The h Bar

@Phonon Right now, it's not more articulate than "What the hell was that about?" - but it seems to me he is essentially saying that we can compute non-perturbative amplitudes without ever actually doing anything that remotely resembles quantum physics in spacetime

It's intriguing, reducing physics to geometry

and it also seems like a somewhat natural progression from topological field theories and string theory amplitudes (the moduli spaces that the first guy asking a question mentions)

Phonon

@ACuriousMind ohh, I see, I can better imagine your feeling now.

yeah

did you know about his works before this vid?

ACuriousMind

@Phonon I vaguely knew that there was this dude with his amplituhedron, but I didn't really know anything about it.

Phonon

@ACuriousMind haha

ACuriousMind

1:24 AM

But...now it sounds like the kind of physics that I'd like to know more about

Guess I'll have to go read some papers soon :D

Phonon

well tbh yes, which was also why I shared it with you in the first place :D

and also considering you were a bit down with your studies

it may help intrigue your curiosity again ;D

ManishEarth

Who here watched Interstellar?

ACuriousMind

@Phonon Well, thank you :)

ManishEarth

The BH physics is mostly correct. They messed up on the rocket science though.

Phonon

@ACuriousMind np :D

ManishEarth

1:26 AM

Escape velocity. It's not rocket sci--- oh okay it is.

Phonon

@ManishEarth no not yet,

so there's a big flaw in the movie?

ACuriousMind

I'm not sure I really want to watch it...I like my Sci-Fi less Sci and more Fi :P

Phonon

kinda expected in every sci fi anyway, wouldnt you say? :D

or any movie for that matter :D

ManishEarth

@Phonon Well, they leave Earth with a 3 stage rocket, and then they leave a planet with 160% Earth's gravity with just the 3rd stage-module-thing. The planet was orbiting a large BH -- there have been explanations about the slingshotting necessary to leave that grav pull; however it's hard to explain escaping a planet with so less fuel

Phonon

@ManishEarth "orbiting a large BH..." wtf!

ManishEarth

1:33 AM

@Phonon Apparently gigantic with a large spin nullifying tidal forces

ShuklaSannidhya

5:02 AM

Is magnetic declination greater near the equator than at higher latitude or otherwise? (See Quito, New Delhi and New York). Its magnitude decreases from Quito(located close to equator) to New Delhi and increases as we go further north.

Is there any dependence of declination on the latitude ?

ShuklaSannidhya

5:16 AM

Or does the declination just changes randomly with latitude and there's no trend in its value?

^ here I am just referring to the magnitude.

David Z

6:17 AM

29

Q: Are expletives allowed in SE chat?

Along the lines of the discussion (poll) on expletives on SE sites, what is the policy for them in chat? In my mind, there is a very large difference between proper SE site content (posts and comments) and chat. Chat far more fluid than the "fixed content" of the site, and the occasional explet...

that being said, appropriateness is judged more by what you mean than by what you say

David Z

6:56 AM

1

Q: Integration involving Dirac Delta

I am trying find $\int_{all space} d^{3}q \delta^{3}(\vec{q})\frac{(\vec{p}\cdot\vec{q})^2}{q^{2}}$ where $\vec{p}$ is some fixed vector. Here is my solution, please comment. Let's align $q_{z}$ with $\vec{p}$, so we measure $\theta$ wrt $\vec{p}$. Since there is no $\phi$ dependence so I can...

homework-and-exercises integration distributions

I closed that somewhat instinctively but in light of the answers, maybe some discussion is warranted... the only thing approaching a question that I see is "Here is my solution, please comment", which is not really a question. Any thoughts from others?

Physics Meta

7:35 AM

0

Q: Does physics.SE help researches?

Do some concrete evidences exist that the physics.SE site offers any help with researches? (Note that researches on physics may not be confused with theoretical physics, that is a specific thing.) Were new works published there that later obtained recognition from the professional scientific comm...

discussion content-level

ACuriousMind

9:39 AM

@DavidZ I agree that the questionl, as it stands, isn't really a question, and that even if formulated as a question, it is likely to be just "I did this, where's my error?". Many people struggle with such delta functions though, and it is a rather typical things that comes up in physics...

Danu

10:34 AM

@ACuriousMind Wait, you hadn't heard of the Amplituhedron yet?!

Danu

10:50 AM

@Phonon your first video has an interested segment around the 43 minute mark, where they bring up the (then new) theory of inflation

Phonon

11:23 AM

@Danu yeah I know, did you get to watch the link to Nima's talk? me and acuriousmind gave it a shot, I fell off my chair after 10 mins and passed out, and acuriousmind was so puzzled afterwards don't think he's had any sleep since then ;DD

ACuriousMind

@Danu I was vaguely aware that there was something called that

@Phonon I had only four hours of sleep tonight, but that's unrelated :P

Phonon

@ACuriousMind xD almost!

Danu

11:44 AM

@Phonon I've already seen numerous talks by Nima on this topic

...and am similarly baffled. THis is slightly less surprising than @ACuriousMind's bafflement, since I do not really know much mathematics to begin with

I got interested in it when the papers originally came out

but yeah... flew right over mah head

Phonon

11:58 AM

@Danu yeah I see, cool that you knew bout his work. well I guess now you're kinda in the right path with your chosen program, I mean it's a start to make up for the seemingly lack of mathematical knowledge you think you may have. As for me, all the math I deal with in CMP is basically variational principles, functionals (for DFT), some group theory and that's kinda it,

Danu

@Phonon Yeah... some day... I'll be that smug bastard who points out people's handwaveyness

Phonon

@Danu btw, from now let's agree to call @ACuriousMind by Gauge for short, much simpler and pretty suited, what do you think? ;D

ACuriousMind

12:15 PM

@Phonon Heh. Do you know that that is also an actual, although rare, name?

Phonon

@ACuriousMind haha then there's no excuse not to! :D

@ACuriousMind in german it's also pronounced as "gage" in e.g. "engage"?

ACuriousMind

@Phonon It's no German name, it's English (I think)

And there, it is pronounced that same as the usual word

Phonon

@ACuriousMind ah kk

Qmechanic

1:09 PM

@DavidZ : After the edit, is the question more clear now? I guess there implicitly are two questions: 1. What is the integral? 2. Why does OP's method fail?

User Anonymous

1:45 PM

Hi guys. Just wondering if there is anybody around who's concerned with heavy-ion collisions etc. and can help me with this question of mine.

The complete Physics picture of these heavy-ion collisions remains unclear to me. Also, I can't find any book or review article where these are surveyed :(

@DavidZ - your profile says you work in high-energy physics. You have any leads regarding this?

David Z

@Qmechanic I still don't think so. Or to be more precise, the original reason I closed the question, namely that it doesn't appear to be actually asking anything, still seems valid to me.

@UserAnonymous let me see if I can think of something (but in the meantime I'll make some edits to your question)

User Anonymous

@DavidZ - Thanks. I'll greatly appreciate any leads whatsoever. :)

@DavidZ - Thanks for your edit, but doesn't a bulleted list list everything as items, whereas with arrows (->), I wanted to show a transition through all these stages? Anyways, you know what works on this site better than me, so it is OK. :)

Qmechanic

2:01 PM

@DavidZ : Edited the question some more.

Dilaton

2:23 PM

@Qmechanic it was wrong to unilaterally(!) close this question in the first place, and after the improvements it should really be reopend, so why dont you just do this?

David Z

2:37 PM

@UserAnonymous well, I guess that's mostly because I'm not a fan of ASCII-arrows except in fixed-width text. Feel free to change it back if you like.

@Qmechanic That edit does address my complaint about it not asking a question, so I'll reopen it.

But the question as a whole still kind of rubs me the wrong way. If you consider the two parts individually, they are (1) "what did I do wrong?" and (2) "show me how to do this", both of which are categories of homework-like questions that we routinely close as off-topic (with good reason IMO)

I think there must be some way to phrase the question such that it wouldn't bother me, though I can't think of it right now.

User Anonymous

3:01 PM

@DavidZ Not all. Thanks, and please do post if you come across any such resource. :)

BTW, what is so star-worthy about the two comments regarding editing some post which has been closed/reopened? I don't get it at all. Unless the starrer is the OP of that question :P

Oops. Minor typo in the preceding post. Read "Not all" as "Not at all". :(

David Z

No idea :-/ but you can't read too much into what people star

User Anonymous

Right :)

David Z

BTW you can edit previous chat messages by pressing the up arrow key, you know

User Anonymous

When I press up key, I reach my last message ("Right:)"), but not the ones above (on pressing repeatedly). So, I think, I couldn't have.

David Z

Weird, when I press the up arrow repeatedly it goes back to earlier messages

You have to make sure not to press any other keys in between, of course

User Anonymous

3:47 PM

@DavidZ Right now, when I press up, I can't even go to my last message. I guess it times out after a while or so.

David Z

Weird, it's not doing that for me. I guess it must be because I'm a moderator, but I didn't think that had an effect on the ability to edit chat messages.

User Anonymous

Hehe. This is funny, you are the moderator and you didn't know about this. :)

David Z

Yeah, it's not really our job to know all these things though ;-)

That's what Meta Stack Exchange is for

User Anonymous

I was checking the tags' questions, and it is weird that heavy-ion has only 8 questions in totality.

@DavidZ Yes. I was just kidding. :)

My message 1 contd. - Is it that this site has lesser users that care about those things/ work in that field?

David Z

I suppose so

Or at least fewer people who ask questions about it

Anyway I have to take off

(sorry)

User Anonymous

4:03 PM

Take off? Like a plane?

OK. No problem. Bye and thanks @DavidZ :)

Dilaton

5:30 PM

BTW @DavidZ unilaterally closing good technical questions AFTER Qmechanic (who is the most physics knowledgeable mod and probably did NOT think the question should be closed) has given a nice answer is implicitely a rather brutal violent act of overruling him. Generally, other very physics knowledgeable people may have good reasons to disagree with your opinion or about what rubs you the wrong way concerning technical questions. I generally wished Qmechanic s POV would be more respected

user3166976

5:59 PM

Hi

Hennes

7:03 PM

@dmckee There is. After quite a few previous glasses of the same. :)

User Anonymous

7:22 PM

5 hours past and still no answer to my resource recommendation question. :(

And only 16 views too. Really very :(

Psst - Around half of them would be mine only, so extremely :(

Hi @dmckee. Good to see another particle physicist (from your about me) in chat.

dmckee

Resource recommendation question tend to be slow. Especially when they are at once specialized and not famous.

Also, heavy-ion work is a not-very big specialty. As far as I know we don't have a expert on the subject among our regulars.

User Anonymous

Consoling words. You got anything to say about this question?

(Gosh I'm really acting desperate now)

dmckee

Not a thing. I'm in neutrinos and nucleon structure both of which are very far from heavy-ion territory.

User Anonymous

Nucleon structure? Using what?

dmckee

Electron beams. Jefferson lab.

In any case, don't despair just yet. There seem to be a number of physicists who check in every once in a while looking for things that are right up their alley.

They don't make the same impression on the site as the regulars, but I think there are more of them and when they do post it's usually good stuff.

User Anonymous

7:33 PM

JLab! Wow.

And yes, thanks for the comforting words. Are you talking about anna v?

Because she's the only other particle physics person whose profile I have stalked yet!

dmckee

I wasn't talking about anna specifically; I count her as a regular. She's retired now and I don't know that she every did heavy ions as such, though her interests are wide ranging so she might have the answer you're looking for.

User Anonymous

OK. Thanks. Yes, I'll wait patiently for some more hours/days.