« first day (2648 days earlier)      last day (2577 days later) » 
01:00 - 22:0022:00 - 00:00

vzn
vzn
01:39
remember when eg 0ce was mad about SJWs? this reminded me... "snowflake bingo" lol dailymail.co.uk/news/article-5346693/…
 
3 hours later…
Secret
Secret
04:36
ams.org/journals/notices/201802/rnoti-p167.pdf
 
2 hours later…
skullpatrol
skullpatrol
06:39
@bolbteppa thanks for sharing :-)
 
2 hours later…
Tanuj
Tanuj
08:35
Hello everyone! Could someone please help me get over a question related to fluids? (viscosity). I've really racked my brain out but I'm stuck real bad.
@JohnRennie could you have a look at it please?
John Rennie
John Rennie
@Tanuj what is the question?
Mithrandir24601
Mithrandir24601
@vzn As per usual, the daily mail has cut out all the context, then warped things until it's unrecognisable (in at least some of that article). There are a couple of things that the NUS (National Union of Students) have done at recent conferences. Oddly enough, it's lost a lot of credibility in said years, so things that the NUS have done is not necessarily representative of the wider student population.
About the deadlines one: The UK is finally waking up to the fact the mental health is actually a thing, never mind that most uni degrees are getting harder due to increased competition. Also, a number of these are about specific outlying people, not large groups.
So, while yes, there are people who are "permanently offended and moaning endlessly", in my experience, calling it "a generation" is definitely much overkill and is just demeaning to the vast majority of people under the age of ~40 (i.e. 'millennials', which is an oft misused term)
(although personally, yeah, if I wore a sombrero and was told I was being racist because of it, I'd be extremely tempted to say things like "get a life")
John Rennie
John Rennie
The Daily Mail?
Mithrandir24601
Mithrandir24601
@JohnRennie yep...
John Rennie
John Rennie
08:50
Really? Someone is taking the Daily Mail seriously?
Mithrandir24601
Mithrandir24601
@JohnRennie I really hope not, but @vzn linked the article above, so I wouldn't make that assumption so quickly :P
skullpatrol
skullpatrol
do you guys think the bourbaki had any influence on how maths was taught in the UK?
John Rennie
John Rennie
@Mithrandir24601 Ah yes, vzn is something of a Daily Mail fan. What that says about his grasp of reality I'll leave it for others to decide. I didn't see his comment since I have him on ignore - something that significantly improved the chat experience.
@skullpatrol I'm not sure we have any UK mathematicians hereabouts to comment. You're probably better off asking in the Math chat.
skullpatrol
skullpatrol
well, the math used in high school physics
Mithrandir24601
Mithrandir24601
@skullpatrol I've heard of the existence of something called Bourbaki, but I don't know what they have or haven't done, so it's still not a trivial question :P
John Rennie
John Rennie
08:57
As far as pre-university maths goes I don't think Bourbaki has had any influence, but then you wouldn't expect it to. Pre-university maths is a pale shadow of the maths you study at university.
Mithrandir24601
Mithrandir24601
@Blue I feel like I should strongly disagree with this (something along the lines of martial arts isn't just about learning to fight?) but you make such a brilliantly clear and fantastic point, that I feel obliged to give you a star instead
Anonymous
@Mithrandir24601 Hehe. At least someone understands me :P
Dawood ibn Kareem
Dawood ibn Kareem
@Mithrandir24601 Is it racist to wear some other group's national costume?
Anonymous
BTW I found a really wonderful video yesterday:
Anonymous
Quantum Entanglement & Spooky Action at a Distance
►
Anonymous
09:09
Strange that I didn't find any good stack exchange answer which explains it well (as to why faster than light communication isn't possible using entanglement)
Anonymous
And the books are too convoluted to make sense. @BalarkaSen was asking about this a few months back
Cows
Cows
playing with posgres
Mithrandir24601
Mithrandir24601
09:41
@DawoodibnKareem It's just a hat... Generally, it's considered a good thing when a country's culture spreads to another
Dawood ibn Kareem
Dawood ibn Kareem
I agree with you entirely. I am wondering why anyone would call a sombrero-wearer racist.
Unless they happened to be racist in addition to wearing a sombrero, of course.
Round and round the rugged rocks, the sombrero-wearing racist ran.
Mithrandir24601
Mithrandir24601
10:26
@DawoodibnKareem So am I :P
Mithrandir24601
Mithrandir24601
10:43
@Blue There's a few different answer to this: Some will say that it's what the maths says; others that you need to send classical information in order to get the right measurement basis as the density matrix is in a mixed state until that classical info is received. This is the closest 'commonly used' argument to what I'd say that the best answer(s) is/are. It's good most of the time but runs into issues when you start considering the same problem in the context of boosted frames
Anonymous
@Mithrandir24601 Sounds interesting. I don't know how the details of the issues which arise as a result of Lorentz boost of coordinate frames. Do you have any references/articles which discusses this? (I'm a bit rusty in SR....gotta revise....)
Mithrandir24601
Mithrandir24601
11:03
@Blue It's along the lines of section IV of this - it's not saying QM is inconsistent (quite the opposite), but it does lead to some questions about when wavefunction collapse actually occurs and could the same density matrix look different to different observers, at which point the best thing to do is to delve into reference frames, where things get very interesting
Cows
Cows
11:24
Off to bed. Will continue coding in the morning. I have to master 15 tools. 7 automation strategies and some cs theory before monday. Also need to be fluent in architecture security and load balancing. Good times !!
 
2 hours later…
2physics
2physics
13:08
Hi, any body can introduce some sources(books, papers, links or whatever) to know more about what discussed in this question? Thanks!
Anonymous
13:39
@0celo7 You had a course on fluid mechanics, right? I need some help regarding the math related to coalescing of liquid drops
0celo7
0celo7
13:54
@Blue that’s not standard material, but ok
What’s the issue?
Yashas
Yashas
Why is that the energies of atomic orbitals of lower atomic number are higher (in the same period)?
For example, the 2p orbitals of carbon is higher than that of oxygen.
(every textbook shows 2p orbitals to have higher energy than oxygen in the CO molecular orbital diagram)
bolbteppa
bolbteppa
14:14
@Kolmin what is going on in proposition 1, looks absolutely crazy e.g. using Hahn-Banach to prove it yet it's probably just saying the properties of a norm, or probably a semi-norm, can be re-expressed in terms of convexity?
Tanuj
Tanuj
@JohnRennie thanks for replying back. Are you available right now?
0celo7
0celo7
@bolbteppa who is kolmin and why are you talking about Functional Analysis without me
John Rennie
John Rennie
@Tanuj hi, yes I'm around. What did you want to know?
Tanuj
Tanuj
@JohnRennie I have posted my doubt in on uthe other room. The problem solving stratergies.
bolbteppa
bolbteppa
6
Q: On Bourbaki's "Integration" - Why/What/How to read it

KolminI have a question concerning the Bourbaki's book on integration. Whenever I find them referenced (in answers on this site as well), it looks like they aged more than volumes of the same series on other topics. Also, it looks like they were criticised from the outset (e.g. see Halmos' comment fro...

integration measure-theory math-history
Who knew HB could be used to prove Holder and Minkowski
0celo7
0celo7
14:34
@bolbteppa what?
Why would you need HB for that
Are they doing integration with values in a TVS or something?
bolbteppa
bolbteppa
No it's on $\mathbb{R}^n$,
"Ch. I: Very general Holder and Minkowski inequalities, applicable to positive functions defined on a set, on which there is no topology or `integral' in sight (Ch.I, Props. 2,3).

Prop.1 uses the Hahn-Banach theorem (`geometric form') in $\mathbb{R}^n$; there is no free lunch.

The payoff : it expedites the (simultaneous) construction of the function spaces $L^p$, ($1 \leq p <+ \infty$) and the integral on $L^1$, even for vector-valued functions."
p. 6 https://www.ma.utexas.edu/mp_arc/c/08/08-234.pdf
Secret
Secret
@Mithrandir24601 I think that agrees with the various experiments such as entanglement swapping in time and the numerous spacelike entanglement experiments that tests bell inequality.
bolbteppa
bolbteppa
Ahh, they use HB to prove something about (what will become) an outer measure as their very first result and use this to prove Holder and Minkowski, crazy
Secret
Secret
I am now inclined to believe that what actually happens is that in the frame of one of the subsystems after a measurement is being made, what happens in the other subsystem is a statistical mixture until the classical information carrying the outcome of the measurement of the other subsystems arrived to establish which of the correlated observables that the system have obtained
12
A: "FTL" Communication with Quantum Entanglement?

CR DrostYou have a wrong understanding of quantum entanglement. What is entanglement? Quantum entanglement emerges naturally from the "only obvious way to do things" at the wavefunction level (distribute a wavefunction over all possibilities of two subsystems), and describes the fact that the general s...

for example here, in the answer given, the interference pattern of the other subsystem will look like there is no interference until the information that carry the correlation arrived that allow us to resolve the statistical mixture and hence recover the two interference patterns
Secret
Secret
14:56
wow, after watching that video linked by blue, I now started to understand how restrictive local hidden variables are:
user image
Anonymous
user image
Anonymous
@0celo7
Anonymous
I don't understand which distance they are considering as radius of meniscus
Secret
Secret
Having particles that conspire to measure the same or opposite depending on how the detectors are arranged is simply way too many correlations that should not be there
Anonymous
Shouldn't the radius of meniscus be the radius of upward facing arc of which the meniscus is a part of?
Anonymous
14:58
Rather than the height which they have shown? (Got it from here-Page 26 and here - Page 3)
Mithrandir24601
Mithrandir24601
@Secret I haven't read through all that + links, but from a glance, it looks like what I know as 'time-bin encoding', while I'm looking at the questions that arise from asking things like "who measured first?" and "if you perform a boost (or rotation, or similar) on a frame, what happens to the density matrix that arises from measuring a single particle of an entangled pair", which is based more around the effects of reference frames, as opposed to entanglement
Anonymous
user image
Anonymous
I would expect $r_m$ to be something like this
Mithrandir24601
Mithrandir24601
@Secret This sounds right, apart from fiddly details about reference frames, which is (more or less) related to what that classical information is
0celo7
0celo7
@Blue rm is on the picture
It seems to be the height from the plate to the side of the meniscus
Anonymous
15:05
@0celo7 Yeah, but that doesn't even look like a "radius"!
0celo7
0celo7
I agree
Anonymous
Phew phew
0celo7
0celo7
What you drew is more reasonable, namely the inverse of the curvature
Aka radius of curvature
But that’s not what they’re doing...so...
Keep reading and see if what they do makes sense in the end
Anonymous
Yeah. They should have just called it height or something.
Secret
Secret
hmm...
Now compare the above with the following qualitative "watered down" analogy

We prepared two marbles A and B, both colorless. Each carry an instruction of probability which reads as:

When touched, turn into (R)ed rA amount of the time or (Y)ellow yA amount of the time

similarly for B. Should we decide to touch either of them, they will change color, and we found there is no correlation between the colors R and Y.

We brought the marbles close together, leave that for some known amount of time t. The two marbles are still colorless.
Your marble experiment does not violate Bell's Theorem (or any other theorem of classical probability) and is therefore quite entirely irrelevant to the issue here. The wave function does not count as a hidden variable because it cannot *determinstically predict the outcomes of all measurements. In your marble experiment, we can easily explain the result by invoking some determinstic (though mysterious) force. — WillO Apr 29 '17 at 15:47
Anonymous
15:07
I have started to sympathize with you @0celo7. We share the hate for physicists :P
Secret
Secret
I think I might have some idea on where my analogy went wrong:
> Repeat Steps 1-3 many times and we found that R and Y are correlated in a way that agrees with the resulting probability of what happens when objects with some given instruction of probability (inferred during the preparation of the marbles) is being place close together for time t.
0celo7
0celo7
@Blue all reasonable people do
Secret
Secret
I specified some fixed probability distribution on the marbles, thus introduced some determinism without knowing
Mithrandir24601
Mithrandir24601
@Blue NOOOOOOOOOOOOO!!! COME BACK!!!
Anonymous
@Mithrandir24601 Lol. I still like physics
Mithrandir24601
Mithrandir24601
15:09
@0celo7 OY! :P
Anonymous
@Yashas Ask the Chem QM guys. They can show you all the calculations. Orbitals for atoms are gross generalizations anyway
Secret
Secret
With the help of the video, I now understand why I cannot simply treat the outcome of entanglement particles as a sample space of correlated outcomes which is then randomly draw from it when a measurement is performed, because then I will have implicitly specified a scheme on how the particles will behave when being measured while the real case is that the particle have no such plans hence no dependence on how the detectors are arranged
Anonymous
MOT is a better version. But even that is an approximation (a very reasonable one though)
Mithrandir24601
Mithrandir24601
@Secret you might want to check out Popescu-Rohrlich boxes
Secret
Secret
2
Q: Difference between PR correlations and entanglement correlations?

Secret(As pointed out by helpful users, one of the bolded claims is interpretation dependent. Therefore, unless otherwise specified, Copenhagen interpretation is used throughout) Recall that for classical correlations, the observables are already determined even before a measurement, and thus knowing ...

quantum-mechanics non-locality
I have an unanswered question on this, I still yet to figure out how they work since I am so poor at dealing with inequalities (my brain go BSOD if I see 3 or more inequalities appeared in one line)
Sid
Sid
15:17
Hey guys!
bolbteppa
bolbteppa
Of course they begin from topological vector spaces which are left modules over a valued division ring because of course you want to make sure your theorems apply to convex spaces with quaternion coefficients
Secret
Secret
user image
This is indeed a wonderful video: THAT is entanglement in a nutshell
I think quantum textbooks should stop using the bell states to illustrate entanglement, and should use an entangled state where the observables are not opposite pairs
because once you see e.g. the above and e.g. when you have the following entangled state:
$$\frac 12 (|00\rangle + |01\rangle + |10\rangle - |11\rangle)$$
and then realise from the density matrices and reduced density matrix calculations, that whenever you get a 1 or 0 half of the time in subsystem A, you still get a 50:50 mixture of the interference pattern $\frac 1\sqrt{2} (|0\rangle \pm |1\rangle)$ until you have the classical information to resolve it, then the conclusion that there are no local hidden variables should be apparent
$\frac {1}{\sqrt{2}} (|0\rangle \pm |1\rangle)$
Anonymous
@Secret Nods! It was very confusing for me initially to grasp the general concept using the commonly used Bell states (which have the rotational invariance property). Discussing it in a more general setting would be much better.
Physics Meta
Physics Meta
1
Q: Is PSE the place to ask for clarification on scientific talks?

Carvo LocoI've been watching a talk about physics by mathematician Marcus du Sautoy and I was left with some questions that were not addressed in the talk's Q&A session. Is it appropriate to ask those questions at Physics Stack Exchange? And, if so, is it advisable to bundle them into a single question wit...

support
Anonymous
By the way, Vazirani's videos also helped me quite a bit.
Anonymous
15:26
He doesn't shove the math under the rug and discusses most of the proofs
Anonymous
(It's available on YouTube)
0celo7
0celo7
@Mithrandir24601 ur an engineer
Mithrandir24601
Mithrandir24601
@0celo7 Well... Not really, but why not? :P
Secret
Secret
Attempt on quantum mechanics in pictures:
Anonymous
"Quantum engineer" sort of sounds really cool though. You should be content with that title XD (Added advantage that most people won't even understand what you actually do)
Sid
Sid
15:35
Who is a Quantum engineer here?
Anonymous
Mithrandir and Daniel Sank
Anonymous
DS is a "Quantum Electronics Engineer" :P
Sid
Sid
So cool. What do you do again? :P
Mithrandir24601
Mithrandir24601
@Blue hence the "why not?" :) To be fair I am involved with simulations on a quantum (photonic) chip
(As opposed to DS, who's involved in the process of actually making quantum (superconducting) chips)
Future Historian
Future Historian
Hmmmmmmmmmmm.
Mithrandir24601
Mithrandir24601
15:38
(and waay past the point of being a student)
Future Historian
Future Historian
So....trying to find where in the Milky Way these coordinates are:
69.750185 degrees galactic longitude, 14.984267 degrees galactic latitude.
0celo7
0celo7
I'm an inequality specialist
@Blue are you including MMA in your starred quote?
Anonymous
@0celo7 Probably not. That falls in the sports category
Anonymous
Y u ask
Secret
Secret
user image
and so it boils down to:
We could only ever experimentally measure the statistics of the projection of a quantum state, and never the whole thing at once!
(I need to figure out how to include the uncertainty principle, since noncommutativity is something that is not easily illustrated on a diagram)
Actually, I need to revise the diagram later, as at its current state, it seemed to suggest the orientation of the spins in the entangled states are fixed, while in reality, we can say nothing about its orientation (wrt some reference orientation) until after we measure them via quantum tomography
Mithrandir24601
Mithrandir24601
16:02
@Blue This just keeps getting better :D
Secret
Secret
So, given some entangled state that is being prepared by some procedure but the details are not known, we can determine the correlation involved by first finding the orientation of one of the detectors in the subsystem such that you get a certain value of an observable 100% of the time. Then in such a state, the detectors will be positioned in a way such that at least one is aligned closest to one of the any eigenstate of the joint observable of the entangled state. If
our entangled state has only 2 subsystem then ensuring one subsystem to always e.g. measure spin up for a given detector position, then the statistical information from the other subsystem will allow us to obtain information of the full entangled state.
Above claim need to be checked with the maths using a generic entangled state later...
Mithrandir24601
Mithrandir24601
@0celo7 Put it this way: learning to fight fairly 1-on-1 isn't 'real world'. Learning something like BJJ, which (by the sounds of things) seems to be fantastic in the ring still isn't 'real world' (i.e. you get someone on the ground and you'd get stabbed pretty quickly by others if you haven't already). For the record, learning historical stuff isn't real world either. 'Real world' is going on the streets, getting stabbed and waking up in hospital. If you're lucky
Anonymous
@Mithrandir24601 :) Pretty much sums up what I wanted to say
Mithrandir24601
Mithrandir24601
In other words, I really wouldn't want to learn 'real world' 'martial arts' because I'd probably die. Very quickly. Having said that, skills that virtually any martial art teaches you would be useful in some way in the 'real world' and has other, more relevant uses, such as keeping calm and controlled under pressure, improved reflexes and is very good exercise
@Blue exactly :)
(oh, also - it's extremely fun. That's the most important bit :D )
Secret
Secret
but the main idea is, every observable of a quantum state has its associated unique eigenstate due to the hermitian property. Therefore, for a bipartite entangled state, the eigenstate will be a tensor product of two state vectors, so if we align one of the detectors such that one of the subsystem is effectively aligned with one of the elements of the tensor product, then the outcome of the other detector will give a statistical distribution of part of the joint observable, thus allowing us to
establish the details of the original state.
Of course, the above will fail if the eigenstate of the joint observable is also an entangled state
ok, just checked, there are joint observables where the eigenstate are entangled
So...
My recipe of doing quantum tomography on an unidentified n-partite entangled state is as follows (assuming there are a huge number of replicates prepared):
1. n determines the number of detectors you need to do the tomography
2. Now you need to choose a bunch of detectors to measure the 1st subsystem. Test each detector until you find one detector with a certain setting such that the resulting observable is obtained 100%. After this stop and move to the next step
3. Repeat step 2 on the remaining subsystems one at a time until all n subsystems are dealt with
4. You now found a joint observable such that the entangled state is in an eigenstate. Use all the statistics you obtained to reconstruct the entangled state
I am pretty sure there are more efficient ways that does not require crawling through the space of all observables (hence type of detectors being used)
Quantum tomography
Quantum tomography or quantum state tomography is the process of reconstructing the quantum state (density matrix) for a source of quantum systems by measurements on the systems coming from the source. The source may be any device or system which prepares quantum states either consistently into quantum pure states or otherwise into general mixed states. To be able to uniquely identify the state, the measurements must be tomographically complete. That is, the measured operators must form an operator basis on the Hilbert space of the system, providing all the information about the state. Such a set...
hmm... so using detectors that only give binary outputs, or search for the density matrices that most closely recover the experimental results
a lot more efficient that what I suggested above, especially there is no way to determine whether you have 100% probability or just some number very close to it experimentally
Secret
Secret
16:30
Philosophy: Given the huge number of types of observables we can use to represent a quantum state, from momentum, to spin to positions to path information etc., I think the physical nature of a quantum state/wavefunction is information
more precisely, a list of statistics of some physical properties that evolves deterministically with time
sbp
sbp
hey how can I compute the generalised force for a given potential?
$-\frac {\del V}{\del q_i}$ ?
Anonymous
@sbp Yes (farside.ph.utexas.edu/teaching/336k/Newtonhtml/node76.html)
sbp
sbp
@Blue
thanks
Secret
Secret
user image
ok, computed the PR boxes probabilities, now to compare them with entanglement probabilities
sbp
sbp
So for say $V = \frac{1 + \dot q}{q^2}$, then $Q_j = 2 \frac{1 + \dot q}{q^3}$ ?
CooperCape
CooperCape
16:43
please tell me I'm not going mad and that $\ln|\cos x|=-\ln|\sec x|$
Anonymous
@CooperCape Looks fine as long as $\sec(x)$ is defined
CooperCape
CooperCape
I mean it's just an integration questino
Anonymous
@CooperCape Yeah, that formula is fine
CooperCape
CooperCape
just that answers give it as -ln|sec x| and I spent a while thinking I had it wrong...
which is always annoyin
Anonymous
@sbp Does not make much sense. You'd want to take the gradient. $q$ is not one-dimensional (normally)
Anonymous
16:47
And if it is one-dimensional you should not write it as $Q_j$
Anonymous
@CooperCape Hehehe. Integrals are tough nuts :P Also don't forget the constant!
CooperCape
CooperCape
I ALWAYS forget the damn constant
except for the ones with limits... cause... yano
Anonymous
Yeah, that's one problem about indefinite integrals. Equivalent forms may look very different
Sid
Sid
@CooperCape you're in trouble pal.
CooperCape
CooperCape
My teacher just looks at my work and tells me I got 0
cause no C
But currently doing easy af by parts cause they all like $\int x\sin x dx$
Sid
Sid
16:49
@CooperCape your teacher is crazy.
Secret
Secret
Ok, I think I am starting to get it:
CooperCape
CooperCape
Ehh a tad
Secret
Secret
user image
Classical correlations: Correlations are already established as a preexisting observable
Entanglement correlations: The statistics of the spectrum of observables are correlated independent of detector configurations
CooperCape
CooperCape
So all the question 1's are similar to x sin x, and all the question 2's are similar to x^2 sin x, I'm not holding out much hope for the question 3's...
Secret
Secret
PR correlations: The statistics of the outcomes are correlated to the joint probability distributions of the two spacelike separated parties
Sid
Sid
16:53
@CooperCape I am guessing, x sin x, then, x cos x and so on
Secret
Secret
Since the statistics of the outcomes are correlated to the joint probability distributions of the inputs, and not independent of it, PR boxes has a much higher correlation than entangled states
CooperCape
CooperCape
@Sid Well sometimes it goes crazy and throws in an x sec x tan x
Secret
Secret
17:05
Moreover, the PR boxes are no signalling. While from the above 4x4 table it seems the probability distribution itself will change depending on the inputs, Alice and Bob cannot detect the difference since all they can see are just 0 and 1 pop out 1/2 at a time. Without actually coming together to see the joint outcomes, they will not be able to figure out whether they are getting 50:50 00 and 11 or 50:50 01 and 10
Anonymous
@Yashas I forgot to mention. This is a good book which discusses the derivation of orbital theories
Secret
Secret
and so... an entangled PR box will be something where the PR box's configuration form an entangled state:
Secret
Secret
17:21
PR entangled box:
$$\frac{1}{\sqrt{2}}\left( \left|\boxed{\begin{matrix}p & 0 & 0 & 1- p\\ p & 0 & 0 & 1- p \\ 0 & p & 1-p & 0 \\ 0 & p & 1-p & 0\end{matrix}}\boxed{\begin{matrix}p & 0 & 0 & 1- p\\ p & 0 & 0 & 1- p \\ 0 & p & 1-p & 0 \\ 0 & p & 1-p & 0\end{matrix}}\right \rangle + \left|\boxed{\begin{matrix}p & 0 & 0 & 1- p\\ p & 0 & 0 & 1- p \\ 0 & p & 1-p & 0 \\ 0 & p & 1-p & 0\end{matrix}}\boxed{\begin{matrix}p & 1-p & 0 & 0\\ p & 1-p & 0 & 0 \\ 0 & p & 0 & 1-p \\ 0 & p & 1-p & 0\end{matrix}}\right \rangle\right)$$
where columns represents the inputs 00,01,10,11 of Alice and Bob, and rows represents the outputs 00,01,10,11 of the PR boxes. The joint probability distributions were given as entries
So PR boxes are very powerful computational tools since its output statistics depends on inputs from both sides, thus highly nonlocal more than that of entanglement, where the correlations are fixed and can only be changed by a time evolution
(Will check again later if more time to see whether all the above makes sense mathematically)
actually typo: Swap the latter pair of boxes around, otherwise this can be factorised into a product state
Slereah
Slereah
18:00
Hey @0celo7
0celo7
0celo7
18:11
@Mithrandir24601 My solution is to carry a .40 and be ready to put down a posse
@Slereah sup
Slereah
Slereah
Trying to show the time shift in accelerating wormholes
But this requires me to define the acceleration of the mouth
Not easy since for a thin-shell wormhole, there's a discontinuity of the connection there
I think I'll need some sequence of curves converging on both sides
Slereah
Slereah
18:36
I think the proof is then basically just showing that the proper time on both sides is different and so there's a time shift between the two
I think I also need to define some homeomorphism between the mouth at each spacelike hypersurface
To check if the wormhole is "spinning"
0celo7
0celo7
@Slereah ew
connections should be smooth tho
Slereah
Slereah
It's part of the whole Geroch-Tarschen class of metrics
Where the metric is badly regular, but not too badly
You can still get away with using distributions
0celo7
0celo7
@Slereah I thought physicists liked reality to be $C^\omega$
Slereah
Slereah
We also like not to have to solve PDEs that are too difficult
Minkowski space on both side is fairly mild, as far as PDEs go
vzn
vzn
18:54
You Thought Quantum Mechanics Was Weird: Check out Entangled Time / singularityhub
sbp
sbp
19:07
Guys have you heard that Polchinski passed away yesterday? Such a sad news.
This self biography might be interesting for some readers here. arxiv.org/abs/1708.09093
4
0celo7
0celo7
How did we miss Polchinski dying
Slereah
Slereah
RIP Polchinski
0celo7
0celo7
jesus christ, he threw molotovs off the library roof in undergrad
physicists are insane
Slereah
Slereah
was it an experiment
bolbteppa
bolbteppa
wtf
Woah
motls.blogspot.ie/2018/02/joe-polchinski-1954-2018.html
Slereah
Slereah
19:14
"Yes, I am still proud that my surname appears 128 times on a web page of Polchinski's."
Are any of them nice
bolbteppa
bolbteppa
He found 128 errors in the book, it comes off like it was papers or references to his work in the book...
bolbteppa
bolbteppa
19:31
His book is too hard to just jump into, GSW is nicer for a first intro so far, soon will get there properly
Joseph Polchinski
Joseph Polchinski (born May 16, 1954; died February 2, 2018) was an American theoretical physicist and string theorist. == Life == Polchinski graduated from Canyon del Oro High School in Tucson, Arizona in 1971, obtained his B.S. degree from Caltech in 1975, and his Ph.D. from the University of California, Berkeley in 1980 under the supervision of Stanley Mandelstam. After postdoctoral positions at SLAC (1980–82) and Harvard (1982–84) he was professor at the University of Texas at Austin from 1984 to 1992. Since 1992 he has been professor in the Physics Department of the University of California...
Mandlestam
Mithrandir24601
Mithrandir24601
19:50
@0celo7 And if you don't notice until you're lying on the ground, bleeding to death unable to move? (I mean, hopefully that never happens)
0celo7
0celo7
@Mithrandir24601 well, that might happen
so you're saying I should never try to defend myself, just let myself get killed?
Mithrandir24601
Mithrandir24601
@0celo7 no, I'm saying that if someone threatens you, you should do exactly what they want until you're able to run as far and fast as possible. If someone really wanted you dead, you'd be dead - they won't come at you from several paces in front of you openly brandishing a knife (if they do, they're 'just' threatening and we're back to scenario A)
0celo7
0celo7
@Mithrandir24601 I agree for the most part
but if for some reason there's a mob of angry people you might as well do your civic duty and thin the herd
Mithrandir24601
Mithrandir24601
@0celo7 What have you done that you're expecting an angry mob after you?
Anonymous
@0celo7 If there's a mob of angry people coming at you, your duty is to run!
Anonymous
20:01
I don't know the US laws. Maybe you could shoot, but I'm not sure you could justify it to the cops
0celo7
0celo7
If you live in a good state you can stand your ground
especially if it's a mob of people
Anonymous
@Mithrandir24601 That's easy. Telling a bunch of physicists that what they're doing is crap. I wouldn't be surprised if they start chasing 0celo (who is an expert in offending people)
0celo7
0celo7
@Blue I don't think I've ever offended anyone in real life
You people just say stuff that invites offending
Anonymous
You think ? :P
0celo7
0celo7
@Mithrandir24601 walking with a Trump hat in a women's march
bolbteppa
bolbteppa
20:09
Hahn-Banach comes from something like this apparently
user image
Anonymous
I thought the women love Trump and Trump hats...
Anonymous
:P
Slereah
Slereah
Hm
0celo7
0celo7
@Blue not the kind at women's marches
Slereah
Slereah
If I have some timelike hypersurface $\Bbb R \times A$ for the wormhole, and I change the gluing function from $f$ to $f'$ such that the identification of the time coordinate is different
Is it the same wormhole
I'm not sure
I don't think the stress energy tensor depends on the gluing function, but on the other hand if the time shift isn't identical for the same acceleration I think it would be a problem
0celo7
0celo7
20:15
@Slereah I'm having a hard time deciding what a "full proof" should be for my thesis
Slereah
Slereah
The acceleration might depend on that part of the gluing function
0celo7
0celo7
like at what point do I just refer to the literature for some minor result
Slereah
Slereah
@0celo7 Is there a maximum length for thesis
0celo7
0celo7
my advisor said 70 pages but I'm going to way overshoot that
Slereah
Slereah
Well do the reasonable thing then I guess
Don't write the proof if it's 1) well known 2) minor but very long
0celo7
0celo7
20:18
well I'm kind of putting the other proof in there because it isn't well known
but it needs another result
Slereah
Slereah
Also if you overshoot, use the old trick
Put everything in excess in the appendix
0celo7
0celo7
this is already the appendix :(
CooperCape
CooperCape
appendix 2?
0celo7
0celo7
yeah this appendix will probably have to be split up into two parts
it's going to be quite long
CooperCape
CooperCape
Fair, I know nothing about writing things.
Guess I've got that joy to come
or not depending on my failures
0celo7
0celo7
20:22
I could probably have 3 appendices: A. The Cheng-Yau Inequality B. The Laplace-Beltrami Operator C. Coercive Schroedinger Operators
CooperCape
CooperCape
(shit joke incoming)
:coughs: are they Schroedinger operators that don't take no for an answer.
Righto
0celo7
0celo7
schroedinger was a notable sexual deviant
CooperCape
CooperCape
I don't know if that's a joke or not
0celo7
0celo7
@Slereah how do I draw S^2 in tex
and attach a handle
this has to be in some topology book
Slereah
Slereah
Draw a circle, draw two curves for the handle, connect them at each disk by two little bezier curves?
Emilio Pisanty
Emilio Pisanty
20:26
so, I was wondering whether I was the only one to have that idea
twitter.com/search?q=elon+musk+teapot
and I'm obviously not
change.org/p/…
0celo7
0celo7
2-manifolds are so boring
Slereah
Slereah
@0celo7 are they
user image
0celo7
0celo7
compact 2-manifolds I mean
the ones you can draw are tori
Emilio Pisanty
Emilio Pisanty
@Slereah that's horrifying
Slereah
Slereah
true
0celo7
0celo7
20:34
user image
I need to get this into TeX somehow
CooperCape
CooperCape
with the crossing outs? ;p
Slereah
Slereah
You need to master the art of the Bezier curve
CooperCape
CooperCape
I mean you could just go the hard way and shape and place every curve
0celo7
0celo7
@Slereah what is that and where do I acquire it
Cows
Cows
Going hardcore on advance programming techniques. Have interviews with top tech companies next week. Upping my game as best as I can. Been coding and studying practical advanced cs concepts for 2 days non stop. Have passed phone screening first 2 rounds for three companies. They are planning on breaking me on the next ones,
This should be interesting
Slereah
Slereah
20:37
Bezier curves are the standard way to draw weird shapes in vector drawing
They're basically cubic polynomial curves
0celo7
0celo7
u mean splines?
Cows
Cows
Would be interviewing on the campus of a large company on Monday
I am scared!!!!
I have to know so much and be able to demonstrate knowledge on command
this is even worse than the time I had to do qft calculations on the board at NYU
Slereah
Slereah
it's a type of spline, yes
Cows
Cows
hehe
0celo7
0celo7
@Slereah do you have a program in mind for it?
I also need to draw this
Slereah
Slereah
20:40
Most fancy drawing programs have them
I think Gimp has them?
0celo7
0celo7
user image
Slereah
Slereah
But the Tex drawing function also has them
0celo7
0celo7
@Slereah trying to do it in TeX scares me
CooperCape
CooperCape
Could you get someone on tex se to do it or is that a nono
0celo7
0celo7
Dunno
Slereah
Slereah
20:51
What's the 3D equivalent of a string
It's like point particle, string, membrane
And then what
bolbteppa
bolbteppa
2-brane or whatever
Brane
In string theory and related theories such as supergravity theories, a brane is a physical object that generalizes the notion of a point particle to higher dimensions. Branes are dynamical objects which can propagate through spacetime according to the rules of quantum mechanics. They have mass and can have other attributes such as charge. Mathematically, branes can be represented within categories, and are studied in pure mathematics for insight into homological mirror symmetry and noncommutative geometry. == p-branes == A point particle can be viewed as a brane of dimension zero, while a string...
Slereah
Slereah
Branes are surfaces for the boundary conditions, though, not the object themselves
Anonymous
@bolbteppa Is the similarity of the sound of "brane" and "brain" intentional? I had that question for long..
Anonymous
Or does it come from "brane" in "membrane"
Slereah
Slereah
It does
bolbteppa
bolbteppa
21:00
$D-$branes are, $p-$branes are things like strings, brane as in mem-brane :p
Anonymous
en.oxforddictionaries.com/definition/brane
Anonymous
"Origin
1980s: short for membrane."
Anonymous
Cool
0celo7
0celo7
@Slereah they’re the objects too
Avantgarde
Avantgarde
21:20
sup people
Slereah
Slereah
21:38
Nah much
0celo7
0celo7
DNA Test Shows im Jewish
Why the fuck is my phone capitalizing words
Cows
Cows
OOP to the max
Slereah
Slereah
Mazel tov
Cows
Cows
full blown OOP. Got to OOP in 4 langs at exp. Level 5.0 b4 Monday
Dap to lev 2
dev vs cent vc
9.0 ang , ion
Bernardo Meurer
Bernardo Meurer
That doesn't mean anything
Like, there's literally no meaning contained in that sentence
Is this non-chomsky english
Slereah
Slereah
21:56
Like Chomsky makes any sense
Avantgarde
Avantgarde
I can't even hear Chomsky. I have to blow up volume to 400000%. He's always whispering
Bernardo Meurer
Bernardo Meurer
@Slereah He's not that bad, non-chomsky grammars are understandable
:P
@Avantgarde That's true
01:00 - 22:0022:00 - 00:00

« first day (2648 days earlier)      last day (2577 days later) »