The h Bar

ACuriousMind

17:00

You'd have to change his identification to make the title wrong.

0celo7

@ACuriousMind this mouse...I want to bear its children

where is @Huy

ACuriousMind

@0celo7 Uhhhh...what?

0celo7

I love my mouse!

ACuriousMind

Oh, your gaming mouse arrived?

0celo7

yeah

it looks like a damn spaceship, but I like it

NeuroFuzzy

17:01

@ACuriousMind Well it's not factually incorrect, I just like complaining.

ACuriousMind

Ah. So you're a troll ;P

0celo7

ACM has figured out SJWs

quite an upgrade

Secret

looks really cool

0celo7

I have copy + paste and forward and back in webpages on the mouse buttons!!!

dmckee

@ACuriousMind Nawh. It affects Fuzzy's oppression status and therefore the modifier to his offendedness attack.

ACuriousMind

17:07

@0celo7 You use HIM as a mousepad? :D

@dmckee I see. It seems I've missed some rule revisions for modifiers.

0celo7

@ACuriousMind I'm an engineer, I like my paperweights to have multiple purposes

oh GTA is so much better now

I can activate the special abilities on the mouse now

oh this is too cool

0

Q: Quantum Flavordynamics and messenger particles

My question is about messenger particles and how they relate to the concept of flavordynamics. I know that messenger particles travel between other particles to "communicate the force" like a photon traveling between charged particles to communicate the electromagnetic force. But how do messenger...

particle-physics

Danu

@NeuroFuzzy lol

0celo7

> Keep in mind that I'm only 14 so technical Jargon and equations probably won't make sense to me.

We need the most complicated answer ever

Danu

@ACuriousMind You have clearly not been exposed to enough gender studies

My mandatory course on "Identity in a global city" (or something like that) made sure to RAM that into me.

Secret

>Doesn't the weak force work within the neutron and not outside?"
Is he/she confused the strong force with the weak force?

and if my memory serves, neutrons can also participate in beta decay and exchange W and Z bosons?

David Z

17:19

@Danu oh, that's not really what I meant. My thoughts were like this: if it were a discussion on the main site, then yes, absolutely, it should be moved to chat. But on meta we tend to be more lenient about comment discussions. Between that, and the fact that Michael didn't really know how to use chat (he said), I wasn't as sure whether moving would be the right thing as I would be if it were on the main site.

It's not that I thought moving the comments was the wrong choice. I was just kind of ambivalent, and just hesitant to do it without careful consideration first.

Danu

@DavidZ Okay.

In any case, could you take a look at maybe restoring the first few comments?

Secret

$\text{>Keep in mind that I'm only 14 so technical Jargon and equations probably won't make sense to me}$

We need something akin to my diagrams on matrix multipication to do that, but I seriosuly doubt this will be easy given the maths in weak force is very messy involving a lot of group theory and lie algebra, and talking about visualising that, well at least I am not up to that task yet

and it will be more difficult if he/she is actually asking about the strong force, which is so messy that perturbation theory cannot be applied easily (I think...?)

(PS I don't know how to make quotes without accidentally quoting the next line on chat)

0celo7

> what?

it's easy

dmckee

@0celo7 Alas diracpaul quit the site. Otherwise we could have had 3D glasses diagrams.

Danu

@dmckee Wait, what? I'd love that! Damnit! Dirac, don't abandon us!

0celo7

17:29

why did he leave?

Secret

@danu yes, that's the problem I ran into, the quote line going through all my lines at once when I am just putting a ">" on the first line

Danu

I guess it's a matter of skipping to the next message

I think your messages are a bit long anyways, most of the time ;)

Secret

I have trouble finding good terms to simplify my messages, that's why I rely on latex and drawing diagrams a lot

I can say the same thing in a much shorter length probably because body language helps me to simplify the message

0celo7

@ACuriousMind 12,000 DPI is crazy

@Secret you're a strange fellow indeed

Secret

My chemsitry supoervisor had identified one stragne thing about me, such as how I read sentence compared to most people

dmckee

17:34

@Danu Here's one: physics.stackexchange.com/a/194688/520

I know there is a better one out their.

Secret

For most people given a sentence that describe a diagram as follows:

.Panal a blahblahblah, Panal b blahblahblah, Panal c blahblahblah

The read "panal a" and then they look at panal a of the diagram, after returning, they then start from the last fullstop to read to panal b, etc.

dmckee

@0celo7 He didn't tell us, but I guess frustration with the site rules.

Secret

for me, I can start right where I last left off, and not from the last fullstop

Danu

[Discography] Emancipator [3 albums]

►

Secret

@0celo7 That's why my supervisor said my sentences are lengthy

because it is a nonstop sequence of commas

Danu

17:36

@dmckee !! I think I have some 3D glasses

Secret

So in improving my research proposal, I have took account of that and started putting fullstops every now and then

dmckee

Another couple: physics.stackexchange.com/a/200611/520 physics.stackexchange.com/a/197239/520

And physics.stackexchange.com/a/198171/520

and so on. They are impressive diagrams, but like the level of math he often used overkill for the purposes they are put to.

One more: physics.stackexchange.com/a/192583/520

Danu

@dmckee Very neat

@dmckee Back in high school, I used to always get in trouble for being too loud/bored/annoying during the classes. I often had to stay after school until 5 PM, sitting in the classroom with nothing to do. My chemistry teacher used to spend those hours, spent in dead silence with just us two in the room, but putting on his 3D glasses and watching models of molecules on the internet. Maybe an early fan of (the late) diracpaul...

0celo7

@FenderLesPaul you're a bum

you've ruined all hope that I had for you

Danu

wtf?

0celo7

17:50

he knows what he did

Danu

Well, I don't.

FenderLesPaul

Really sorry dude I blazed a bit and put on some electric moon and totally went into a trance

and lost track of time

by the time I woke up it was like 9am

Danu

Lolwat

FenderLesPaul

wat

How was the football game though? Did that happen already?

Danu

You guys hang out IRL?

FenderLesPaul

17:53

oh no usually on Skype

we're too far away to hang out IRL

I think he's mad at me :(

@0celo7 I love you.

2

0celo7

@FenderLesPaul I'm leaving at 4:30

FenderLesPaul

Oh ok

0celo7

@FenderLesPaul yeah like a wifebeater loves his wife :'(

2

FenderLesPaul

@0celo7 youtube.com/watch?v=fm0T7_SGee4

sniff

Danu

Maybe you guys should keep these things to your Skype conversation? :P

2

I'm not sure of how much interest it is to the others here

FenderLesPaul

18:04

1

Q: Retarded Quantum Harmonic Oscillator

Suppose there is a harmonic oscillator and at some time acts on him a force. The external force $F (t)$ being zero before $t = 0$ and after $t = T$ . The oscillator was in its ground state for all time $t < 0$ until the force starts acting on it. Compute the dispersion ∆E of the energy at times $t >

quantum-mechanics harmonic-oscillator uncertainty-principle

the title of this post is offensive and politically incorrect

should be "differently abled" QHO

NeuroFuzzy

I'm terrible at differential geometry.

(step 1: acceptance)

0celo7

@Danu about as much as for your love life

battlelog.battlefield.com/bf4/servers/show/pc/…

@FenderLesPaul that's your kind of server

Huy

18:29

here I am @0celo7

Danu

@0celo7 I did ask, before starting to talk about that, if anyone was interested in hearing me out (the answer was yes).

So I don't think you're right.

Anyways, it seems we just can't get along today so let's just leave it at that.

FenderLesPaul

@0celo7 lmfao

@Danu we get along!

Danu

18:44

I think @0celo7 be mad

FenderLesPaul

@Danu indeed

I would agree

is that what football does to people?

Danu

@FenderLesPaul only in 'Murica ;)

(jk, everywhere, except what we call footbal is your soccer)

FenderLesPaul

Hehe

Danu

19:13

@DavidZ I'm going to be going to a bunch of "frequent" questions to scan all the comments for useless material, so expect a bunch of flags ;)

0celo7

@Huy the mouse is a lot bigger than I expected

I can't use the same grip as I did with my cheap dell

@Danu no

Danu

Good

@DavidZ Please give me some feedback: What do you think about flagging back-and-forth chains of comments such as here: physics.stackexchange.com/questions/2110/…

I think they're obsolete, but maybe you don't think they should be flagged; please let me know what your opinion is.

David Z

19:40

Anything that old is absolutely fair game for flagging IMO

Months is more than enough time for any useful material to be incorporated into a post

Danu

@DavidZ awesome

You will be buried in flags ;)

Why do I like doing this so much? :P

Hah @DavidZ you're deleting faster than I can flag ;)

David Z

It's easy :P

Danu

Damnit, trying to flag only to see "this comment has been deleted" once more!

Ah, that page is so clean now :)

David Z

For flagging I'd say prioritize the discussions - where the comments are long, and/or occur in large numbers. Obviously we can't actually delete all old comments.

Danu

@DavidZ YOU JUST WAIT :D

But yes, I agree.

0celo7

20:18

All you need is someone with comment OCD to do it for you

Danu

21:18

Oh internet, you're so great:

F. Galetto, "Riemann Hypothesis proved" (2014)

[abstract:] "We show a proof of the so-called Riemann Hypothesis. We prove the RH using the theory of 'inner product spaces' $I$ and $l^2$ Hilbert spaces, where is defined the 'functional' $(a,b)$, named scalar [or inner] product of the vectors $a$ and $b$. The proof is so simple that we suspect that there could be an error that we are unable to find."

NeuroFuzzy

woo!

Danu

@NeuroFuzzy Hairy ball theorem?

NeuroFuzzy

@Danu Huh? No, parallel transport.

Danu

@NeuroFuzzy It reminded me of a vector field that has a zero on top haha

skill patrol

22:03

And there's the kick-off @0celo7

skill patrol

22:23

@Danu I agree.

DanielSank

22:59

@Danu

I need you to do something for me.

Express some interesting information about physics.

Anything.

Danu

@DanielSank Anything?

Is this a trick question?

Something interesting that we understand because of physics, you mean?

Take your pick from GR stuff!

Alternatively I find it interesting how we can get away with QFT without bothering too much about fundamentals: Cross-sections all the way!

Also I am a bit confused atm, and you can probably help me: The trajectory of a vector field that starts at a point where the vector field is nonzero can never end up in a point where it is zero (try to trace it backwards to see why); but what is up with the charges in electromagnetism then? Is it just that the vector fields are not defined on the charges, or something like that?

@DanielSank Now what was this about?

ACuriousMind

@Danu $\frac{1}{r}$ doesn't look as if it is defined at $r=0$ to me :P

Danu

@ACuriousMind Yeah okay, so it's all just boundary conditions 'n' stuff

ACuriousMind

So the field generated by a point charge isn't defined at the position of the charge. Is this somehow surprising?

Danu

When things get confusing, believe in the boundary conditions

@ACuriousMind It started with me being confused about this statement about trajectories staying within the support of the vector field

I thought, somehow, that the physics stuff seemed like a counterexample

Then I came up with the tracing backwards argument

Then I realized the physics thing being a problem probably didn't make much sense, but wanted some confirmation

You know, how when you just get into uni they make you draw these vector fields with sinks and sources?

They seem like zeros of the vector field or something

...they're not, I guess

also wtf Daniel just disappeared again

I really want to know why he wanted me to give him some example

Danu

23:30

More dumb questions about vector fields:

In my notes we have the rotational vector field on $\mathbb{R}^2\cong\mathbb C$ "given by $X(z)=iz\in\mathbb C\cong T_z\mathbb C$"

I don't really feel super comfortable translating this to the usual vector notation

I want to say $X=i\partial_z$

But shouldn't I somehow first split off $|z|$? I have the feeling I should be identifying $z/|z|$ with $\partial_z$ instead, maybe

..so $X=i|z|\partial_z$?

wb Daniel

Slereah

and home

DanielSank

@Danu I need you to convey information to me through the internet.

Danu

@DanielSank I tried!

DanielSank

I need you to change my brain from not knowing a thing to knowing a thing.

Meeehhhhh, you pointed out some curiosities.

Danu

Dude, what are you on about

DanielSank

23:35

Just teach me something.

Danu

What are you looking for

DanielSank

Ok here, what's the deal with black holes? Do they suck things in and never let them out or not?

Danu

@DanielSank Unsettled question what exactly comes out in terms of Hawking radiation

...but something comes out

And it's due to purely QFT in curved spacetime effects

basically, it comes from the notion of particle being ill-defined in general spacetimes

DanielSank

@Danu Like I always say, asynchronous communication protocol.

@Danu Woah, weird.

Any experimental evidence?

Danu

@DanielSank But after making such a direct request it's a bit weird, but okay

@DanielSank No, but it's an inevitable consequence of QFT in curved spacetimes

DanielSank

23:37

@Danu Oh, interesting.

Thank you.

Now about your vector thing...

Danu

Basically, we're stuck with the non-vacuum "perspective" on a black hole so we see "particles" popping out with a thermal spectrum

Slereah

You don't even need to deal with particles

Danu

note the quotation marks

Slereah

Just do the solution of any field

DanielSank

@Danu When you talk about vector trajectories, do you just mean the integral curves?

Slereah

23:38

Around black holes, the vacuum splits

Danu

@DanielSank Yeah

Slereah

It turns into an inward flow of negative energy and an outward flow of positive energy

Danu

^I don't like that interpretation

DanielSank

@Danu The trajectory can have a limit at a point where the field is zero, yes?

Slereah

It's not an interpretation

It's what the equation gives you

Danu

23:39

^negative energy is

Slereah

It's not.

It's a common feature of QFT.

Danu

Cool story, but that's not true.

It's reducible to the interpretation of a single sign in an exponent

Slereah

If you check the stress energy tensor of those solutions it violates the NEC at some point

Danu

It's purely interpretation

DanielSank

@Slereah Yeah it is. You can look at equations one way and see energy flow, but from another perspective you can rewrite without any mention of energy.

It's just like the difference between particle and wave pictures.

Danu

23:40

@DanielSank A limit being what?

Slereah

NEC violation is independant of any interpretation

Danu

You agree that it can never leave the support of $X$, yes?

Slereah

It's also frame independant

Although it does depend of how you define the vacuum in your theory

Though IIRC all vacuum definitions engender NEC violations

DanielSank

@Danu Meaning that if I integrate the vector field and parametrize it then I have to put the parameter to $\infty$ to get to the null point.

This would be easier with an example field.

Danu

@DanielSank Sure

Not so interesting

I care about finite times

HDE 226868

23:42

In this set of lecture notes, the author writes that$$cP^0=\gamma mc^2=\frac{mc^2}{\sqrt{1-v^2/c^2}}=mc^2+\frac{1}{2}mv^2+\cdots\tag{1.41}$$Is this a Taylor series, and if so, why do we care besides taking the limit for low velocities?

Danu

@Slereah Who guarantees me that the NEC is even relevant at all?

@HDE226868 Yes

Slereah

@Danu : Relevant to what?

Danu

and nothing except low limit

DanielSank

@Danu Well, are you certain we can't get to a null point in finite time?

Probably need some smoothness condition for that to be true.

Slereah

The NEC is just an expression of the relation between energy and momentum

Danu

23:44

@Slereah Why should I attach any value to its violation (not to mention an interpretation)

HDE 226868

@Danu Thanks.

Danu

@DanielSank Trace it backwards

It can never leave

Slereah

Because the NEC is very relevant to a wide variety of GR theorems?

Including black hole ones?

Danu

once it gets there

DanielSank

@Danu Right I get that.

It's hard to do that mentally if I allow nonsmooth fields.

Danu

23:45

@Slereah Not convinced yet, but okay that's something, maybe

@DanielSank Doesn't matter; I care only about the smooth case

Slereah

I mean what other interpretation do you have for hawking radiation

DanielSank

@Danu Ok, I tried to get that out of you before :-)

Slereah

The whole virtual particle pair is kind of a pop science thing

Danu

My second question doesn't even make sense in the non-smooth case; vector fields fail to be derivations.

DanielSank

@Danu Fine whatever.

So what's the question?

Danu

23:46

@Slereah Correlation functions.

@DanielSank Second one; How do I translate that sentence

15 mins ago, by Danu

In my notes we have the rotational vector field on $\mathbb{R}^2\cong\mathbb C$ "given by $X(z)=iz\in\mathbb C\cong T_z\mathbb C$"

Slereah

@Danu : You get the stress energy tensor from correlation functions :p

Danu

Express $X$ in explicit "derivation" form

Slereah

They're the ones giving you the energy flow

Danu

(I already know the correct expression in "real coordinates", if you want help)

DanielSank

$iz = i ( x + iy) = ix - y$.

Danu

23:48

@DanielSank lol yeah... so

DanielSank

So, if you're taking the real part as the $\hat{x}$ component etc. then you get

Danu

No, I want $X=\text{something}\partial_z$

what is "something"

DanielSank

a vector field $-y \hat{x} + x\hat{y}$.

Danu

@DanielSank right

no, your correction is wrong

second correction is right

:D

DanielSank

@Danu :D

Danu

23:49

but can you do that?

DanielSank

@Danu What does $X$ mean

Danu

in terms of $\partial_z$?

DanielSank

?

Danu

the vector field

DanielSank

Oh

What does $\partial_z$ mean?

Danu

23:50

What I assume to be the single complex basis vector on $T_z\mathbb C$

DanielSank

(I think you're trying to recover the idea of Polya vectors)

Danu

lmao

oh god no

DanielSank

@Danu No really.

Danu

sigh... okay...

DanielSank

@Danu What is $T_z C$?

Danu

23:51

Why is it harder to express the v.f. in terms of $\partial_z$ than $\partial_x$ and $\partial_y$

@DanielSank Tangent space to $\mathbb C$ at $z$

Slereah

Tangent complex plane at z?

Danu

$\cong \mathbb C $ of course

hence $X(z)$ being given in terms of an element of $\mathbb C$ in the first place

but I want to translate it to the standard notation of elements of the tangent space

so... any progress? :P

DanielSank

@Danu I'm just confused. This is not related to previous question, right?

Danu

No

Well, it is, but only in the sense that it appears in my lecture notes :)

DanielSank

@Danu Ok, well, I have to figure out what the tangent space to $C$ looks like.

NeuroFuzzy

23:55

@Danu so what are you talking about? Wouldn't a tangent field be like $X=x_z \frac{\partial}{\partial z}+x_{\bar{z}} \frac{\partial}{\partial \bar{z}}$?

I'm sure you're way ahead of me, just curious :)

Danu

@NeuroFuzzy Is it?

If so then we're done

DanielSank

Ok have fun.

Danu

What is $x_z$?

NeuroFuzzy

a complex number

I have no idea, I've never read anything about complex manifolds before

I'm just guessing

I see no reason why not!

Danu

yeah but in this particular case, what is $X_z$ and what is $X_{\bar z}$

both $i$?

NeuroFuzzy

23:58

Hmmm??? So for my post I meant $x_z$ and $x_{\bar z}$ as arbitrary complex fields. If I saw $X_z$ I would guess it would be the basis vector $\frac{\partial}{\partial z}$.

Danu

You didn't look at my question, did you?

I have a vector field that's given by $X(z)=iz\in\mathbb C\cong T_z\mathbb C$

Now, this is in $\mathbb C$-notation

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