The h Bar

ACuriousMind

00:17

0

Q: Has the knowlege of rainbows gained from snell's law ever been used in a practical way?

So, I'm an AP physics 2 student at the moment, and I'm learning about Snell's law and refraction. Due to the changing speed of light (for these purposes; I am aware that C is constant) in water droplets and the stationary position of the observer, we know that the red portion of a rainbow will a...

^on-topic?

Stan Shunpike

00:35

I'm flagging as too broad

@ACuriousMind

dmckee

00:48

@TAbraham What room did you have in mind?

Mew

01:30

Only 9 more users are needed for the health proposal to kick off the ground:

191

Health

Proposed Q&A site for medical specialists, students, dietitians and anyone with health-related questions

Currently in commitment.

The proposal covers all aspects of health, from nutrition to disease

joshperry

01:48

Was there ever any research into the possibility that energy/mass is captured by space/time distortions instead of being the source?

Stan Shunpike

03:30

@bolbteppa thanks for the lecture notes. they are a great summary.

Stan Shunpike

03:53

Can I bounce some ideas about music around with someone? Anyone feel free to chime in.

This is partially related to configuration manifolds which is why I'm curious what people think.

I came up with this idea of a pace beat.

Basically, imagine a given note takes some time $t$ to occur. Then the length of the musical measure would be some positive integer $\alpha$ times the duration of the pace beat. That is, $\alpha t$.

So my basic idea is that I think musical measures are formed by multiplying the pace beats by rational numbers.

And in doing so you can get long notes and short notes by having them be perceived as longer or shorter than the pace beat.

Now, here's where configuration manifolds come in.

Given that I have now given a definition of note length, I feel it should be possible to formulate a discrete state space / configuration space model of musical sequences.

Whenever I compose, I am always trying to coordinate between 3 degrees of complexity. And these three levels set a kind of limitation on the number of possible configurations sequences can take on.

Anyways, I'll stop here because there's little point in continuing if no one reads this. If anyone responds, I'll say more.

David Z

06:16

@joshperry it's not clear to me what that would mean

@StanShunpike I considered not replying just because you said that :-P

I'm not sure I see the significance of what you're saying

Physics Meta

0

Q: I asked a non-homework question that was closed for being homework. How do I re-word it?

I asked a question "How to use the born rule to find..." and it was closed for being a homework-like question. Now this was not a homework question. It's also not the case that I am lazy. I own multiple QM texts and have read through them trying to figure out how to solve these kinds of problems....

discussion

Stan Shunpike

06:44

@DavidZ well, one of the problems I find when composing is that...a musical sequence doesn't just come together to form a song.

@DavidZ like I can make melodies all day. But to actually coordinate different parts, there are limits because the notes conflict.

The durations of the note affect the complexity. Usually the background / accompaniment has to have longer notes because the main melody has to have nothing else interfering with it or it won't be heard

So I usually write an accompaniment and then make the melody over top of that because, once the accompaniment is set, it makes it easier to find melodies consonant with it.

David Z

Yeah, that's pretty much how composition works.

Except for countermelodies and fugues

infinitesimal simplicio

Have you guys heard the harmony of the spheres?

Stan Shunpike

Nah, what's that?

infinitesimal simplicio

en.m.wikipedia.org/wiki/Musica_universalis

Stan Shunpike

Harmony of the Spheres sounds like a good name for a ballet

@DavidZ A lot of people say music is completely subjective, but I don't agree. There are some objective aspects. Like if it was totally subjective, then people wouldn't be able to write it and have other people like it.

David Z

07:00

Depends on how you define "subjective" I guess

Stan Shunpike

Omg speaking of which, I didn't realize how important defining stuff is.

Ever since we had that whole convo about distance, I've noticed how casualy I use definitions when talking to people.

It creates confusion.

David Z

Welcome to math ;-)

Stan Shunpike

Lolol its true but the funny thing is, I don't make that mistake when I write. But I realized I do it a lot when talking.

A lot of guys on physics chat have encouraged me to watch all the Susskind lectures in order

And I noticed he is very careful about getting people to clarify that sort of thing.

Oh, question: I noticed math SE doesn't have a thing to flag for off topic -- hw

Do they allow hw more than physics SE?

David Z

In practice, yeah.

Or at least they're not as strict about it as we are.

Stan Shunpike

Yeah, to be fair, they have a functioning overflow that permits professional discourse.

David Z

07:06

If you look at their meta you will see a lot of discussions about what to do about homework. I believe a while ago they had a large poll where the community voted to keep it on topic, presumably with certain restrictions.

@StanShunpike overflow?

Stan Shunpike

Like MO. Right? Like if people got sick of the quality of math being to low level, they could just choose to only participate in MO

David Z

Oh, yeah, I guess

Stan Shunpike

A lot of the hw questions I have noticed don't make much effort to show work. Is that your experience of it?

David Z

On Math you mean?

Stan Shunpike

Either.

I have seen them both on physics and math

David Z

07:10

Ah, well certainly there are a lot of HW questions that don't show work. Maybe not really a huge percentage of all questions, but too many IMO.

(at least here)

I have a vague sense that they are more common on Math but I really don't know.

Stan Shunpike

That Lie book thing you recommended was a nice change of pace from my other group theory books. I'm still trying to decide if I'm at that level or need something similar, but it is vastly more applicable to stuff I'm interested in.

I also never thought manifolds might be useful for music until I saw Mazzola mention them in Topos of Music. And Tymoczko uses orbifolds. But its not clear to me they actually advance our ability to make music. It seemed like math for show.

@bolbteppa it was weird seeing that Aristotle believed $F = mv$

Susskind talked about that a bit

David Z

08:04

@StanShunpike yeah probably, but that's not such a bad thing - most math is done for show at first.

infinitesimal simplicio

visualgo.net

David Z

08:58

I'll just leave this here:

@ellipsix well.. you need about 40kJ to cook a potato so you need a 40kW laser to cook it in 1s, i don’t have one :( http://www.theverge.com/2012/12/23/3794814/rheinmetall-50kw-laser-weapon

Tweeted by realscientists on March 24, 2015 at 8:55 AM in reply to ellipsix

David Z

09:59

So I guess we have a chat session in about 6 hours, if my clocks are not all out of whack?

Danu

11:04

@DavidZ We do?

@DavidZ I think "posing a challenge" (i.e. stating homework without effort) is a thing over there :P

David Z

@Danu maybe. Google Calendar tells me so but I might have the time zones mixed up.

Danu

@DavidZ Yes, yes, that's how that works ;)

@DavidZ Recently, I've been having a lot of problems with math not rendering on PSE, while I'd never experienced any trouble before. Did something change?

David Z

Not as far as I know

Danu

:(

David Z

well... there are MathJax updates from time to time. I think they're testing the latest on on Mathematics but I didn't think it was rolled out yet.

But perhaps it was.

For starters you don't have any script blockers or the like running, right? If so it'd help to test in safe mode (or use an entirely different browser, or a new profile)

Jan 30 is when the new MathJax was released, so if your problems started more recently than that, perhaps the new version is to blame

Physics Meta

13:15

0

Q: Sporadic MathJax failure

In the last couple of weeks, once in a while, MathJax has not rendered on my system (OS X). In both Chrome and Firefox I see the markup rather than the rendered equations. Is this a problem of my system, and if so is there a fix? Or does the problem reside elsewhere, outside of my control?

support mathjax

user54412

I think I was just serially upvoted. Never happened before. Kind of an honor, actually.

Danu

I think I only had a "serial" +30 once

infinitesimal simplicio

13:32

i had cereal this morning :D

ACuriousMind

@ChrisWhite Somebody likes you! ;)

ACuriousMind

Now that Engineering is in beta, should we perhaps link to it in the engineering close reason? (I know that we don't migrate to beta sites)

user54412

Variations of dose rate observed by MSL/RAD in transit to Mars

user54412

"we could estimate a crew taking a 360-day round trip to receive about 360 ± 180 mSv"

user54412

(compare to xkcd's radiation chart -- that's a nontrivial amount)

ACuriousMind

13:44

...we already knew that being is space is not that healthy radiation-wise, didn't we?

user54412

@ACuriousMind I did, you did, but all those people with dreams of arriving at Mars alive clearly did not

ACuriousMind

Well, 0.5 Sv/year don't immediately kill you. They perhaps make you wish they did, though...

user54412

arXiv or snarXiv: "The cosmological models called $\alpha$-attractors provide an excellent fit to the latest observational data. Their predictions $n_{s} = 1-2/N$ and $r = 12\alpha/N^{2}$ are very robust with respect to the modifications of the inflaton potential. An intriguing interpretation of $\alpha$-attractors is based on a geometric moduli space with a boundary:

user54412

a Poincare disk model of a hyperbolic geometry with the radius $\sqrt{3\alpha}$, beautifully represented by the Escher's picture Circle Limit IV. In such models, the amplitude of the gravitational waves is proportional to the square of the radius of the Poincare disk."

Jimnosperm

I can not understand how people are so terrible at punctuation.why do so many people not put a space after a period or a comma ? they have spaces between other words.and then,those same people sometimes put a space before and after a question mark or some other punctuation mark .it's so arbitrary.but seriously , where does this come from ?It's not like there is ever any time where a period that ends a sentence doesn't follow with a space.why are they so lazy ?

3

@ChrisWhite First one is snarxiv

ACuriousMind

13:55

@ChrisWhite snarXiv? Do you think this is snark or that it deserves snark?

user54412

arxiv.org/abs/1503.06785

Jimnosperm

@ACuriousMind snarxiv.org/vs-arxiv

user54412

Yes, more than half the figures in that paper are re-renderings of Escher paintings

ACuriousMind

@Jimnosperm If you ever find out, please tell me, I've been wondering about that for ages

@Jimnosperm Oh. There goes my afternoon :D

Jimnosperm

@ACuriousMind I've found that the less you know physics, the better you do

ACuriousMind

13:57

That is a bit unsettling

Jimnosperm

It's funny but I can't usually get 50%, which is what you'd get from random guessing

ACuriousMind

@Jimnosperm That is, you tend to favour random gibberish over actual stuff people write as science?

I repeat: That is a bit unsettling :D

Jimnosperm

@ACuriousMind Wait, you just said I favour random gibberish over random gibberish. That doesn't make sense

ACuriousMind

I kinda expected that retort. Well done.

Jimnosperm

Chin first, dude

are you reading the snarxiv abstracts or just playing the game?

ACuriousMind

14:06

I am a bit confused...the game only gives me the titles?

Jimnosperm

click snarXiv at the top and it takes you to the main snarxiv page

ADG

14:31

anyone of you know about newtonian mechanics?

ACuriousMind

I think it is safe to say that most people in this room know Newtonian mechanics.

ADG

if a person asked to prove that I is min about COM and someone answers why torque is min about COM, those both are not the same thing but the answer-er asserts it. @ACuriousMind

bolbteppa

@ACuriousMind
"We will however lift a number of other common assumptions, in particular the existence of a vacuum state, and the existence of theories on any Riemann surface (and not just on the plane). It would be interesting to investigate how this affects the set of possible models, and in particular the classification of minimal models. It is however mainly for the sake of generality and simplicity that we will lift these assumptions. We will indeed be studying not only rational, but also non-rational theories such as Liouville theory. Nonrational theories do not necessarily have a vacu…

ACuriousMind

@ADG What is the question here and what is I?

bolbteppa

I thought you told me I had to postulate the vacuum state?

ACuriousMind

14:40

@bolbteppa I honestly thought one had to

bolbteppa

It's crazy you can have theories with none!

ACuriousMind

Where is that quote from?

ADG

@ACuriousMind I is moment of inertia

bolbteppa

arxiv.org/abs/1406.4290 crazy notes

Chapter 4 has the affine symmetry stuff, creating $T$ from $J^2$ that I was asking about, but it's mental

ACuriousMind

@bolbteppa Sigh...more stuff to read :D

bolbteppa

14:42

I know

ACuriousMind

"bootstrap" mostly means that what follows will be crazy in some way :D

I've not yet really discerned what bootstrap even means

bolbteppa

Me too but I have to figure it out asap!

Jiminion

@ACuriousMind Bootstrap? It means to self-start, "pulling oneself up by their bootstraps"

ACuriousMind

@Jiminion I know the meaning of the ordinary English word, but it is also used as a technical term in string theory and QFT as an approach towards constructing them. It is probably meant to convey that we do not derive the theory from another, but build it from first principles, but I have not yet understood what exactly happens.

Jiminion

@ACuriousMind online.kitp.ucsb.edu/online/qft-c14/rychkov/pdf/…

ACuriousMind

14:55

@Jiminion Great, more stuff to read ;)

Terry Bollinger

15:11

Quiet in here today...

ACuriousMind

Hi @TerryBollinger! You're one hour early for chat session ;)

Jimnosperm

Shhhhh If you have to say something, do it quietly. You're breaking our concentration

@ACuriousMind Did you VTC this question?

Terry Bollinger

:)

One hour early?? It's 11:21 here, which is 21 minutes after the start of all the other chats I've attended... is there some kind of no-daylight-savings issue here?

ACuriousMind

@Jimnosperm Uh, yes? Do you think it is not effortless HW-like just because it is CFT instead of a Galilean transformation?

@TerryBollinger Probably. Chat session starts at the next full hour according to, well, chat

Jimnosperm

@ACuriousMind Effortless is not a reason to close as HW. I left a comment on the question. Can it convince you to reconsider?

In unrelated news, it's looking like people want me to stay as Jimnosperm. Really? nobody is interested in changing it up next month?

Terry Bollinger

15:26

Ah, yes, 4:00 PM UTC = 12:00 ET. Curse you Ben Franklin for that joke! Later...

ACuriousMind

@Jimnosperm Hm. I sort of see your point, but I cannot see how a question like "Why is a vector field a vector under rotation? I cannot see how this comes about" would not be closed as HW, because the answer is, as with all transformation behaviours - plug in the transformation and do the math!

In essence, I don't think "Why does this transform like this?" is a conceptual question at all, if "this" is defined in terms of things whose transformation behaviour is known.

Jimnosperm

The question is essentially that, but it could be that the OP can not see that it is so simple.

A conceptual explanation of the elephant in the room they are missing might be all the answer they need

ACuriousMind

I might also be a bit harsher than I am on other transformation questions in SR or classical mechanics because I cannot fathom how someone might have gotten to QFT/CFT without knowing how to see that.

Jimnosperm

Everyone has those moments where they can't see the forest for the trees

ACuriousMind

That is true. Note that I gave a hint in a comment and did not downvote the question

Jimnosperm

15:34

I think 5 votes to close may be slightly worse for a question in terms of getting an answer than 5 downvotes

PhotonicBoom

I'm thinking of posting an answer to this question

essentially what ACuriousMind commented i believe

ACuriousMind

@PhotonicBoom If you would also vote leave open in the review queue, then do it!

PhotonicBoom

Ok posting it now, feedback is welcome since I've never studied CFT before.

This could be totally wrong afaik :p

@ACuriousMind Can you access the review queue for a specific question or do you have to cycle through the others?

ACuriousMind

@PhotonicBoom I think you have to go through the queue normally. At 10k, you could go to the history tab and access any review that someone else has already done directly, but I don't think you can do that.

PhotonicBoom

Yeah I couldn't find a way. Its no biggie, I found the question anyway and voted to re-open. I also think this kind of problems can get quite confusing.

ACuriousMind

15:45

@PhotonicBoom It's not wrong, but be prepared for someone to ask how you knew that the measure transforms that way ;)

PhotonicBoom

hides

ACuriousMind

Oh, god, @Jimnosperm, arXiv vs. snarXiv is hard. Physicists suck at giving their papers good titles.

PhotonicBoom

Right I'm off, I got a thesis that needs doing unfortunately. See you guys in a bit

John Rennie

@PhotonicBoom You not hanging around for the Physics Chat?

Jimnosperm

@ACuriousMind And sometimes snarxiv produces good things like "An overview of evidence for dark matter"

ACuriousMind

15:51

@Jimnosperm It gave me The Wilsonian Effective Action. I would've sworn that is an actual paper, since it is an atual thing!

JamalS

@ACuriousMind Really? I got to 65% or so thus far.

Jimnosperm

Yeah sometimes it's crazy. I got as high as 70% but couldn't do better

ACuriousMind

@JamalS Nah, I'm consistently around 40%

JamalS

Some titles are grammatically or conceptually nonsensical.

ACuriousMind

Yes...and those are the actual titles, sometimes, at least when grammar is concerned.

Jimnosperm

15:53

the real paper I got once was "A bubble explanation of Einstein's dark matter"

WTF arXiv!?

ACuriousMind

Ceterum censeo Fabricam Super Saporis esse faciendam

...

Jimnosperm

that would obviously be real because snarXiv wouldn't make such an obvious mistake

ACuriousMind

I guess that one, because I thought: That's too absurd for snarXiv!

Jimnosperm

Inflation at the Edge of our Universe arXiv or snarXiv?

ACuriousMind

No way to tell, really. Probably arXiv if you found it worthwhile asking here ;P

Jimnosperm

15:59

I'll make it easier for you, the other choice was "LHC Prospects in Searches for Neutral Scalars in Pp Ogammagamma+jet: SM Higgs Boson, Radion, Sgoldstino"

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