The h Bar

12:06 PM

One way to visualise a classical field is imagine a system with n degrees of freedom (well, because n degrees of freedom is easier to imagine than continuum many of it) and there are A LOT of particles, so many that when you try to track their evolution in time, everything just become a blur. Therefore we can approximate where these particles will be by the undulations of a field where darker regions means more particles are clustered there at some time t

How to imagine a single particle with continuum many degrees of freedom, I have no idea

perhaps, the vector that describes the particle's properties become so prohibitedly long that we gave up and describe it with a function instead

And now the fun part

The lagrangian, being the tangent bundle of the configuration space, seemed to tell us all the possible changes that can happen for a given point in spacetime

The action functional then, sum up all these dynamics along all possible paths between two given events

what happens if the vacuum is nonunique. Does that mean the vacuum is also participating in the scattering...?

The S matrix relates the in and out states in order to ensure the independence of the choice of basis. Therefore, as acuriousmind and many others said in the past, the S matrix play the role of transforming the incoming field along with the incoming states to the outgoing field with the outgoing states

Secret

12:44 PM

What I think happening in scattering: Two scalar fields, which can be treated as a superposition of continuum many modes in momentum space (what we called particles), interact. In the process, they exchange and combine or split the modes. In the end the resulting modes are the combination from the modes contributed by the two fields, which we saw as new particles

If this is the correct picture, then there is really a lot of stuff happening under the cover in particle experiments that we are not able to see directly

The picture also kinda justify the basic principle in string theory that every particle states are different modes of oscillations of strings, and one of the pants diagram illustrating how strings split and fuse. Pretty much mathematically the same thing is happening here in quantum fields except we call these modes particles and think they are some kind of point like object (I guess...?)

Ouch, we cannot even attempt to solve this numerically as the $V_{int}$ is not usually known clearly in a real setting.

Secret

1:11 PM

But wait, we are plugging two different infinities here, are you sure we can get away with this by plugging an unsigned infinity instead...?

And that, is time dependent perturbation theory

Secret

1:38 PM

And so, with the help of creation /annihilation operators, the scattering problem of 2 scalar fields is reduced to a problem of finding the transition amplitude of the vacuum state undergoing the interaction (factoring the free field theory along the way), that is the probability amplitude after the vacuum is sequentially transformed by the m+n quantum fields during the scattering process

Secret

Hmm, I am guessing we cannot use such formalism for scalar fields scattering within a CTC? I already forgot whether CTCs have well defined time ordering...

The question is then, how nontrivial it can be

Now googling: Time dependent vacuum, dynamic vacuum etc.

Pissed off layman

1:56 PM

Have you ever thought about writing a book :P

Secret

I cannot because I am still too dumb to write nearly 100% correct statements

Pissed off layman

Do you keep a diary?

Secret

Hmm, it seems the quantum vacuum is some kind of field lacking excited modes, which fluctuates due to the uncertainty principle and has a rich structure of sorts that governs everything we saw from particles to possibly daily life physics.

and no. I do kept a dream diary though

ACuriousMind

@Secret That first sentence is something one might read in a popscience book, but not a single part of it is true.

Pissed off layman

Truth doesn't make science popular :-)

Secret

2:05 PM

hmm ok, seems a sign I still don't fully understood the concept

ACuriousMind

"the quantum vacuum" is just the lowest-lying energy eigenstate of our theory. It's not a field, it does not "fluctuate" (values of operators can fluctuate, states cannot) and I have no idea what "rich structure" a single quantum state is supposed to possess.

Pissed off layman

Btw, Hawking is giving a talk about Penrose soon.

Secret

Well, by rich structure, This lecture note I am reading said the LSZ formula relates the scattering amplitude of 2 scalar fields with the vacuum expectation value of time ordered fields, thus the author said that the observations in particle experiments is related to the vacuum state and that the vacuum is nontrivial

anonymous

@Pissedofflayman Hawking can "talk" ? :O (When is it btw ?)

Secret

> You will note that we still have not calculated or evaluated anything, but merely rewritten
the expression for the scattering matrix elements. Nevertheless, the LSZ formula is of
tremendous importance and a central piece of QFT. It provides the link between fields in
the Lagrangian and the scattering amplitude S2
fi, which yields the cross section, measurable
in an experiment. Up to here no assumptions or approximations have been made, so this
connection between physics and formalism is rather tight. It also illustrates a profound

Pissed off layman

2:09 PM

@anonymous :D

anonymous

@Pissedofflayman I'm asking seriously.

I think it will be a pre-prepared speech given by someone else on his behalf

Pissed off layman

Stephen Hawking's @OxUniMaths Roger Penrose Public Lecture. 18 January, 5pm. Live podcast details.

anonymous

I will listen to it then. I love that guy :). Thanks for the details. But I am still wondering how he will give a speech by speaking only 2-3 words a minute.

@Pissedofflayman

ACuriousMind

@anonymous I'm pretty sure Hawking prepares longer conversations ahead of time

@Secret That's...weird phrasing. The vacuum has no "structure", it's just a state. But yes, given that state we can compute scattering amplitudes by LSZ, so it's "non-trivial". I suspect you're reading too much into the prose and too little into the formulae :P

anonymous

@ACuriousMind I see. It seems he types down the words and they are automatically converted to speech. (blog.swiftkey.com/…). And so I guess he will type everything down from before and run the text-to-sound converter during the podcast. (I have never heard his speech before so I might be speaking rubbish :P)

Secret

2:22 PM

Hmm I see. Now it wonders me whether I have interpret this formula correctly. In those notes by using creation and annihilation operators, the LSK formula for the 2 scattering scalar fields (where one has n modes in momentum space and the other has only 2) is given as follows:

I am guessing that reads: The interaction is given by the transition amplitude from the vacuum to some final state after the vacuum is acted by n+2 fields in sequence ordered by time, combined with the all the free klein gordon (something), and finally integrate all these contributions in some region of spacetime for each mode of the fields (particles(?))

ACuriousMind

Uh, by "reading into the formulae" I didn't mean that you should literally try to verbalize the formulae...

I meant that you should always check whether the phrases and interpretations in the text correlate to something in the formulae or if they are just flowery prose

E.g. while the vacuum appears in that formula, I do not see something like a "vacuum structure" in it.

Secret

Well, I might have thought in the wrong way as follows: Since QFT is relativistic quantum with continuum many degrees of freedom (hence we use fields), and field operators act on states like they do in quantum mechanics. If the vacuum state is some continuum version of the zero vector, then analogous to matrix multiplication, we should expect no matter what type of field act on it (I guess they are linear superpositions in QFT...?), it will not become anything other than a zero vector.
So I kinda think that statement makes sense in the sense that the vacuum state does not behave like a zero…

and thus a nonzero vector is a lot more nontrivial than a zero vector for example, hence the notion of "structure"

But I might be wrong, considering that the annhilation operator acting on the vacuum state gives zero (if I recall)

ACuriousMind

Why are you talking about the zero vector? The vacuum state is never the zero vector (the zero vector isn't even a state!), not even in non-rel QM!

Secret

...Probably drawn too much analogy of this with linear algebra, and thus forgeting that the zero vector is not a state

Pissed off layman

You seem to return to zero a lot :P

Secret

2:38 PM

because it is one of the easiest thing to make a math expression to not change by whatever tries to act on it

Anyway, how should I correctly read the physics of the LSZ formula, other than the final term is the vacuum expectation value of the time ordered fields. I seemed to often ran into the trouble of overinterpreting the physics in a physics formula..

Pissed off layman

That's why it's called the "identity element."

Pissed off layman

:-)

Secret

Pissed of layman: My issue when reading the meaning of formulae is that I tend to try to get physical meaning for every single math operator that appeared in a formula (in order to understand what is happening to the physical object that is expressed in the formula)

For example $q=\int_V\rho (x) dx$ makes sense because you are integrating all charge per unit volume and thus obviously you will get the charge in the end. Here everything from the integral to the integraton region to the integrand all have some operational or physical meaing

Pissed off layman

As far as the laws of mathematics are certain...

Secret

3:04 PM

Hmm, the amplitude blows up at the poles. I wonder what does it means for that meason who wandered too close to those spacetime points...?

Seeing some graphs here

user228700

@Help No, I didn't. I meant that you hijacked my position of "Asks questions for several hours" and like I said, I was only kidding.

Secret

loop contributions

ACuriousMind

@Secret Honestly, all those pictures are kind of distracting. Why are you posting them? They are not relevant to on-going conservation and you don't ask any specific questions about them.

user228700

@JohnR: Hello, again :-) I'm sorry for asking so many times, but for how much longer will u be around?

Secret

ok, I will stop posting them unless I have questions. I just found it kinda help me to organise my thoughts better

John Rennie

3:17 PM

@Kaumudi.H another one to two hours

user228700

@JohnRennie Oh. Bummer. Well, blame me for procrastinating before. Anyway, OK :-)

John Rennie

I am about to eat a very large vegetable pilau with chole, then around 17:00 UTC I will collapse into my armchair for a snooze to recover :-)

user228700

@JohnRennie OK :-) I hope your lunch is good! Ready-made?

John Rennie

I bought the chole ready made. The pilau I am making myself!

So at least the chole will taste good :-)

user228700

@JohnRennie :-P I see.

user228700

3:21 PM

Never had pilau before--only pulav.

John Rennie

Same thing? Stuff cooked with rice?

user228700

> "Pilaf is a dish in which rice is cooked in a seasoned broth."

user228700

Wait, Pilaf?

John Rennie

I think there's a lot of ambiguity in how to spell Indian foods in English.

user228700

No, pulav isn't made in broth.

John Rennie

3:22 PM

Ah yes, I think I've seen it spelled pilaf as well.

It's similar to the Italian risotto

user228700

Here, if you're interested:

user228700

food.ndtv.com/opinions/…

user228700

Oh, wtf.

user228700

Never mind, I don't like pulav anyway :-P (Although I suspect that it will taste very good with chole)

user228700

And wtf, pilau has veggies, isn't that right? Wow, it seems like I may be having a good influence on you :-P (JK)

user228700

3:27 PM

Gosh, I'm afraid people are going to start associating this place with "Oh, those two/three people talking about food" in the morning time now :-P

Secret

ok, it seems despite all those misconceptions and mistakes I have made in my thought process, QFT is a lot less scary than I thought (no, GR is WAAAYYYY scarier in terms of trying to make sense what goes where in those formulae, because I am so bad at tracking what those tensors are doing) (the notes I read onyl covers some scalar QFT, but a quick skim of another set of notes which covers much mroe does not have maths that are anymore scarier than that).

I am pretty sure with better training, I can tackle this subject

John Rennie

@Kaumudi.H Shrug :-)

user228700

@JohnRennie Goddammit, that looks absolutely delicious!

John Rennie

I have now started eating and I can confirm that it is delicious :-)

user228700

:-D Enjoy your lunch! I think I'm about to have a few dosas for dinner.

user228700

3:35 PM

@JohnRennie Carrots, peas and beans?

John Rennie

@Kaumudi.H yes, English veg

user228700

:-P OK. Those are good veggies. I might've added capsicum, some pepper and basil leaves as well :-P (

rob

We're going to have to rename the place "the h bar and grill" if the food discussions become any more prominent.

12

(UK version: "the h pub")

user228700

^ Do it x'D

ACuriousMind

I'll accept a rename only if you also come up with a physics pun for the "grill" part

I don't mind the food, but I do care about the puns.

Ramanujan

3:38 PM

@Kaumudi.H strange

user228700

@ACuriousMind @JohnR will come through and give us a spectacular pun, of this I am certain.

user228700

@Ramanujan Why?

Ramanujan

Dosas are eaten as fast food in morning ( I thought)

user228700

@Ramanujan Fast food? Well, they are typically breakfast food but we eat them at night--don't wanna have rice twice a day.

John Rennie

@ACuriousMind The h bar and rest(mass)aurant?

user228700

3:40 PM

@JohnRennie I believe in you and I know that you can do better!

Secret

So if I understood correctly, perturbation theory breaks down an interacting field into sums of all possible ways for the excited modes to propagate from the incoming fields to the outgoing fields, which by wick's theorem, can be expressed as propagators for the modes from pairs of spacetime points. We sum up all these contributions which are represented by feymann diagrams.
Any edges of the diagram that are internal corresponds to contributing modes of the interacting field that never left on the other end to be detected as particles, and thus we called these virtual particles

ACuriousMind

@JohnRennie arrrrrrrgh

user228700

@JohnR: Whenever you've got the time, please do come up with a bunch of puns and then we'll all vote! (Using stars?)

ACuriousMind

@Secret I'm afraid that doesn't make any sense to me.

John Rennie

It's a tough one, nothing good springs to mind

anonymous

3:43 PM

How about The h bar(beque) ?

3

rob

@JohnRennie But there's a lot of potential there ... perhaps a quadratic potential.

Secret

hmm ok, guess I still need to practice more...

Sir Cumference

All right, I think I've come up with a tagline

"What's new?"
"Neutrinos"

user228700

@SirCumference For what?

Sir Cumference

(because their symbol is nu)...

hwlau

3:44 PM

@JohnRennie you cook it yourself?

John Rennie

@hwlau the pilau yes, the chole no

rob

@SirCumference A flavorful suggestion

Secret

btw acuriousmind. How to interpret the physics in the LSZ reduction formula without end up overinterpreting and hence verbalised it like what I did previously. Is the vacuum expectation value of time ordered fields and the S matrix the only physically relevant thing in that formula?

user228700

@JohnR: What have we done to this place? :-P

rob

@Kaumudi.H It's cooked

3

Sir Cumference

3:45 PM

@Kaumudi.H It's turned into the snackbar

user228700

Oh God, the future looks dire...

John Rennie

Perhaps it's time to reveal I am actually a saboteur sent by the Social Sciences Stack Exchange

Sir Cumference

Jesus, everything is getting starred these days...

user228700

@JohnRennie The Social Sciences? .__.

anonymous

We have to share the physics chatroom with Seasoned Advice SE chatroom in the future :D @Kaumudi.H

user228700

3:47 PM

:-)

anonymous

The Frying Pan

Sometimes hot, always heavy. (cooking.stackexchange.com)

3

My gosh

They hardly talk about food

They should use our chatroom instead

2

And we should use theirs

:D

user228700

Yeah, they should learn from us.

rob

@anonymous They talk about physics?

anonymous

@rob Atleast they don't talk about "food". I scrolled up a few pages :D. See yourself :)

Sir Cumference

@anonymous I think we got our chats switched up

anonymous

3:50 PM

@SirCumference Yeah :P

rob

@anonymous I see: sledding, snoring cats, vacations, an urban legend, and Gigli

anonymous

@rob Hahaha XD

Sir Cumference

Darn, I'm so hungry ;-;

You guys keep talking about food

John Rennie

Buuuuuuuuuuuuuuuuuuuuurp!

anonymous

@JohnRennie Man, you eat fast :D

It not even 10 mins

:)

rob

3:56 PM

@ACuriousMind h barbecue =~ hbar, bottom quark

anonymous

@rob What does that mean ?

:P

Sir Cumference

ugh, my little cousin has my phone

anonymous

~ hbar

ACuriousMind

@SirCumference lol, what?

Sir Cumference

@ACuriousMind he was on physics chat

I thought I was hacked or something...

ACuriousMind

3:58 PM

@rob I...could get behind that

rob

Oh, there's the place where I can change the name. I'm not sure I was properly vetted before I got elected moderator.

ACuriousMind

Also, whoever flagged Sir's "what the fuck", lighten up a little, that wasn't an insult directed at anyone.

3

Sir Cumference

Sigh, someone flagged that?

Say, @JohnRennie, can I ask you an honest question?

ACuriousMind

@rob I'm pretty sure SE takes a "sink or swim" approach :P

@SirCumference No, only dishonest and duplicitious questions are allowed here.

6

John Rennie

@SirCumference Of course, though I may choose not to answer :-)

rob

4:02 PM

room topic changed to The h Bar(becue): General chat for Physics Stack Exchange (physics.stackexchange.com). For MathJax see meta.stackexchange.com/a/220976 (no tags)

7

Sir Cumference

@JohnRennie So, why didn't you apply to become a mod?

John Rennie

4

A: When should moderators close questions?

The fundamental rule of moderation is: Moderators can never win¹ If they don't close egregious homework questions the moment they are posted we moan and if they're over zealous about closing homework questions we moan. The best moderators can do is try not to lose too often, and I'd say the...

See the footnote :-)

anonymous

@rob Can we add something to the room's tagline also ? :D Like "General chat for Physics Stack Exchange and Foodies" ? :D

Sir Cumference

@JohnRennie You said with the exception of Math SE?

ACuriousMind

@SirCumference Read that there carefully, he's saying that moderation here is harder than anywhere but math.SE

(I disagree)

Sir Cumference

4:05 PM

@ACuriousMind Whoops

user228700

@JohnRennie Whoa.

John Rennie

@ACuriousMind you disagree?

I would have guessed the moderatorial time required per user was higher on the PSE than any other SE because we're stricter about what we allow.

ACuriousMind

@JohnRennie Yeah. I, for one, would not want to moderate something like parenting.SE where answers are often inherently somewhat opinions based and the topic is frequently emotionally charged for many people. I imagine that to be much more difficult than moderating a science SE.

Sir Cumference

Can someone superstar this so that people know why the chat's name is changed?

Loong

@anonymous You can also add tags to the room description, e.g. physics.stackexchange.com/questions/tagged/food

John Rennie

4:07 PM

@ACuriousMind Yes, good point.

ACuriousMind

@Loong ...we have a food tag?

TIL

Loong

food

Ramanujan

So many mods are here :P

Vishnu JK

@Loong LOLOL

Secret

$$\hbar b$$

Sir Cumference

4:10 PM

@Secret *$\hbar b q$

Secret

nah, the bottom quark is symbol b

Sir Cumference

Oh, that's what you were doing

Secret

or we can do this instead:

$$\hbar bbq$$

Sir Cumference

@Secret Meh, not obvious

anonymous

@Secret That is toooooooooooo much physics. :P Most won't understand what you mean :D

Secret

4:11 PM

A scattering event involving 3 quarks, two of them are botton quarks

also bbq is barbecue

(problem is, bottom quarks are too short lived to interact, or is that top quark?)

Sir Cumference

@anonymous I think a good 50% of people here are physicists/physics students

user228700

@SirCumference Sure, but I still don't know what that means.

Sir Cumference

@Kaumudi.H What what means?

anonymous

@SirCumference I'm sure all the physics students here won't understand it either.

user228700

@SirCumference What you guys are doing with the quarks thing.

Secret

4:13 PM

well, rob said that first, the barbeque is the bottom quark, see the star wall

Sir Cumference

@Kaumudi.H He's trying to write "the hbar BQ" in math

So $\hbar$ is hbar, and $b$ is bottom quark

user228700

@SirCumference Oh, OK, thanks.

Sir Cumference

I always wonder why SE's chat never had a PM button

rob

I'm all for puns with extra hidden meanings. But puns which are completely opaque unless you're "in the know" somehow aren't so enjoyable.

ACuriousMind

@SirCumference Because SE is not a social network.

Sir Cumference

4:17 PM

@ACuriousMind It doesn't need to be?

ACuriousMind

Within the SE model, there is no legitimate use case for ordinary users to send each other private massages.

Sir Cumference

A PM button in a chat isn't exclusive to social networks

anonymous

@SirCumference It has (indirectly). You can create a room for chatting with any user.

Sir Cumference

@anonymous Yeah, but it's public

HDE 226868

256

A: Any way to send a personal message to another user?

Nope. This has been suggested many, many times, going all the way back to the earliest days of the site. Prior to the creation of Meta SO, feature requests were posted on UserVoice: Messaging between users Declined without comment. User messaging or wall it's possible we might have so...

ACuriousMind

4:18 PM

@SirCumference True, but for what purpose do you want it?

Secret

One of the most frustrating thing when learning something new is that you thought you understood the topic, and then someone much more experienced said your understanding makes no sense to them, and you can only wonder why you cannot detect that error in the first place. And then rinse and repeat similar things many times

HDE 226868

1. It hides information; 2. Harassment.

Sir Cumference

@ACuriousMind I have no need for one right now, but it'd be nice to talk about site things or talk about matters personally

In my case I was hoping to share my code with someone, but tons of people kept flooding into the chat we created

ACuriousMind

@SirCumference Why does the SE chat need to provide that functionality?

anonymous

@SirCumference You can make a chat room view-only or read-only so that others don't drop in.

Sir Cumference

4:20 PM

@anonymous Dude, we didn't want other people stealing the code.

ACuriousMind

There's plenty of options to send private messages outside the SE network; if you want to communicate privately with another user, why insist on doing it through SE?

rob

@SirCumference Then SE is the wrong platform for you.

Sir Cumference

@ACuriousMind Convenience?

Secret

it also even more frustrating when people constantly detect new errors you have made again and again to the point they got really fed up with it, and you still wondering how on earth are those errors made and why it makes so much sense to you that you fail to detect they are nonsense

Sir Cumference

@rob Jesus...

Secret

4:21 PM

(above are my rant about me learning physics in general)

anonymous

@SirCumference Who on SE will steal codes ? :P Seems absurd.

Sir Cumference

@anonymous Programmers

ACuriousMind

@SirCumference Yeah, that's not enough in light of all the troubles installing such a system would bring. (high-rep users getting spammed with pleas for help, users harrassing others via massaging, etc.)

Sir Cumference

Some people will just take them as their own

rob

@SirCumference Not for you as a person. But as @ACuriousMind said better: private messaging isn't something that's supported here, and if you need it there are lots of other options available.

Secret

4:23 PM

Maths is slightly easier on that regard because if a concept makes no sense, plug it into the expression and nonsense that can be easily seen to be nonsense pops out, thus flagging an error in your thought process

Sir Cumference

@ACuriousMind @rob All right, if you guys insist

Secret

I really need a better way to improve my error thought process detection in physics

rob

@Secret I'm in the middle of reading Gödel, Escher, Bach, which is entirely about the error in this statement.

Ramanujan

@Secret in math we just do it :D

ACuriousMind

@SirCumference Well, I'm less "insisting" and more explaining why PMs aren't a thing on SE - you asked, after all!

Sir Cumference

4:25 PM

@ACuriousMind Yep, sorry, meant that

Ramanujan

@SirCumference if it's that important,just hack se for a day and do your work :P

(sorry if my words violates rules)

anonymous

Was SE ever hacked ?

Sir Cumference

@anonymous Hack exchange?

Ramanujan

@anonymous yes

Secret

One problem of my mind that is found by analysing my 6 years worth of dream log is it seemed to be a master of self delusion. Most of the time I cannot even detect I misunderstood something. This heavily annoys me and possibly those I ask them questions e.g. I already got question permabanned by a quantum professor when I tried to work out my misconception about entanglement a few months ago

anonymous

4:28 PM

@Ramanujan By whom? When ?

Ramanujan

50

Q: Has anyone ever hacked Stack Overflow?

While chatting with friends about hacking, a guy said that "if a site is getting popular/ or any competitive, it will somehow face severe hacks. Some used to expose it, others hide it". Out of curiosity I wanted to see if any such thing happened to Stack Overflow. Since Stack Exchange (being 5 ...

See 21 upvotes answer

anonymous

THIS IS COOL : stackexchange.com/about/security (HALL OF FAME). Wow SE wants to be hacked so that they can increase security. :D Good plan :P

Secret

It's as if I am born a crank but tries to learn right and not be a crank, but then my own mind deceives me to the point I cannot self check efficiently

(which is opposite to genuine cranks who think their beliefs have no problem and hence have no motivation to counter it)

This kinda brought me back to the discussion about The System between Barlerka and Kaumudi that other day:

while my peers think I am smart, some even think I can study for exams with little revision, I always insists myself to attend all lectures (and I did)

The primary reason for that (which is especially apparent for physics) is I rely on interacting with all those people around me to beat my self delusion so I can discover those errors

A self delusion is hard to deal with if you are not aware you are being self deluded

My case is I am aware being self deluded, but I have no idea how I am being self deluded. I don't think anything can get anymore self referential than that. I wish there's a formula that can calculate exactly how I am being self deluded

anonymous

@Secret You should write a personal blog :)

user228700

5:05 PM

@Sec: ^

anonymous

5:28 PM

@Maks holla !

Maks

@anonymous Hello !

anonymous

Learnt anything more about electron jumping ? :)

BTW see the new name of the room

:D

@Maks

Maks

Bar(becue) ? hahaha

Actually I got another question

I looked for it on internet, but I still have my doubts

about the particle-wave behavior or everything

anonymous

@Maks Ya ask

(I cannot guarantee that I will be able to answer your question though)

Hi @BernardoMeurer !

Bernardo Meurer

5:50 PM

What the hell

hbar becue?

ACuriousMind

@BernardoMeurer Just...follow the leads on the starboard to see the background

Bernardo Meurer

Ah

I get it

I knew this day would come

anonymous

@BernardoMeurer From now on its gonna be a chat room for physicists AND foodies OR both. :D

@BernardoMeurer IKR ;)

Bernardo Meurer

I want to burn all my money on useless things

anonymous

@BernardoMeurer Please burn it on me.

Bernardo Meurer

5:53 PM

You have uses

anonymous

I'm ready to act/become useless if you pay me :P

Bernardo Meurer

Also, can companies releasing new portable products please just use USB C

And not that micro B bullshit

Maks

@anonymous what is particle ?

Bernardo Meurer

@Maks Meaningless question

Maks

Cause when I looked for it, it said it was everything that had matter and occupied a place in space

@Bir

@BernardoMeurer why ?

Bernardo Meurer

6:02 PM

You might have a hard time proving a particle occupies "a" place in space

anonymous

@Maks In physics certain things are described by their properties and they don't have any correct "definition" as such.

ACuriousMind

@Maks The answer to that question depends on in which framework you want the answer. In classical mechanics and non-relativistic quantum mechanics, "particle" is a primitive notion that really doesn't have any underlying definition, in quantum field theory, particles are defined in terms of the field but the exact relation is difficult to put into a soundbite.

Bernardo Meurer

@Maks What ACM said

ACuriousMind

Start e.g. here for a discussion of what a "particle" is:

37

A: Do photons truly exist in a physical sense or are they just a useful concept like i = sqrt(-1)

There is lots of experimental evidence that the electromagnetic field exchanges energy with atoms in discrete chunks, and if we call these chunks photons then photons exist. Which is all very well, but my guess is that you’re really interested to know if the photon exists as a little ball of ligh...

Secret

6:26 PM

> In an interacting theory the field states are’t Fock states, and they aren’t even superpositions of Fock states. In fact right now we don’t know what the states of an interacting field are. The best we can do is calculate their properties using a perturbative approach or a lattice approximation.

ouch (that pretty much throw away any thoughts I have previously (scattered throughout the chat in the past hour) when I read that scalar field scattering lecture notes)

Sir Cumference

6:44 PM

I love the url

It just says "the-h-barbecue"

Maks

Why the h ?

planck constant ?

anonymous

@Maks h bar stands for the reduced plank's constant

dmckee

7:00 PM

For the visual you should note that h-bar is the symbol $\hbar$, and is given by $h/2\pi$.

(Use chatjax) if you can't see the math marked up.

Physics Meta

0

Q: Best of PSE 2016 - Best question

What was, in your opinion, the best question asked in 2016? Vote either by posting an answer linking to your favorite question, with a brief description of why it's your favorite, or by upvoting an existing post. Voting lasts two weeks, i.e. until Jan 29 2017. This is part of the Best-of PSE 20...

discussion

0

Q: Best of PSE 2016 - Q&A rookie of the year

Which user, who made their account in 2016, has added exceptional quality to the site in the form of questions and answers? Vote either by posting an answer linking to to a new user's profile and giving a brief description of why that user should win, or by upvoting an existing post. Voting last...

discussion

0

Q: Best of PSE 2016 - Less is more

What was the most impressively clear and concise answer in 2016? Note that a clear and concise to a very simple question is not necessarily particularly impressive. Vote either by posting an answer linking to a clear and concise answer and giving a brief description of why that answer should wi...

discussion

0

Q: Best of PSE 2016 - Most underrated answer

What was the most underrated answer in 2016? Underrated could mean that an answer recieved little attention/upvotes despite being of excellent quality. Vote either by posting an answer linking to an underrated answer and giving a brief description of why that answer should win, or by upvoting a...

discussion

0

Q: Best of PSE 2016 - Best self-answered post

What was the best self-answered post in 2016? Self-answered posts exist because the OP solved their own problem, or because they took the time to write up something useful/interesting for the benefit of the community. Vote either by making a post linking to a self-answered question and giving a...

discussion

Bernardo Meurer

@DanielSank Stop spamming

DanielSank

<3

I'll vote you worst new user.

When did the hbar become a bbq joint?

Bernardo Meurer

I'm not new :P

When we allowed John Rennie and Kaumadi a voice

DanielSank

ah

lol, someone is already downvoting the best-of posts.

Some people hate fun.

It's amazing.

user228700

7:14 PM

@Daniel: Ello! How do you feel about the name change?

user228700

@BernardoMeurer :-P Thanks (?)

DanielSank

@Kaumudi.H It's amusing.

My colleague had a plan to start a line of physics themed beers:

hbar: High quality, i.e. the bar against which other beers are measured.

Bernardo Meurer

@DanielSank I'd pay for that

DanielSank

Expectation value: Cheap and you get what you pay for.

user228700

@DanielSank Is this the same colleague who proposed the chappal museum?

Bernardo Meurer

7:16 PM

Actually according to my doctor I need to stop drinking

3

DanielSank

@Kaumudi.H no

Bernardo Meurer

I told my doctor she was basically telling the sun to stop shinning

3

DanielSank

Haha wow someone went and downvoted all of the best-of meta posts.

Good day to you too, Mr./Mrs. Grouch, whoever you are.

Bernardo Meurer

I'm going to go buy chicken, brb

DanielSank

@heather The "best-of" meta posts are up.

Physics Meta

7:24 PM

-2

Q: Best of PSE 2016 - Best community work

What was, in your opinion, the best answer in 2016 which where two or more authors contributed a significant fraction of the content? Vote either by posting an answer linking to your favorite community work, with a brief description of why it's your favorite, or by upvoting an existing post. Vot...

discussion

-2

Q: Best of PSE 2016 - Best answer directed at the layman

What was, in your opinion, the best layman answer in 2016? A layman answer is an answer directed at those without expert training in physics. Vote either by posting an answer linking to your favorite layman answer, with a brief description of why it's your favorite, or by upvoting an existing p...

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-2

Q: Best of PSE 2016 - Best baby-steps answer

What was, in your opinion, the best baby-steps answer in 2016? A baby-steps answer starts from simple principles and finishes with a complex and rich result. Vote either by posting a link to your favorite baby-steps answer, with a brief description of why it's your favorite, or by upvoting an e...

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-1

Q: Best of PSE 2016 - Never too old to learn

What was the best answer posted in 2016 by a user whose account was made in or before 2014? Vote either by posting a link to your favorite qualifying answer, with a brief description of why it's your favorite, or by upvoting an existing post. Voting lasts two weeks, i.e. until Jan 29 2017. This...

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-1

Q: Best of PSE 2016 - Best answer by a rookie

What was the best answer posted in 2016 by a user whose account was made in 2016? Vote either by posting a link to your favorite answer given by a rookie, with a brief description of why it's your favorite, or by upvoting an existing post. Voting lasts two weeks, i.e. until Jan 29 2017. This is...

discussion

HDE 226868

@DanielSank Stunning. I upvoted a few I thought deserved to be discussed, but you're still <0 on them all.

DanielSank

@HDE226868 meh, whatever