The h Bar - 2014-02-22

« first day (1206 days earlier) ← previous day next day → last day (3715 days later) »

12:59 AM

@Amaterasu It is not the right view of bounty, it should just seem as a advertisement

@Amaterasu You should consider to write a short answer. It would be useful for someone come up in the future.

For the question of whether it is useful to someone, not only to physics.SE, you should consider the people get redirect to that question through search engine in the future, I mean in few years.

@Amaterasu It just means that there is not enough people with the same interest of you participe here. Even though the Earth Science is open, the same thing can happen and get closed. Many beta site follow the same path. There is no reason, just people don't want to participate

1:17 AM

the answer at this stage would be dv-ed

2 hours later…

3:29 AM

Thesis writing suuuuuuucks

I'm not very impressed with it either. But it means you're making progress no?

It does

But learning TikZ has been awesome

Yeah, TikZ rocks

I'm always amazed at what it can do

I've got 3 figures in my Numerical Methods section all done by it: the common discrete grid (showing x_i, x_{i+1}, x_{i-1}, x_{i-1/2}, x_{i+1/2} etc), the slope limiting, and my radiative loss curve

The latter of which is read off 2 files

I've almost given up on Inkscape, GIMP, Mathematica, etc. in favor of TikZ

It's pretty great

3:34 AM

I can't think of what my favorite TikZ figure I've made is

ChemFig is fun if you need to do that kind of thing, it's built on TikZ

I take that back, this might be my favorite:

pastebin.com/0vKFCaAN

Mostly because the fuel surface is random every time you make it, so it generates some cool things. But it also makes it annoying when your figure changes every time you recompile the paper...

Error: I do not know waht to do with the option "decorate"

:(

Sorry, put

\usetikzlibrary{positioning,decorations,decorations.pathmorphing,decorations.pathreplacing,patterns,
decorations.markings}

In the preamble

I didn't paste a MWE... shame on me

I was able to compile it with only decorations.pathmorphing and decorations.pathreplacing

253

Q: Nice scientific pictures show off

Task Show off your best scientific illustration ! The main purpose of this question is to share beautiful scientific pictures, preferably with an educational aspect. Content Your post must contain a nice picture and the associated code. One can post several pictures, but it must be done in...

diagrams 3d technical-drawing fun big-list

3

That might be of interest

Yeah, I have other figures that use the other decorations

Not all TikZ, but there are some nice examples there

(disclaimer: one is mine)

3:40 AM

Now it says I can't find the file 'pgflibrarytikzdecorations.code.tex'

Yeah, I've been watching that thread

@DavidZ I saw that one

@KyleKanos I can't help you with that one... compiles fine for me in linux and windows

@KyleKanos decorations itself isn't a library

Use just \usetikzlibrary{decorations.pathmorphing,decorations.pathreplacing}

@DavidZ Same error, now applied to pgflibrarytikzdecorations.pathmorphing.code.tex

3:42 AM

@tpg2114 huh, even with decorations in the library list? That's odd. It shouldn't. (unless you have a very old or very very very new version of TikZ, perhaps)

wait, maybe I take that back, I should check

ok never mind, it does exist

@DavidZ Using whatever comes with OpenSuSE and using TeXworks it's fine

@KyleKanos I was wrong. What TeX distribution and version do you have?

@DavidZ Tex 3.141592 and kpathsea version 3.5.6

I meant not the TeX version, but the distribution version.

Like TeX Live 20??

(for example)

I use whatever comes with Scientific Linux 6.4

3:46 AM

My figure it's cool enough to warrant a huge hassle to compile it I don't think...

@Kyle Run latex -version and look at the first line of output

$ latex -version
pdfTeX 3.1415926-2.5-1.40.14 (TeX Live 2013)
kpathsea version 6.1.1

that's my output

for example

Web2C 7.5.6

The full line is pdfTeX using libpoppler 3.141592-1.40.3-2.2 (Web2C 7.5.6)

pdfTeX using libpoppler 3.1415926-2.3-1.40.12 (TeX Live 2011)
kpathsea version 6.0.1

That's what mine says

Wow..my kapthsea version is way behind yours

Both of yours

And I'm on an OpenSuSE release 2 behind current... scientific linux must not update much

3:49 AM

@tpg2114 That's the whole RHEL model: don't update too much

Stability >>>> bleeding edge

@KyleKanos yeah, I don't know how Web2C versions relate to years, but that sounds pretty old

Oh, is there a copyright date in the output?

2k7

Maybe on the next line

@KyleKanos Which is why we dropped RHEL. Bleeding edge gave us the libraries and performance we needed, and we haven't had any stability issues

That's very old.

3:50 AM

@tpg2114 I haven't had any issues

@KyleKanos You just did ;)

@DavidZ It's only like 6 or 7 years

@tpg2114 Nonsense

Maybe your TikZ images could be even awesomer with modern decorations

@KyleKanos yeah, TikZ barely existed 6 years ago :-P

@DavidZ Oh

3:51 AM

sourceforge.net/projects/pgf/files/pgf

Version 1.18 was apparently current in 2007, and we're up to version 3 now

If you guys get bored writing stuff or making figures, en.akinator.com

I've only been able to stump it 2 times out of 10... with some pretty obscure things

SciLinux 6.0 came out in March 2011 and has had 4 updates in the 6 years

I think I've had 4 updates in the past 6 weeks

@tpg2114 I guess I should have used upgrades and not updates.

Actually probably way more than that... I don't update when I'm running simulations

3:53 AM

I get weekly updates or so

And apparently 6.5 came out 2 weeks ago.

Oh... Yeah, SuSE upgrades every 6 months

I might check that out after I graduate

Once you have something stable and working, it's best not to change them

Lest you brick a machine, or even worse everything works and you get different answers for the same simulations...

Been there many, many times

A lot of people install TeXLive manually, even if their Linux distribution already includes a TeX distribution, because it's really useful to stay close to the bleeding edge for LaTeX packages

I've bricked this laptop a few times

3:54 AM

tug.org/texlive

Something to think about

That's why I'm still running Windows 8

Well, 8.1, which I actually hate a lot when I was fine with Windows 8

8.1 messed up a lot of stuff that was just fine in 8

@DavidZ I put TeXLive and WinPython on a USB stick so I can use them anywhere in the world

It's really handy

Sounds nice

@tpg2114 Totally doesn't know his Tolkien

@KyleKanos Yeah, I know absolutely none of it. To the point I don't even see the missed reference...

And am now quite confused

Oh, that game thing

Did you go all the way out to 100 questions or whatever it is?

I'm at 42 but he's asking dumb questions

3:58 AM

I stumped him on a cyclist from the 70's and on that cheesy animated dog from Ghostbusters

He's asked me if Hurin (my choice, from Children of Hurin) had a son, a daughter, children, grandchildren

yes, yes, obviously, no

But he actually guessed Zhuul from Ghostbusters, so he was pretty close

And 3 times now he's asked if my character's been dead for more than 100 years

If you keep going and stump him, you can tell him what you were thinking so that way he learns it...

@tpg2114 No way

An AI developer made that thing

I will not support the Rise of the Machines

Wow it's late. I need to get home

4:01 AM

It's remarkably good at what it does. I actually spend more time thinking about the code it's using than trying to find characters it won't know

It just figured out Tycho Brahe in 12 questions, that's not bad

2^12 is 4096 people that can be uniquely identified with 12 questions... I think it's reasonable that Tycho Brahe is one of the 4096 most famous characters in history.

Possibly, although it's not just limited to famous people

"Your mistress", "your dog", and many other odd ones are possible answers

I'm a bit concerned though, one of the questions in the latest round was "Is your character an animated porn star?"

4 hours later…

7:57 AM

@DavidZ Useful things should be starred. It is hard to dig through the chat :)

3 hours later…

11:03 AM

0

Q: How do I go about reverting a Community edit?

What are the options I have, to revert a community edit? I don't want to simply edit my question; I was looking for something similar to a roll-back option where the approvers are notified that I wish to reject their proposed edits. I might be missing out on some obvious existing way to do it bu...

support suggested-edits

2 hours later…

Anonymous

1:03 PM

While this link may NOT answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. — Dimensio1n0 1 min ago

6:58 PM

Hello in Mark Davenports book visitors from time he talks of slowing time to go to the past and future. Does this sound like I'm understanding the theory right?

7:25 PM

@jinawee The edit seems valid. I think the improve button is the most appropriate in such situations where the added content is correct but the edit as a whole is not good.

@ChrisOkyen Sounds like a bunk theory to me, as traveling backwards in time isn't really physically possible

Davenport can get away with it by using vague language (some unknown machine to do this)

2 hours later…

9:20 PM

So how can you go tr Abel around a simgularity point come back to earth and be I the future I know the gravity slows time but does moving around a place of huge gravitational pull / density have any part of it ? Could u be still for. X time around he simgularity and then return to ear hand be the same place I. He cuture

The future

@ChrisOkyen I am not sure I follow entirely what you wrote there.

Ok so a simglRity can slow time riht due to the gravitational pull on time

Folloing

Following?

Perhaps not

I suppose by singularity you mean a black hole?

(Sorry, I stepped away from the computer)

Gravitational time dilation

Gravitational time dilation is an actual difference of elapsed time between two events as measured by observers differently situated from gravitational masses, in regions of different gravitational potential. The lower the gravitational potential (the closer the clock is to the source of gravitation), the more slowly time passes. Albert Einstein originally predicted this effect in his theory of relativity and it has since been confirmed by tests of general relativity. This has been demonstrated by noting that atomic clocks at differing altitudes (and thus different gravitational potential)...

Yes, being near a gravitational sink will decrease time as compared to someone not near the gravitational sink.

1 hour later…

10:48 PM

Where did we come down on this question?

15

Q: Are there simple ways to numerically solve the time-dependent Schödinger equation?

I would like to run some simple simulations of scattering of wavepackets off of simple potentials in one dimension. Are there simple ways to numerically solve the one-dimensional TDSE for a single particle? I know that, in general, trying to use naïve approaches to integrate partial differential...

quantum-mechanics schroedinger-equation computational-physics numerics

It seems like it's off topic for us, I think, but I don't remember there being much agreement

11:10 PM

@DavidZ I have mixed feelings about it. If it were a reference-request I might actually be more okay with it staying, but it's asking for answers to give the numerical method which makes me think it's off-topic

Although interesting and directly applicable to physicists. I would actually be okay with relaxing computational policies to allow numerical-method questions provided it's not implementation questions

So rather than "help me write the code" it's things like "how does X scheme work for this equation," kind of like we would for experimental physics "why does Ramen scattering allow us to see X"

But I do know that in the theoretical/experimental/computational physics world, computational things are third class citizens

Yeah... I guess that makes sense. I dunno. It's been sitting in the flag queue for a while, just on the cusp of having a consensus in favor of migration.

@tpg2114 this is true.

user54412

Another angle to consider, though: why step on the toes of the struggling SciComp site? There are a number of people there who really know their stuff, and these questions are decidedly on-topic for them.

@ChrisWhite For me, SciComp is more like "how do I increase efficiency," or "how do I parallelize this method"

Well, we shouldn't be thinking about whether it's on topic for them, only whether it's off topic for us. I think it is.

So I guess you're making the same point, but for a different reason.

Whatever, I think I'll go ahead and migrate it. Migrations are not so hard to reverse anyway.

I think by the policy, it is off-topic. But I don't like the policy really because I think that's a perfect example of a computational physics question that should be allowed here

user54412

11:15 PM

@DavidZ Well, I agree it is currently off-topic for us. I was more referencing the notion of changing the policy to allow some such questions.

Ah, OK. That's something to think about over the upcoming few days.

or weeks

We need to figure out homework first, that's far more pressing

yep

Since none of us computational people are up in arms over the computational-physics policy, it's probably okay.

user54412

@tpg2114 I think it's a great question (though when it comes to the Schroedinger equation, the answer is generall "no"), but two of the bullet points are stability and performance, which any non-physicist computational scientist can address, whereas most physicists couldn't

user54412

11:17 PM

That said, though, I don't really have a strong opinion on this

The solution to everything on SciComp is "Use petsc" which is annoying

@ChrisWhite Yeah, but physicists are more directly using the schemes and have experience with it. I mean, a mathematician can give me the textbook answer on stability for MacCormacks predictor-corrector method but actually using it for Navier-Stokes isn't so text book

Those are things that only people who really do it are going to know

user54412

@tpg2114 Very true. Honestly my thesis can be summed up as "figuring out the trivial details left out by mathematicians"

@ChrisWhite Yeah, and non-linear stability is way too hard to determine so it's always empirical. Which mathematicians tend to not like much

11:35 PM

So, in our GTR paper today, I spied the schwarzschild metric. I was all happy, and assumed the question to be a really interesting and awesome one. I left it for the last because I wanted to finish up the easy ones so I could relax and work on this one. Turns out all we had to do was calculate the length of a vector (the crux of the question was in knowing that what was asked for entailed calculating a length)

The course is awesome, but I keep having really high expectations for it :P

« first day (1206 days earlier) ← previous day next day → last day (3715 days later) »

Transcript for

Feb '1422

The h Bar

General chat for Physics SE (physics.stackexchange.com). For M...

join this room
about this room

00:00

06:00

12:00

18:00

all times are UTC

site design / logo © 2024 Stack Exchange Inc; legal

mobile