The h Bar

user54412

4:20 AM

@KyleKanos I just randomly stumbled across this revision you were involved in

user54412

It made me chuckle a little, because as someone who's worked with PTF, PTF 11kly is "right" and SN 2011fe is unfamiliar to my ears

Kyle Kanos

@ChrisWhite No way, SN XXXXaa is the way to go

user54412

think of all the poor "unofficial" SNe these days that aren't blessed by an IAU telegram

Kyle Kanos

PTF just means it was discovered by one particular telescope which, in my opinion, is just a bad way to denote objects

Like HESS J1713.blah: tevcat.uchicago.edu/?mode=1;id=84

Also known as SNR G347.3-00.5

user54412

4:35 AM

to be fair, PTF consists of 3 telescopes at Palomar, and a dozen or so collaborators :P

user54412

but yeah, that is certainly a point

user54412

when will SNe be so numerous that we give up reasonable names altogether I wonder?

Kyle Kanos

I think that was the intent of the SN XXXXaa categorization

SN 2014 J was the Jth SN detected in 2014

SN 2011 fe was the fe'th SN detected in 2011

It makes perfect sense

user54412

well, if you discover millions per year (or whatever LSST claims), all names start to get cumbersome

user54412

then you start doing what galaxy surveys do and just use coordinates

user54412

4:39 AM

@KyleKanos lol. I remember being really confused for a time and thinking everyone was accidentally capitalizing the single letters.

Kyle Kanos

Most SNRs I'm familiar with use coordinates

Also, LSST is like 8 years from actually getting first light

user54412

so, I've been to PTF meetings where this was discussed -- what happens when you get into 4-letter territory?

Kyle Kanos

When you hit 3 letter territory, SN have officially become boring

user54412

like, what supernova is discovered right after SN 2023fucj?

Kyle Kanos

Or SN 2019 asr?

user54412

4:43 AM

Well I can confirm PTF 14ass actually exists. (Un?)fortunately it was a false detection (we log those with the same naming scheme).

Kyle Kanos

Well that's depressing that it was a false detection. Far more interesting to see the title choices for papers and talks on that

Dilaton

8:38 AM

@JamalS (and other) the homework-issue should NOT be misused to disallow all high-level (up to research-level) technical questions about advanced theoretical physics topics too :-(, such as this one for example (they should not even be tagged as hw!).

JamalS

@Dilaton: The new user had some misconceptions about the homework policy in general, and what homework means on this site. I was clearing that up, that's all.

Dilaton

Otherwise you will end up with on Physics SE it being no longer possible to ask questions about theoretical physics topics that are naturally technical in nature, such as CFT, TQFT, renormalisation, QFT etc for example. And concerning SUSY and ST only popular media channel level questions will be allowed to be asked. But this is what is already becoming true anyway it seems. Only few high-level technical theoretical questions are coming in these theys and the ones that still do get posted

JamalS

@Dilaton: I don't have a vendetta against these topics; these are my passions in physics, CFT, TQFT, etc.

Dilaton

are stigmated and mistreated by people who are neither interested in nor knowledgeable about theoretical physics as homework, which is insulting to enybody who wants to learn theoretical physics at a technical level.

@JamalS You have cast a closevote on that very high-level question. I remember you offered to be pinged about such nice theoretical topics in the corresponding meta thread. But this is all in vain, if the misisusing of the homework issue to drive away and disallowing high-level technical questions about this topics keeps going as it has since a few months :-(.

JamalS

@Dilaton: I haven't personally noticed this trend.

Dilaton

8:53 AM

This is why I stopped asking questions since more than a year as I still could. And now David Z has banned me (or he was at least the one writing the message) for linking to on-topic highly relevant information on PhysicsOverflow below some questions.

JamalS

@Dilaton: I think you should discuss any issues of this sort with the moderators, not in public chat.

Dilaton

This is equally crazy as it would be, if moderators on Math SE would ban people for liking to MathOverflow to say the least.

JamalS

12:29 PM

Does anyone have any experience with the xAct (xTensor) package for Mathematica? I'm having trouble using it.

David Z

1:01 PM

no, unfortunately

I mean, not me of course :-P

Oh, so, for general interest: NASA is trying to launch their Orion spacecraft at the moment - TV live stream

ACuriousMind

1:18 PM

@Dilaton Let me, as the one who cast the first close vote on that question, say that I feel insulted by your insinuation that the reason these questions are closed because "people who are not knowledgeable" "stigmatize" and "mistreat" them. The question just throws formulae at us and says "I don't know how to proceed". It doesn't tell us what dissatisfies the OP about the steps/derivations in other papers, and not even what the goal is, i.e. what we do want to derive. It's a bad question.

Dilaton

1:47 PM

@ACuriousMind Yes I am well aware, that you are among the few people who are knowledgeable about theoretical physics and related mathematics topics, so you should know better than shooting down the few still incoming high-level technical questions about such topics... I am seriously putt off by your attitude and leading role you take as an advanced TP student in disallowing theoretical physics questions at a technical (conversely to equation free, popular) level.

The recent issue has probably just driven away a potential new contributor of high-level content; well done to all who contributed to it.

JamalS

@Dilaton: The question was a bad question for the reasons ACuriousMind put forward; there was no context and no explanation of exactly what the OP was trying to do. He can't expect us to read the paper for him, and guess what confuses him. Whilst I don't think we've 'driven away a potential new contributor,' if we did, I wouldn't mind since he/she has thus far shown they aren't capable of posting a properly formulated question.

Kyle Kanos

2:26 PM

@Dilaton I wish you'd stop referring to field theories as "theoretical physics." They are not the only theoretical physics out there, as that term applies to all fields of physics in which theories are generated. Why not just call it what it is, rather than an (intentionally?) overly broad term?

Jim

Oh my, I seem to have joined chat this morning in the middle of an argument

Kyle Kanos

@Jim I joined in to see that as well. My comment's been brewing for some time now, finally got it out there

Jim

You've been wanting to ask Dilaton why he calls field theories "theoretical physics" for some time now? That's slightly an odd fixation

Kyle Kanos

What? No, I've been waiting to tell him to stop calling it by the overly broad term

ACuriousMind

I am struggling to find a theory that can't be reformulated as a field theory, though...

Kyle Kanos

2:36 PM

I suppose debatably you can say that fluid dynamics is a theory of fields

Jim

If you include astrophysics in physics, then I could show you a lot of theoretical physics that isn't what I'd call a field theory

Kyle Kanos

@Jim I try not propagating the myth that astronomy/astrophysics are distinct from physics.

ACuriousMind

@Jim It is physics, and I'm willing to believe that there are theories there that aren't field theories at all, because I know next to nothing about astrophysics

Jim

@KyleKanos I try not to propagate the myth that Astronomy is physics. Astronomy is almost as distinct as chemistry. But I'll admit that I think Astrophysics is more physics

keyword: almost

ACuriousMind

By as distinct as chemistry, you mean it's just applied physics, too? ;)

Obligatory xkcd

Kyle Kanos

2:42 PM

@Jim Maybe a few decades ago that might be true, but most astronomers I know still do some modeling

Jim

all sciences do modelling

that's why we get the yearly "girls of science" calendars

Kyle Kanos

On an unrelated note, I have no idea what I updated in python recently, but now my terminal is constantly spitting out 'import site' failed; use -v for traceback any time I open it (or refresh .bashrc).

ACuriousMind

@Jim ::groan::

Jim

Ahh terrible puns. Your ability to abruptly end a topic of conversation knows no bounds. :D

Kyle Kanos

Aha

I found it

I referenced two different site.py files in my PATH

Delete one and it works

Awesomesauce

David Z

2:55 PM

That's a weird error message for that condition

@ACuriousMind did you know the chat oneboxes XKCD?

Kyle Kanos

Yeah, it is weird.

David Z

On the other hand, physicists like to say physics is to math as sex is to masturbation.

ACuriousMind

@DavidZ No, but I should have guessed that :D

David Z

:-D

XKCD, Twitter, maybe Youtube? Also most things from SE sites. And some others. There's a list on Meta Stack Exchange

I think I have @Kyle beat for weirdest computer problem tonight:

Why I hate Monte Carlo integration: integrate f(x), 2 implementations agree. int f(x)/pi, same 2 impl, they don't agree. WTF?

Tweeted by ellipsix on December 4, 2014 at 1:49 PM

Kyle Kanos

I thought it could one-box any image file (jpg, png, etc)

David Z

2:58 PM

@KyleKanos yeah, that too

but for XKCD you don't have to give the URL of the image, just the URL to the comic page

Kyle Kanos

@DavidZ Hmm, wanna send me the files and I'll take my programming-fu and fix it?

(can't promise it won't return 0 for all integrals ;) )

David Z

that's an interesting definition of "fix" :-P

though in some cases 0 would represent an improvement from our current results

Anyway I think it oneboxes Github too...? Let's see:

github.com/diazona/SOLO/tree/…

nope

anyway that's the latest revision of the program I'm working on

Kyle Kanos

I think I found two errors already: (1) its C++ (2) it depends on GSL

:D

David Z

If you want to do it in Fortran, be my guest

Kyle Kanos

Looks like quite an undertaking

I don't know what it's even doing

And I'd hate to try 1:1ing it (better to understand what it's doing (and why) when translating it)

David Z

3:01 PM

hehe... sometimes, neither do I

It calculates integrals.

The best I can offer for a high-level description is my dissertation, unfortunately

I don't think the program would make much sense to anyone who's not in the field

Kyle Kanos

Actually, now thinking about the Github....someone who wrote a decent (yet convoluted) hydro code emailed me about my toy hydro model that I threw on there a few months ago

David Z

but unfortunately I can't really reduce this to a minimal working example. It integrates a product of 10 factors and if I remove any one of them, the results of two implementations agree

with all 10 factors, they differ by over 20%

@KyleKanos ooh cool! Always nice when your project gets attention

Kyle Kanos

@DavidZ Yeah...sad part is the project doesn't actually work

Jim

@DavidZ that problem is frustratingly inexplicable

Kyle Kanos

I'm getting negative energies when converting from conservative variables ($\rho,\,\rho\mathbf v,\,E$) to primitive variables ($\rho,\,\mathbf v,\, p$)

David Z

3:06 PM

@KyleKanos that's also weird

is it a numerics problem? roundoff error or something?

Kyle Kanos

Not sure yet what the error is

Probably I switched an index somewhere (e.g., used 2 when I meant 5)

David Z

that would make sense

but it's definitely something that wouldn't happen in an analytic evaluation?

Kyle Kanos

Correct, analytically it works

David Z

that's a start :-P

I guess from that point it's "just" a matter of standard debugging techniques, e.g. breaking down the calculation into components to see where the negativity comes from

Oh, random thing:

blogs.discovermagazine.com/neuroskeptic/2012/05/29/…

Kyle Kanos

I know duplicates come around regularly, but really:

-1

Q: How does the "World's simplest electric train" work?

You can find a video of it here https://www.youtube.com/watch?v=J9b0J29OzAU&list=UUuDG1RIJehn2kTPB95DPixA Question is, how does it work?

This same question about the same video was just asked a day ago

Jim

3:15 PM

and now it's gone

Kyle Kanos

Well at least my comment is visible to all of us currently active people in the room

David Z

it takes all kinds

Jim

3:30 PM

-3

Q: How will one calculate when you have calculate time dilation as low as for velocity 10 ms-1?

I just need mathematical technique because calculator cannot go so low

homework-and-exercises special-relativity

Another case of "Mr. TA, I can't do this homework because my calculator isn't powerful enough"

Kyle Kanos

A goofy notion

Like I said in my comment, my calculator handles it just fine

Jim

but something I've actually had a student say to me before

Kyle Kanos

I've never actually had anyone say that to me

Jim

I laughed at the student

F dot Floss

4:09 PM

Is there some clever way to get the data from a paper when it's in a massive table that can't be copied? I know sometimes they put the data in a "supplemental info" section on the journal website but assume they haven't here.

Physics Meta

0

Q: Is it appropriate to fix factual errors without the author's "permission"?

When browsing answers, occasionally you will find an answer a very good answer that has a factually incorrect statement in it. I have always operated under the philosophy that we want to stay true to the intent of an author's answer, but that it's unlikely they intended to be factually incorrect....

support editing

Kyle Kanos

@FdotFloss have you tried "email"?

F dot Floss

4:36 PM

@KyleKanos, how delightfully condescending. Have you considered that it's an older paper and they're long dead?

Unless you know of a beyond-the-grave email service, in which case please let me and probably most of modern science know

Kyle Kanos

@FdotFloss Oh, was I supposed to infer that the authors are dead from your negligence of mentioning anything about the paper?

If they are deceased and it can't be copied, the next best suggestion is "by hand"

F dot Floss

No, but you could've guessed that I might have thought of that, rather than being snarky

Kyle Kanos

No, I really would not have guessed that at all

Not that I assume everyone lives forever

@FdotFloss gilsmethod.com/quick-and-dirty-way-to-copy-protected-pdfs

First item on a Google search of copy data from table of uncopyable pdf

David Z

4:56 PM

Come on guys, that was unnecessary...

@FdotFloss what format is the paper in? I'm guessing PDF, but is it created from scanning images so that you can't copy the content?

In that case I think it has to be some form of OCR

or tell a grad student to do it, lol :-P

JamalS

6:47 PM

In case anyone was curious, see xact.es/documentation.html for help on xAct - I found the tutorial notebook by Joloyon Bloomfield to be the best.

nerdy

So, i'm messing up with this java app on the web about waves and i'm really curious about something. On the manual mode ( the others are "oscilate" and "pulse" ) , puting the damping to 0 , i'm realizing the action of simply lifting the left-end ( and then letting it stay fixed high, not returning it back ) and i'm noticing two different waves depending on the speed that i lift it. And also i'm noticing that they differ mostly in a parameter that seems like its size.

Whenever i lift it really quickly i think the "size" of the wave is really small and whenever i lift it slowly, the size of the wave is large .I'm really interested in what really is that size of those waves ( i know, they are not the usual periodic sinusoidal waves ) . Is it the wave-length ? I don't think so ... but then, if it is not, what is it ? ttp://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html ; this is the java animationIs it the wave-length ?

I don't think so ... but then, if it is not, what is it ? ttp://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html ; this is the java animation

Kyle Kanos

Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats. It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. Wavelength is commonly designated by the Greek letter lambda (λ). The concept can also be applied to periodic waves of non-sinusoidal shape. The term wavelength is also sometimes applied to modulated waves...

I don't really see a wave if I lift it straight up

nerdy

8:23 PM

Well, if we think of a wave as simply "traveling energy"

Then whenever we lift the left-end point , energy travels through the rope

So, we can consider it a wave ( i know that this is not usual pe riodic sinusoidal waves, but still ... )

Then i'm thinking what really represents that parameter (that varies with the velocity that i do the lifting ) that seems like the wave's size

Man, i'm sfor so many hours trying to solve this

so many days actually

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