The h Bar

Slereah

16:00

The Dirac sea wasn't a bad idea in itself, really

But it doesn't work for photons

Theories with no ground state end up poorly

Gaurav

Why do some people edit posts to reformat equations into latex when they vote to close it just after editing ?

John Duffield

@Danu : negative gravitational energy misleads many even now. Ditto for binding energy in general. Invariant mass varies.

FenderLesPaul

Ooh free lunch

I want a free lunch

ACuriousMind

@Slereah huh? Theories without a ground state are pathological anyways

Slereah

@Gaurav LOVE OF A WORK WELL DONE

@ACuriousMind That is what I said, yes

ACuriousMind

16:03

@Gaurav I think they might be doing it to show the OP that we have LaTeX here for further questions they might ask, but perhaps they're just a bit obsessive :P

Gaurav

@Slereah You mean work that earns you reputation ? ;)

ACuriousMind

@Gaurav Editing above 2000 rep doesn't give reputation.

Gaurav

@ACuriousMind Oh, that I didn't know

FenderLesPaul

Oh no I creased my copy of Straumann

GOODBYE CRUEL WORLD

Slereah

How do you crease that book

FenderLesPaul

16:08

I BARELY KNEW YE

Slereah

It's like a brick

FenderLesPaul

mine is paperback :(

Slereah

I am hungry

Let's go to the supermarket and make some crepes

brb

0celo7

Mine is hardback

ACM can find the picture of it

Gaurav

Quick show of hands: who loves the smell of a new book more than what's actually written in it ?

FenderLesPaul

16:22

tumbleweed rolls by

John Duffield

16:32

@FenderLesPaul : I'm busy answering physics questions.

FenderLesPaul

@JohnDuffield cool

0celo7

16:53

@ACuriousMind lol stop your targeted downvoting of poor answers!

ACuriousMind

@0celo7 :P

John Duffield

@0celo7 : mine are good answers. Your comments demonstrate that you will benefit from your further education. Meanwhile, if you have any questions, please ask, and I shall give you the benefit of my expertise.

ACuriousMind

Random thought: I think we should add a caveat to Jimself's guide to trolls that "don't engage" is also valid if the troll is not actually technically proficient.

3

Slereah

Really the annoying thing isn't so much that Duffield is wrong, it's that his answers are usually unrelated to the questions

John Duffield

@Slereah : my answers are directly related to the questions. See this example. And my answers aren't wrong either.

FenderLesPaul

17:08

That's a perfectly fine answer but why use Einstein as the main reference?

modern textbooks exist for a reason

Einstein may have had the brilliance to come up with GR but he had A LOT of misconceptions about GR

so using him as the go to reference isn't going to help the OP

ACuriousMind

"Think of matter as light going round and round, then simplify it to a square path."...wat

John Duffield

@ACuriousMind : who are you calling a troll? My answers are good answers. I am technically proficient. And by the way, I don't hang around closing down questions and carping at the people who do give answers.

@FenderLesPaul : because Einstein was the author of general relativity, because there are some issues with some textbooks (see what I was saying to 0celo7 earlier) and because they aren't online. Einstein did NOT have a lot of misconceptions about GR. 0celo7 does. And some of the other people around here.

FenderLesPaul

Sorry that's just plain wrong

if you're going to argue then you should at least present proper sources

0celo7

I have misconceptions :(

ACuriousMind

@0celo7 You do, but GR is not among them ;)

0celo7

17:14

The math symbols look so pretty though

FenderLesPaul

it's a ubiquitous well known fact that historically Einstein did not understand GR very well at all, at least not in its early days which are in the time range that your references are from

0celo7

@ACuriousMind speaking of GR I still have not calculated the Kerr black hole collision thing

ACuriousMind

I just edited a question where OP had surrounded every single word with dollar signs. WTF

John Duffield

@ACuriousMind : yes. The wave nature of matter is not in doubt. Nor is the Einstein-de Haas effect. Nor are atomic orbitals where electrons "existing as standing waves". Nor is the Poynting vector.

0celo7

Lol

FenderLesPaul

17:16

Honestly you can believe whatever you want, all the power to you, but it's just not cool to propagate misunderstanding in the minds of people who genuinely don't know any better and can't tell personal speculation from established theory

ACuriousMind

@0celo7 I remember that faintly...what was the question?

0celo7

@ACuriousMind smash two Kerr black holes in an axisymmetric configuration and find an upper limit on the mass that can be radiated away

ACuriousMind

ah

obe

@0celo7 Is it cool if I use Lee to learn about manifolds because Carroll's description isn't very useful to me.

0celo7

Lee is a lot longer and more detailed

Also he does not cover Riemannian geometry

John Duffield

17:20

@FenderLesPaul : I'm not propagating misunderstanding. I'm dispelling it. Those references are not early references. The first one in my "perfectly fine answer?" dates from 1920. People like 0celo7 don't even know the difference between curved spacetime and curved space.

obe

@0celo7 Reference for Riemannian geometry then (for later)? Do Carmo's book?

0celo7

Jesus Christ I misread a word and apologized for it.

ACuriousMind

@0celo7 Just ignore him.

0celo7

@obe I think HE is good for geometry honestly

ACuriousMind

@0celo7 Riemannian? What would that be for? We need Lorentzian, right?

FenderLesPaul

17:21

@JohnDuffield whatever makes you happy man

0celo7

@ACuriousMind damn. I don't know any GR I guess

ACuriousMind

@0celo7 Just saying because reading a book on Riemannian geometry will contain many things which simply don't work in the Lorentzian case

0celo7

@obe do carmo is used in the first geometry class at UTK, it covers a lot stuff you'll never need

@ACuriousMind hmm, like what? I've never systematically learned Riemannian geometry without physics in mind

obe

@0celo7 What is a good differential geometry text to compliment carroll that contains all the aspects of geometry that I need?

ACuriousMind

@0celo7 That the path length gives a metric on the manifold, that every geodesic minimizes the length functional, Hopf-Rinow theorem...

0celo7

17:25

@ACuriousMind I knew that, that can be adopted (see HE), what

John Duffield

@0celo7 : note that people who say "just ignore him" can't explain why what I've said is wrong. That's because it isn't.

ACuriousMind

@0celo7 I know there are Lorentzian variants, but reading about Riemannian geometry will not teach you those, unless it's also pseudo-Riemannian

0celo7

@JohnDuffield we do explain why you are wrong but you just close your eyes and link to Einstein

The best we can do is downvote you at this point because you won't listen.

@obe read chap 2 in HE, see if that makes more sense to you

obe

@0celo7 I only need basic calculus and algebra right?

0celo7

@ACuriousMind ok, stop being so nitpicky :/ a lot of Riemannian can be carried over

@obe for that chapter, yes.

ACuriousMind

17:31

@0celo7 Dude, I'm like, the master of nitpicking

That's why y'all love me

FenderLesPaul

picks nit

0celo7

@obe maybe Nakahara

obe

@0celo7 :D :D :D

John Duffield

@0celo7 : no, you don't explain why I'm wrong. Your recent comments on my older answer demonstrated a poor understanding. So much so that you even deleted one of your comments. Do not think you know better than Einstein.

0celo7

Skip the chapters on topology

obe

17:32

@0celo7 Will do.

0celo7

@JohnDuffield I did not demonstrate a poor understanding. You demonstrated not knowing what a gravitational field is.

FenderLesPaul

Dude just let it go lol

0celo7

@FenderLesPaul no

FenderLesPaul

@0celo7 fite me

0celo7

@FenderLesPaul you're like a million miles away now

Slereah

17:37

>not early references

>1920

top kek

John Duffield

@0celo7 : I know what a gravitational field is. You don't even know the difference between curved spacetime and curved space. You don't know that a gravitational field is a place where space is inhomogeneous, not curved. You said "that's nonsense", even though that's what Einstein said in 1920.

Slereah

I think by 1920 they didn't even resolve the controversy of gravitational wave energy

0celo7

So everything Einstein said is 100% correct all the time?

FenderLesPaul

This is just a fruitless conversation lol

Slereah

How many GR solutions existed by 1920 I wonder

Schwarzschild existed

Gravitational waves also

The Einstein universe, maybe?

Gaurav

17:40

@FenderLesPaul Hush ! I just got popcorn , don't waste my money.

0celo7

RN

Slereah

ah yes

1917

What else could there be

De Sitter, probably

1917 as well

Damn, Kerr was in 63

0celo7

Yup

Slereah

Nordstrom was in 1917 by comparaison

FenderLesPaul

Yeah Kerr took a while

Slereah

17:43

shit was hard

0celo7

Einstein did not even know about rotating solutions

Slereah

Let's see the Tomimatsu metric

ACuriousMind

Gödel's weird thing was '49

John Duffield

@0celo7 : no, Einstein wasn't 100% correct all of the time. However if your textbook says matter tells space how to curve but you can read Einstein saying a gravitational field is inhomogeneous space, you know you've got an issue, don't you?

Slereah

The rotating cylinder dust was 36

Why would that be an issue

Modern day GR predicts every effect associated with gravity

0celo7

17:45

@JohnDuffield The only issue I see is Einstein giving the wrong definition of the gravitational field...

Slereah

It matches all current experiments

NeuroFuzzy

@Slereah Hehe wouldn't you say that's pretty glaringly false w/ dark matter? Not to hijack your point :p

0celo7

There is no such thing as dark matter. Your mom is just so fat GR can't handle it.

John Duffield

@0celo7 : it wasn't wrong. Space is not curved in the room you're in. See that Baez article. Your understanding is wrong. Follow my links, do your own research, and think for yourself. Now do excuse me, I have to go.

ACuriousMind

@NeuroFuzzy The matter content is an input to GR, why would that be false?

NeuroFuzzy

17:50

@ACuriousMind Oh. Right.

ACuriousMind

@JohnDuffield Don't let us detain you.

0celo7

@ACuriousMind Did you win the RPG?

ACuriousMind

@0celo7 That question does not make any sense ;)

0celo7

Did you slaughter your foes and get the wenches =: victory?

ACuriousMind

@0celo7 No, because I am the game master, not a player

0celo7

17:56

What does that entail?

ACuriousMind

@0celo7 Well, every player controls their own character. I control...essentially everything else

0celo7

So you could kill everyone and claim victory and wenches, no?

ACuriousMind

The game master is nature, the gods, their foes, the random passer-by, the merchant they sell their overpriced loot to,...

0celo7

This seems really complicated

ACuriousMind

@0celo7 But...I am not a character. I don't have an objective, I am just there to let the world react to the players' (in-)action

0celo7

17:59

You're like a god and they can certainly do all that and claim wenches.

ACuriousMind

@0celo7 Yes, but where would the fun be in that?

Precisely because the GM is all-powerful, they need to be careful not to ruin things for everyone. Telling the story in an enjoyable way, and properly reacting and improvising to the players' actions is an art in itself.

0celo7

Zeus certainly had fun.

skull patrol

How many players?

0celo7

1 after ACM is done with them.

ACuriousMind

@skullpatrol Typically 4-6, though I've seen from 3 to 10

0celo7

18:02

@ACuriousMind turns out I have been to Heidelberg.

Stan Shunpike

Who uses the word wench anymore?

skull patrol

:-)

0celo7

@StanShunpike Skyrim game files. I've had a lot of experience with them.

Stan Shunpike

Ah

That explains it

ACuriousMind

@0celo7 Unless you play hardcore D&D, it's not meant to be an antagonistic "GM vs. players" experience

There's fun in the tactical intricacies of D&D combat, but it's really not representative of what RPGs are meant to be

@0celo7 Sightseeing?

0celo7

18:05

@ACuriousMind our beach wood furniture was sold by a Danish firm out of there. They had a showroom.

skull patrol

How is beach wood any different than wood grown in a forest?

Or perhaps I should say taken from a forest :P

NeuroFuzzy

Just a double check, would you say the OP's reasoning is correct and it's an example of a dumb sparknotes SAT question? physics.stackexchange.com/questions/200565/…

Danu

@ACuriousMind It's very similar anyways

0celo7

Beach is a type of tree

Buche

Danu

@obe You don't need a real math book at all to learn physics-GR

ACuriousMind

18:10

39 mins ago, by ACuriousMind

@0celo7 Dude, I'm like, the master of nitpicking

0celo7

@ACuriousMind apparently I've been to the castle on a school trip but I don't remember that

TanMath

Hello @DanielSank ? Sorry for disturbing you, but r u available today?

ACuriousMind

@0celo7 Oh, you saw the big barrel!

Danu

@Slereah :D

0celo7

@ACuriousMind perhaps. I need to look at pictures when I get home to jog my memory.

Danu

18:14

@ACuriousMind Naturally

ACuriousMind

@Danu Oh, I also have groups where I'm a player.

skull patrol

Are you an active member at RPG.SE @ACuriousMind?

ACuriousMind

@skullpatrol Nope, although I like many of their system-agnostic questions

skull patrol

I need to go visit their chat room one day...

DanielSank

@TanMath I'll respond to messages.

But as I say all the time

I see online chat as an asynchronous communication protocol.

Hi, @cryonole.

cryonole

18:23

Hi @DanielSank

ACuriousMind

(It's true, he says this all the time)

Danu

@ACuriousMind No, you say that he says it all the time

ACuriousMind

For a value of "all the time" smaller than 10

cryonole

So I am looking into MatLab literature mathworks.com/help/curvefit/smoothing-splines.html

DanielSank

@Danu LOLOLOL

@ACuriousMind It's a reasonable fraction of the messages in the link you just posted :P

cryonole

18:25

its like minimizing least squares and an additional penalty function

DanielSank

@cryonole Step back a minute, dude.

cryonole

sure

DanielSank

Why are you using a spline at all?

Just smooth the data with an averaging window.

cryonole

i've tried that

DanielSank

Then it's turbo easy to compute the uncertainty.

@cryonole and?

cryonole

18:26

i need a lot of smoothing where fluctuations in the curve are large, and then this excessive smoothens the data where the trace changes sharply

DanielSank

@cryonole k

cryonole

like at places when the signal just starts to increase above 4.2 K

DanielSank

The reason I don't like the spline is I have no idea how it works, so I have no idea how to propagate the uncertainty.

@cryonole Yeah, I get that.

By the way, what is this data?

cryonole

temperature

vs time

DanielSank

Yes, duder, I get that.

What is it?

Doing something with helium?

cryonole

18:28

its the temperature of a copper tube cooled by LHe

yes

DanielSank

Okay, just wondering.

Why do you care about the uncertainty?

The fitted spline is pretty damn smooth.

cryonole

so I need to obtain rate of change of energy of the tube

that is rhocdT/dt

DanielSank

You can use math notation here.

cryonole

$\rho C dT/dt$

now how does that work here?

DanielSank

Go here.

Drag the "start chatjax" link to the tab for this page.

'sup, @ChrisWhite?

cryonole

18:31

$\rho C dT/dt$

nope

still don't get it

DanielSank

You dragged the "start chatjax" link and dropped it on the tab for this chat room?

What browser are you using?

ACuriousMind

Add the start ChatJaX link to your bookmarks. Then go back to this chat and click on the bookmark.

cryonole

yes

firefox

DanielSank

Oh, ok, do what @ACuriousMind said.

cryonole

$\rho C dT/dt$

nope, still

DanielSank

18:32

You don't need to re-type it. When it works it will render all the math already here.

user54412

@DanielSank Debugging code :/

DanielSank

@ChrisWhite Fun timez.

@ChrisWhite Pro tip: write tests.

@cryonole do you have Chrome available?

cryonole

but anyways, so as to make the calculation 'complete' need to have a measure of uncertainty...

nope no chrome

DanielSank

@cryonole is this for a class?

cryonole

no

my dissertation

DanielSank

18:35

@cryonole can you post the raw data please?

As a picture here

user54412

@DanielSank Haha. I'm actually the primary test writer in the group. I made a regression test suite for everyone to use before committing. I also adopted a unit test framework, but discarded it because our code's structure makes unit testing far too difficult -- no one would ever write tests.

cryonole

DanielSank

@cryonole That's the raw data?

cryonole

yes

a picture of it

DanielSank

@cryonole does it fit to any particular model well?

cryonole

18:36

nope

this is just one of the trace

DanielSank

@ChrisWhite Too bad about other people not buying into tests.

Good on you for doing it!

Ok @cryonole here's what I would do:

compute the pairwise derivative, literally by doing something like data[1:] - data[0:-1].

^ That's numpy notation.

You get really noisy results as shown in my answer to your question.

Then I would average neighboring points together. Choose enough neighboring points so that the $\sqrt{N}$ factor helps you enough that you're satisfied.

cryonole

you mean do a running average of the derivative?

DanielSank

The spline might be better than this in the sense that it might give you better uncertainty with less smoothing. If you want to pursue that, then look up the formula for computing the spline parameters and use the kind of analysis shown in my answer to compute the uncertainties.

@cryonole Yes.

You can be intelligent about making the average window size different in different places.

For example, you obviously want to average on a less wide window near that kink at ~9ms.

cryonole

yes

DanielSank

Hey, by the way, how are you measuring temperature?

cryonole

18:41

cernox thermometers

user54412

@DanielSank What do you know about wavelets and sampling theorems on more topologically interesting domains than $\mathbb{R}$?

DanielSank

@ChrisWhite Nothing yet but damn that sounds right up my alley.

@ChrisWhite speaking of signal processing, I proposed a signal processing problem yesterday that a card-carrying Soviet era Russian theorist couldn't solve.

user54412

I ask because A novel sampling theorem on the rotation group showed up cross-listed to astro-ph yesterday. I also realized one of the authors is a Code Golf mod

DanielSank

@ChrisWhite I didn't even know this is an area of research. Cool!

user54412

Neither did I.

cryonole

18:45

you guys seem to be mathematicians to the core!

user54412

@DanielSank I'm curious what it could be. If a Soviet theorist can't solve it, it might not have a solution ;)

DanielSank

@ChrisWhite You want the long or short version?

@cryonole I'm an experimentalist.

Work with cryogenics, actually :D

cryonole

cool!

user54412

@DanielSank I'll take the long version if it's not too much trouble

cryonole

oh nice

DanielSank

18:46

@cryonole You mean cold!

@ChrisWhite I have a quantum two-level system, like a spin. Suppose it sits in zero magnetic field so there's no procession.

Then I add some noisy magnetic field so that the procession frequency is fluctuating.

Call this time dependent noisy frequency $\delta \omega(t)$.

I want to measure the spectral density of $\delta \omega(t)$.

@ChrisWhite with me so far?

user54412

yep

DanielSank

@ChrisWhite Cool. Suppose the system starts in $|0\rangle$.

I do a rotation pulse to put it into $|0\rangle + |1\rangle$.

(forget normalizations here)

user54412

I wouldn't have remembered them if you didn't say something :)

DanielSank

If I were to measure now I get 1/2 probability of either state.

However, suppose the fluctuating frequency comes in.

Now the system picks up an angle $\delta \phi = \delta \omega * \tau$ where $\tau$ is how long I let the system process.

@ChrisWhite with me?

user54412

this is bringing me back to the days of NMR lab in undergrad

DanielSank

18:52

@ChrisWhite Yes, very similar.

Ok, now suppose that after the noisy procession, I measure the system along the $Y$ axis. It turns out that when you do this, the probability to find the system (collapsed) in $|0\rangle$ is

$P = \frac{1}{2}(1 + \sin(\delta \phi))$.

Note that for $\delta \phi = 0$ the probability is 1/2, as we noted earlier.

@ChrisWhite still with me?

user54412

backing up a second, I think I'm missing why it's called $\delta \omega$ and not $\omega$

DanielSank

@ChrisWhite Oh, well, the idea is that without the noise the procession frequency is zero.

I call it $\delta \omega$ to remind myself that it's a noise.

user54412

ok

DanielSank

Could just as well call it $\omega$.

@ChrisWhite shall I go on?

user54412

just one more thing: how are axes set up?

user54412

18:57

you referenced y -- is that critical here?

DanielSank

@ChrisWhite Usual Bloch sphere construction.

@ChrisWhite Not if you trust me on the expression for that probability :-)

user54412

The probability looks like something I'd expect. And I'm a little rusty with conventions for these things. So z is traditionally the axis along the field?

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