success
17:08
> I would like some reassurance about some minor technical aspect of my workings, and some validation of my status as a competent student of physics.
I hope I didn't just overstep some invisible line I oughtn't have done
17:19
"This observation initiated the study of p-adic string theory."
This might be the worst sentence
Don't you hate it when you spend an hour going what's wrong to find you missed out an asterisk...
Anonymous
@CooperCape Happens to me almost everyday :P
Just like bro I could've done with that extra hour...
Found out I lost 6 marks in my inorganic chemistry for thinking that the Mr of Na is 11 not 23...
Anonymous
Ah, that sucks. I'm waiting for the day I don't have to write any more exams...
Ugh I still have too many of those left :p
17:39
@JohnRennie lol
is electrodynamics real
or is it just a scam like QM
@0celo7 V is Russian notation for manifolds
Anonymous
@BalarkaSen Could you tell me what you're looking for?
Anonymous
Are you confused with those H,B stuff?
scroll up...
17:41
Manifold is apparently Многообразие
Meogoodraie?
I dunno
Apparently it's a calque on the french word for manifold
Hence probably why they use $V$
Anonymous
2 hours ago, by Balarka Sen
Do you have any insightful lights to shed on the various notions of magnetic moment and the magnetic pole strength?
Anonymous
2 hours ago, by Balarka Sen
I'm having trouble seeing a general theory of magnetic materials. The textbooks writes a bunch of definitions in a scattered way
Anonymous
Which definition(s) are you having trouble with?
17:44
definitions are ok. the general picture is not
Anonymous
Okay, but I still haven't understood your question, from the transcript. I could help if you write it more specifically. I can explain you the theory of magnetic materials in brief if you wish.
Anonymous
Also there are not multiple notions of magnetic moment and magnetic pole strength...
magnetic moment of a magnetic dipole and a magnetic material in your field seems to be very different notions to me
Anonymous
@BalarkaSen Okay, I understand your confusion I think. Do you know about "magnetic domains" in magnetic materials?
Ah no. Want to explain?
Anonymous
17:51
I guess Wiki can do it better than me: en.wikipedia.org/wiki/Magnetic_domain
Anonymous
;)
Anonymous
Magnetic domains are basically regions in which magnetic moments of atoms are aligned in the same direction
Anonymous
The total magnetic moment of a material is basically the vector summation of those
ewww domains
@Blue Ah...
17:55
@BalarkaSen lies
@0celo7 See Eliahghjhhkhbberg Mishflkgkkjlflev
mb they stole it from the french
I don't believe in the French
3
Anonymous
@BalarkaSen You know multipole expansions, right?
@Blue Nope
@0celo7 You say Voltaire, I say Pushkin, you say Sartre, I scream Dostoyevsky, you say French revolution, I retort, Bolshevism!!! you say Paris, I say Stalingrad, you say guillotine I say: GULAAAAG
18:02
Cyka blyat
Anonymous
@BalarkaSen Well, magnetic moment produces the first term in multipole expansion of a magnetic field (that's the more accurate definition). Similar to first order approximations...And that normally dies down as $1/r^3$
@Blue That's kind of cool. So what is the multipole expansion (I understand it's a power series expansion of the magnetic field?)
Anonymous
Yeah, it's like a power series. Look up spherical harmonics and multipole expansions on Wiki. It's interesting
Thanks, I shall have a look
18:38
@0celo7 joji dropped a vaportrap track again lmao
19:37
Oh my god
Equation 2
Found it after days
!!!
It's a reformulation of the linearization of the EH action, not the full action!!! 2 days wasted trying to link the full one to this!
Who said they spent an hour missing a comma, imagine days trying to link n dimensional non-linear einstein-hilbert actions to linear ones in vielbein form!!!
Bamboozled again
Oh my god I thought that would never work out, no wonder
Linearized teleparallel gravity apparently, my god
is that the linearized torsion
19:52
I think so
vzn
vzn
@EmilioPisanty strange, seems to be broken. the outside links ref nature site in general but not the (QM physics) article in particular.
20:44
@Slereah damn, I have a love/hate relationship with the French
I think there's a very stupid mistake in this paper
shame on you!
Send them a sternly worded letter
@Slereah they seem to have corrected it for the book
that is good
21:06
@Slereah the error seems to be showing up a few times :/
This time it’s more serious, i think
does it make the proof invalid
I dunno. French geometry usually takes a week to figure out
They’re very...concise
concise in the notation or do you mean they just say 'the proof is obvious from there'
21:27
il est obviouse
Bourbaki's Manifolds book used a French X for manifolds iirc
'The notion of Fivebrane structure is the next higher analog of that of spin structure and string structure.'
What's special about 5
22:02
@vzn altmetric is hopelessly broken
It's just not important enough yet for people to really start scrutinising it in earnest
See also
6
Q: What's the deal with Altmetric? How reliable is its scraping, and how often does it happen?

E.P.Altmetric is a service that attempts to track the online impact of scholarly articles, which it does by keeping score of mentions on Wikipedia, Facebook, Twitter, blogs, and the like and then using questionable cutting-edge statistical methods for producing one shiny number for bean-counting admi...

That's from a year ago
The d examples it links to are still broken
22:32
5
A: Why is Standard Model + Loop Quantum Gravity usually not listed as a theory of everything

Urs SchreiberOne can pinpoint the technical error in LQG explicitly: To recall, the starting point of LQG is to encode the Riemannian metric in terms of the parallel transport of the affine connection that it induces. This parallel transport is an assignment to each smooth curve in the manifold between point...

Urs (ncat guy) uses functors and holonomy to argue against lqg
Soft cover version is a pretty normal price
Maybe I should get it
23:07
@EmilioPisanty People need to hear that kind of advice.

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