« first day (2465 days earlier)      last day (1310 days later) » 

2:54 AM
@BalarkaSen This book gives a new meaning to terse: "Since $\Lambda^*\Bbb R=\Bbb R\oplus \Bbb R$, it follows that if $e_1,e_2,\dotsc$ form a basis of $V$, then the products $e_\lambda=e_{\lambda(1)}\wedge\cdots\wedge e_{\lambda(m)}$ corresponding to all inc. $m$ termed sequences $\lambda$ form a basis of $\Lambda^mV$." What?
 
What was your old meaning of "terse?"
 
@skullpatrol It's a saying
 
I know, I'm joking.
> ::back to watching football::
 
::sips Maker's Mark::
@BalarkaSen this is awful
 
3:26 AM
@BalarkaSen I mean for finite dimensional ones, I guess you need $V=\Bbb R\oplus \cdots\oplus\Bbb R$ and then some combinatorics/induction, but for infinite dimensional ones...
 
 
1 hour later…
4:31 AM
@JohnRennie Oh man, the irony is too sweet
My CPU overclocker is using more CPU power than it gives
 
:-)
 
@JohnRennie Did you see my messages about my SSD?
 
Yes. The best solution is to ban you from running benchmark software :-)
 
Did you read Gowers' web blog, sir?
 
4:48 AM
@JohnRennie Also it turns out that overclocking your CPU in the middle of playing a game is catastrophic
who knew
I'm running a powerful GPU overclock though.
420 MHz
Bernardo has dared me to get 470 stable
 
@TheRaidersofLasVegas Me? If so, no, Gowers is a mathematician not a physicist and his blog is far beyond me.
 
It was about the monopoly of the publishing companies.
 
Ah, OK, yes I had seen that.
 
5:16 AM
@JohnRennie So if 3200 MB/s is advertised and I get 1500, that's not an issue?
Especially if I got 3250 yesterday?
 
Somebody talking about IO?
 
5:57 AM
@0celóñe7 Not the world's most beautiful exposition on the exterior algebra.
 
6:37 AM
What is the most beautiful exposition of elementary algebra that you've seen? @BalarkaSen
 
7:10 AM
@Nik: hi :-)
 
Nik
 
In your system the water levels will always be the same on both sides.
 
Nik
thanks John...
 
So the levels will rise until they reach the top of tank B, i.e. tank B is full, while tank A is still only half full.
Well, this assumes you fill the tanks slowly.
Suppose you pour water into tank A faster than the water can flow along the pipe to tank B.
In that case it would be possible to temporarily fill tank A first. But obviously if you sit back and wait the water levels will equalise.
 
Nik
yup.. understood!
 
7:20 AM
@Nik sorry for closing your question but we have very strict rules about anything that looks like a homework problem even if it wasn't actually set as homework. We have to do this otherwise we'd be swamped by students trying to cheat on their course work!
But we're happy to discuss things like this in the chat room and there's usually someone around willing to help.
 
Water is a fun one.... non compressible...
I used to work for a water company, controlling pumps and res's and such
When you're controlling some pumps that move 800l/s you've got to think about where that water is going ;)
(4x)
 
8:03 AM
-1
Q: Where i can found info about next international meetings in General Relativity

needvedI looking for Events or International Meetings dates in the period September 2017-August 2018. Meetings focused on General relativity, Gravity Waves and Cosmology. Someone knows where i can check this issue. I apologize if this topic is forbidden here, I have not seen the rules in depth Thank...

 
 
2 hours later…
9:49 AM
since ACM left this chat is dead
ACM PLEASE COME BACK
 
2 days ago, by ACuriousMind
@0celóñe7 I'm in Wacken, expect to see little of me here until Sunday
 
any $g\in L^p$ defines a tempered distribution, right? as in, $f\mapsto \int f(x)g(x)<\infty$
 
 
2 hours later…
11:41 AM
@AccidentalFourierTransform Sure, use Holder.
@AccidentalFourierTransform the map L^p --> S' is even continuous.
@BalarkaSen Do you know how what he claims follows from what he says?
 
12:22 PM
@0celóñe7 well that was easy
:-P
thx
 
Hi all,
 
Are we allowed to post doubts here on chat box?
 
Physics related doubts,I mean. ☺
 
12:26 PM
:D
yes, yes you can
but there is no one online rn who knows a thing about physics
 
It is given in my text that a loop (made up of a flexible wire) of irregular shape carrying current located in an external magnetic field changes it's shape to that of a circle in order to maximise the magnetic Flux. But I am having doubts on why actually the Flux needs to be maximized. Can anyone make it clear?
 
@dmckee Interestingly, what really attracted me the most about this is the small size of their instrument. I wonder if other particles can have such small sized detectors, or will it be only limited to weakly interacting particles...
 
@ACuriousMind I can't believe you
What a horrible person who disappears for a week and deprives me of sending them cat pictures
@ACuriousMind He is walking in front of me right now!!
 
Figure 3 seemed weird, near the end, the two peaks shifted to the left slightly, not sure if real or instrument noise
and pretty pictures of a stormy Neptune
 
12:45 PM
that looks like a baby ultrasound
u preggo?
 
The electromagnetic field continues to feel weird.
 
@AccidentalFourierTransform thanks!
 
If the electromagnetic field continues to feel weird after four hours, call a doctor.
 
@AccidentalFourierTransform why are you obsessed?
 
1:02 PM
Drew me the more beautiful feymann diagram that makes no sense
 
1:12 PM
0
Q: the way space-time deforms

GamnamnoIt seems spacetime is not bending but instead deforming into itself. In an illustration with a 2D universe, space is not deforming like this : which would require a 3rd dimension, but rather more ore less like this : If that's right, then how could a wormhole not make intersections along th...

O, and this question helped debunked one of my thoughts about intrinsic curvature, turns out plotting wormholes with that model will be a counterexample
So that means, spacetime curvature is actually pretty abstract...
 
1:34 PM
Liberalism is anti science — John Jul 30 at 3:34
in case you guys didnt know
 
Will a magnet deflect if kept under electric supply lines ??
 
@AccidentalFourierTransform correct
 
shut up you dont even know what liberalism means
america is so weird
you dont know what words mean
Modern American liberalism is the dominant version of liberalism in the United States. It is characterized by social liberalism, and combines ideas of civil liberty and equality with support for social justice and a mixed economy. The term "modern liberalism" in this article refers only to the United States. In a global context, this philosophy is usually referred to as social liberalism. The American modern liberal philosophy strongly endorses public spending on programs such as education, health care, and welfare. Important social issues today include addressing inequality, voting rights for...
 
1:56 PM
[List of path integrals that probably make no sense]
 
\begin{align}
\int F(f)d[f] = 1 (\text{Definition of probability distribution})\\
\langle f\rangle = \int F(f)fd[f]\\
\langle f \rangle=\sum_{i=1}^N F(i)f_i\\
\langle f\rangle =\int F(f)fd[f] = (\int g(x)dx)(f)\\
\langle f\rangle = \int F(f)fd[f] = \int e^{T}fd[f]
\end{align}
 
Jul 21 at 19:57, by AccidentalFourierTransform
$[d\phi],\mathscr D \phi,\dots$ is just stupid notation
 
line 3 is when the probability distribution is discrete and finite
line 4 is when it is some integrable function $g$ and the set of f is given by $g*f$
line 5 is when the set of f is given by applying a continuous transformation to f
 
What should the notation be @AccidentalFourierTransform
Ideally one never deals in such poorly defined concepts though
 
2:01 PM
$\mathrm d\phi$
 
If these are not path integrals (since the integration variable is clearly a function), then treat them as probability distribution over a continuum of random variables
and almost forgot: $F: L^2(\Bbb{R}) \mapsto [0,1]$ is a probability distribution whoose random variable are integrable functions
 
You never ever want to work on L^2
Use a Sobolev or Lipschitz space
 
Is there a symbol for the space of all (Lesbegue) integrable functions?
 
@AccidentalFourierTransform why not a capital D
@Secret L^1
 
Anonymous
@GauthamShankar It might if it is not already aligned with the magnetic field.
 
2:06 PM
but yeah, I think I will stick to Sobolev or Lipschitz now, cause $L^1$ might have issues
 
@0celóñe7 bc thats a derivative dummy
 
@AccidentalFourierTransform and d isn't?
 
¯\_(ツ)_/¯
 
Where the hell is @ACuriousMind
 
He is in Wacken
4 hours ago, by skullpatrol
2 days ago, by ACuriousMind
@0celóñe7 I'm in Wacken, expect to see little of me here until Sunday
 
2:17 PM
I don't know what that means
 
Actually, on a deeper thought, since an ordinary lesbegue integral acts linearly on functions, it is a linear map in the vector space of functions
So perhaps, a path integral is a linear map on the vector space of functionals
 
Wacken is the biggest heavy metal festival in the world @0celóñe7
Wacken is a municipality near the town of Itzehoe in Schleswig-Holstein, Germany. Wacken was first mentioned in 1148, but there were probably some settlements before, which is proven by the trove of Germanic artefacts. Today, Wacken is famous for annually staging the world's biggest open air metal festival, "Wacken Open Air", which has hosted popular metal acts such as Iron Maiden, Saxon, Alice Cooper, Deep Purple, Mötley Crüe, Slayer, Rammstein, Motörhead and Judas Priest. The festival is held in July and August, a period which often has stormy weather in that area. Due to the festival the entry...
 
Slereah: Can we define path integrals as linear maps in the vector space of functionals?
 
is ACM a metalhead?
 
2:25 PM
he is a heavy metal fan
 
huh, thats kinda unexpected
dunno why
never pictured him that way
I thought he hated music and anything that is fun tbh
 
he had mentioned in the past before he went to last year's Wacken
 
2:53 PM
@AccidentalFourierTransform he likes video games
But only bad ones
 
Dat
hi
 
hallo
@0celóñe7 bad example, video games are not fun
 
vzn
at ORNL!
@AccidentalFourierTransform such a constant @$^& joker its amazing you have any rep. that reminds me, need to write up silly onion articles on physics in blog sometime...
 
3:12 PM
Keep up at the back there :-)
 
Consider the following weird metric:
$$ds^2 = -tdt^2+dx^2+dy^2+dz^2$$
 
@Secret what about it?
Is that not isometric to Minkowski?
 
it has the weird property that over time, space remains flat, but time get progressively more dilated (supposing I actually interpret this properly)
Think a FLRW metric but only the time component is "expanding"
uh, I don't think it can be isometric to minkowski, cause of that extra t factor that make the $dt^2$ nonlinear...?
 
3:29 PM
what if $\tau\equiv \frac23 t^{3/2}$
 
I think we are still off:
$\tau\equiv \frac{2}{3} t^{3/2} \implies \frac{3}{2}\tau^{2/3}\equiv t \implies \tau^{-1/3}d\tau = dt \implies \tau^{-2/3}d\tau^2 = dt^2$

$-tdt^2 = -\frac{3}{2}\tau^{2/3}\tau^{-2/3}d\tau^2 = -\frac{3}{2}d\tau^2$
unless we can scale the whole metric without changing the physics?
 
Just let d tau = t^1/2 dt
Integrate.
That's a smooth transformation away from t=0, which isn't in the manifold anyway
@Secret yes
Well...with a coordinate transformation
 
@Secret Your calculations are all wrong. Like, the very first implication.
 
ah yes, that fraction 3/2 will get a 2/3 power
 
No need to do that. $d\tau = t^{1/2} dt$ just from differentiating the first thing.
This is just basic calculus.
$d\tau^2 = t dt^2$ like AFT and 0celo said.
 
Anonymous
3:43 PM
Is anyone being able to access this link <http://wiki.scilab.org/Ideas_of_development_for_Scilab> ? Don't know why it is not working
 
Anonymous
I am trying to contribute to Scilab's page for Google Summer of Code...no that's not a virus :P
 
Anonymous
Oh..it's down
 
Anonymous
Thanks
 
A TIP : Any metric of the form $-f(t) dt^2 + dx^2$ is isometric to Minkowski space
 
3:46 PM
yeah, I was trying to rearrange to dt^2 so I can sub directly, but I made too many careless mistakes along the way, should have just differentiate and then rearrange
Ok so...:
 
Anonymous
 
Anonymous
Probably this is the reason :/
 
Also another tip : any flat metric is gonna be related to Minkowski space
 
are @Blue and OBE the same person?
 
For one of the inertial frames, space expanding linearly along the x,y,z direction as time progress will be given by the following metrics:

\begin{align}
ds^2 = -dt^2+tdx^2+dy^2+dz^2\\
ds^2 = -dt^2+dx^2+tdy^2+dz^2\\
ds^2 = -dt^2+dx^2+dy^2+tdz^2\\
\end{align}

(and of course, rotate to another inertial frame via a lorentz transformation should give me mixed terms so that both space and time will be curving when seen in that frame)

Now how can I make it bend only in time as seen from one particular inertial frame...?
 
Anonymous
3:50 PM
@AccidentalFourierTransform Nope. OBE is a subset of Blue.
 
Anonymous
:P
 
vzn
@JohnRennie yeah scooped by the physics phd prof. anyway a popsci article/ summary for anyone around who doesnt look down on those. :| ps has 0celo7 said anything about it?
 
Anyway, the metric I want, in words is like this:
A and B are moving relative to each other, A see B getting more progressively time dilated as the proper time went by
similarly, B had the same conclusion
Yet there are no change in distance (? o wait, is this making sense, cause they are supposed to be moving relative to each other...) in between them
But in a nutshell, I want a metric that describe a spacetime where to most reference frames, globally the time dilation grows in magnitude, if that makes sense...
 
@vzn what?
 
vzn
3:57 PM
> The Spallation Neutron Source facility, which also produces lots of neutrinos.
↑ guess thats an inside/ ironic semi joke? 134 over 15 months?
 
@vzn 134 is the number of observed coherent scattering events not the number of neutrinos. The number of neutrinos is of order $10^{20}$ per day.
 
vzn
@JohnRennie ok, but thats kind of the point eh? apparently only a very tiny percent of those "theoretically" generated are detectable... (as bohr might insist, if you cant measure it, you cant say it happened...!)
 
Possibly something like this...
Now it is clear if we rotate into the O' frame, this will translate into a mix of space and time expansion
 
@vzn the probability of coherent scattering with a nucleus is very small. The point is that it's large compared to regular neutrino scattering as measured at Kamiokande et al.
 
So I guess, I can first start with the metric written in the coordinates of the O' frame and then transform back to O to get the explicit form I want to see...
 
4:05 PM
That's why you can get statistically significant measurements with a 2kg detector rather than a mofo tank of water.
The point is not to measure the neutrino emission. The point is to prove those neutrinos can be detected using coherent nuclear scattering.
i.e. that this type of detector is experimentally useful.
 
vzn
@JohnRennie ok, so, a different approach, like a "low budget" detector. except its probably still rather high budget apparently. they apparently still have a lot of shielding/ support facility. it would be interesting to compare budgets.
 
wish there are similar small sized detectors for other particles as well, though I guess their action will mean the probability will be too tiny
 
vzn
@JohnRennie dont quite understand your distinction, not exactly following. how is detection different than measurement?
 
@vzn I've been there, yes
 
vzn
@0celóñe7 tour, did you like it? maybe you care exactly one neutrino worth for experimental science, like many other (even physics) topics? :|
 
4:10 PM
@Secret The trick with most particles isn't detecting them—individual detector elements can be less than a centimeter on a side—it's knowing what you just detected.
 
@vzn I'm afraid I don't understand what you are asking. The $10^{20}$ neutrinos are a side effect of the neutron source (the SPS). The SPS wasn't designed to produce neutrinos. It produces them because neutrons produce neutrinos when they decay.
 
In the context of a LHC experiment that means disentangling dozens or hundreds of particles that appear during a single bunch crossing.
 
The point of the experiment is to prove the detection method works, which it does.
 
@JohnRennie It also validates the theory used on neutrinos.
 
vzn
@JohnRennie spking of Kamiokande, not up on that, has it generated non-null results? its still ramping up or something?
 
4:11 PM
And that's exciting because as a detection method it's vastly simpler and cheaper than anything that has gone before.
@dmckee @vzn as dmckee says, this type of scattering has not been observed before so that's another big win.
 
vzn
@JohnRennie dont understand difference/ distinction you seem to be making between "measuring neutrino emission" and "proving neutrinos can be detected..."
 
Proving neutrinos can be detected cheaply and easily
 
@dmckee So the more complex the process of sifting through the data is, the larger the detector array has to be?
 
vzn
@JohnRennie its presumably still a multimillion $ experiment afaict...?
 
We've been detecting neutrinos expensively and with difficulty for half a century
@vzn no
 
4:14 PM
@vzn just a tour. I'm a user at HFIR
I don't see much use for neutrinos
 
@Secret It's not so much size as the ability to differentiate different things, which means you need to get different behavior from different particles.
 
vzn
@0celóñe7 hmmm, maybe they have something to do with very abstract math. or not. (spking of which, some dont see much use for very abstract math...) any reaction to the tour?
 
The LHC detectors are big because measuring the momentum of particles with tens or hundreds of GeV kinetic energy take space when you can only muster a magnetic field of a few Tesla.
@JohnRennie We've also had 10=100 kg scale neutrino detectors for very high fluxes (right by reactor cores) for a decade or so. They are being considered for part of the internation effort at policing nuclear non-proliferation compliance.
But those are relatively low precision devices not suitable for doing science—just for validating that people aren't making un-scheduled changes to reactor configurations.
 
vzn
@dmckee so wouldnt they only be useful by bringing the detectors right next to the reactors? ie by compliance cert teams?
 
@vzn I don't see any use for abstract math either
 
4:19 PM
At this point it is basically pure science (except the non-proliferation deal I mentioned to John).
 
I don't think the government has any business funding it
 
vzn
@0celóñe7 ah lol a somewhat Hardyesque sentiment although maybe not as thoughtfully philosophical as his... admit being a fan (he worked in number theory, great mathematician... you might enjoy the recent movie, liked it) vzn1.wordpress.com/2016/05/10/…
 
What did he say that was more philosophical
 
vzn
@0celóñe7 he has some semifamous sentiments (quoted/ cited in my blog in places) along lines that number theory had no application eg at least cant be used used in warfare. (he was a pacificist, a peer of Russell...) those sentiments turned out not to be exactly correct in retrospect. very much math eventually finds applications although sometimes decades after 1st investigated...
@0celóñe7 what are you referring to? SNS neutrino detection?
 
More interesting stuff happening in neutrinos: t2k-experiment.org/2017/08/t2k-2017-cpv.
Mind you, 2+ sigma isn't enough to declare victory, but it is more than enough to send the theorists scrambling to deduce consequences.
I think there was a question on that recently, too.
 
vzn
4:33 PM
@dmckee wondering when Kamiokande started generating events
 
Yes. there was a question. And I answered it with the orthodox response, too.
Isn't science great?
 
@vzn A word on nomenclature. "Kamiokande" means an experiment that finished long ago and was torn out to make room for KamLAND. The far detector for T2K is called "super-kamiokande" (or just "super-k").
 
Note that the original Kamiokande detector has been superceded by super-Kamiokande.
Damn. Ninja'd :-)
 
vzn
ok, googling, maybe was thinking of IceCube/ AMANDA which are more recent
 
5:13 PM
@vzn abstract math
@JohnRennie how to cure benchmark addiction?
I'm not even home and I'm thinking about benchmarks
 
@0celóñe7 there is no cure :-) I still run benchmarks after 40 years of playing with computers.
 
Anonymous
6:09 PM
@0celóñe7 Buy cheap devices...you'll not even feel like benchmarking anymore
 
6:20 PM
@dmckee to be fair, -1 sigma is enough to send theorists scrambling
 
@JohnRennie my 2D graphics score is really low :<
@Blue I did
 
Anonymous
6:35 PM
@0celóñe7 Which?
 
@DavidZ ::chuckles::
There is some of that.
The scrum following the initial OPERA velocity announcement was a sight to see.
 
6:50 PM
@dmckee Yay! Just in time for me to start a PhD in (C)PT symmetric Hamiltonians :D
2
 
Anonymous
7:07 PM
@Mithrandir24601 Starting your PhD soon?
 
Anonymous
Congrats!
 
7:42 PM
Hey. The footer on the site changed. I'm not at all sure that I approve.
 
Anonymous
@dmckee Doesn't look bad :P
 
I can't see the difference.
 
@Blue Looks fine, but it messes with my workflow.
 
Anonymous
hehe..;P
 
Actually, with all the scripty magic that seems to be there is isn't as bad as I feared. But it still double the number of clicks I have to make for opening my 'check once a day' sites from one of my 'look at fairly frequently' tabs.
@0celóñe7 What I see is
 
7:49 PM
Yes.
What did it use to be?
 
when there used to be a bunch of sites broken out under those same catagories.
Ah. Found a tab old enough to have the previous layout:
 
Huh.
 
That's from arquade, but all the sites were similar.
I gotta admit the new version is cleaner, but I was used to the old one. I had it figured out.
 
can someone tell me what happened to Hall's theory of metallic conduction pnas.org/content/12/5/326.full.pdf ?
 
@dmckee I don't think I've ever looked at the bottom of a page.
@BernardoMeurer I tried to play CS:GO for a minute and got destroyed
Apparently you have to buy guns
What is this nonsense
 
8:25 PM
@Blue I've already started my PhD, but haven't started my main PhD project (we have a year before hand where we do other stuff like essays, exams and smaller projects)
 
Anonymous
8:41 PM
@Mithrandir24601 Oh. Good luck with that =P
 
vzn
11:26 PM
@Mithrandir24601 congratulations! you are now officially overqualified for a Physics AMA (hint, hint) :)
@0celóñe7 the govt doesnt fund it much )(... happy now? :P
 
@vzn Well, I'm away from the 15th August until the end of that week. Almost any other day suits
Why is it that if you're not under-qualified, you're over-qualified? :P
 
vzn
@Mithrandir24601 uh are you talking about AMAs or something else?
 
@vzn General comment on life, I suppose
 
vzn
@Mithrandir24601 looks like next mtg with some lead time is aug22...? regular mtg time is tues 1600Z
@Mithrandir24601 so do you want to do your Phd on CPT?
 
@vzn Sort of... Simulating PT symmetric Hamiltonians (which seems to include CPT symmetric Hamiltonians) on a quantum chip. The actual title (at the pre-research stage) is Simulating models on the boundary of quantum physics
 
vzn
11:37 PM
@Mithrandir24601 way cool stuff! did you say earlier 8qubits? thats more than IBM at the moment (5)... what school is that?
 
@vzn By the time I actually start (I'm told we should actually have it by now, but I can't guarantee that) we can apparently have 8 qubit chips, but I don't know if they're universal or not (i.e. they might have to be fabbed individually for each experiment, will the gates 'hard-fabbed' [my term, as I can't think of what else to call it] in which is a bit of a nuisance)
we will apparently have an 8-waveguide universal chip. This is at least 3 qubits, but apparently, there are things you can do to get more qubits from the same number of photons. Again, I don't know if you can do this on a universal chip... IBM actually has 16... I'm at Bristol :)
Although, there's no reason that I know of that I can't use IBM's chip(s) for it as well
 
vzn
11:57 PM
@Mithrandir24601 youve met DS on here right?
 

« first day (2465 days earlier)      last day (1310 days later) »