User talk:Maschen/Archive 8

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Figures

Hi, your might, or might not be interested in my proposal/plea? User_talk:Cjean42#More, please? to Cjean42. He is scarce on this site, but, if the spirit moved you to do this sort of thing... it could be helpful. Apologies if your past agility has spoiled me with expectations. Cuzkatzimhut (talk) 20:34, 13 February 2017 (UTC)

Sorry for more inactivity, I'll look into this and try and create with something, may take a couple of days... M∧Ŝc²ħεИ_τlk 17:05, 20 February 2017 (UTC)

Thanks, update is perfect. Linked it to a bevy of pages, as you may observe... Cuzkatzimhut (talk) 19:30, 21 February 2017 (UTC)

Nice to know it is useful, thanks for the kind feedback as always! M∧Ŝc²ħεИ_τlk 20:56, 21 February 2017 (UTC)

Me again; no, not greedy. Really, really low priority... for a rainy day... It struck me that Fig 7a or 7b, quadrilateral, or tetrahedron, on p 112 of M E Rose's Elementary theory of angular momentum, ( can you access this? ), might be really instructive for the article Racah W-coefficient. A picture is sometimes worth a thousand words... I could write the label, if desired... something like a=j1, b=j2, d=j3, c=j , f=j23, e=j12, or something more descriptive. Just a thought. Some people with a weak memory buffer like me are helped by geometric thinking... I am suprised I could not find something of the sort in Wikimedia, but maybe I can't search right... Cuzkatzimhut (talk) 16:35, 13 March 2017 (UTC)

Hi, sorry for delay, yes I can access the book (just about, some pages do not show up, but 112 does). I'll reproduce the figure a.s.a.p M∧Ŝc²ħεИ_τlk 13:13, 17 March 2017 (UTC)

Angular momenta in the Racah W coefficients. The top is a 2d plane projection as a quadrilateral, the bottom is a 3d tetrahedral arrangement.

No, you are not greedy, I have hopelessly fallen out of WP routine... Here it is, if you would like to split the image into two or just use one or the other (quad or tetrahedron), let me know. M∧Ŝc²ħεИ_τlk 13:36, 17 March 2017 (UTC)

Wow! Thanks again, on behalf of WP readers... Cuzkatzimhut (talk) 14:06, 17 March 2017 (UTC)

You're very welcome!

All the references you have shown (Whitham's linear/nonlinear waves, Lee's particle physics, now Rose's angular momentum) look brilliant! (YohanN7 often provides excellent refs also). Will read into them more... M∧Ŝc²ħεИ_τlk 17:33, 17 March 2017 (UTC)

Figure request

Hi... it's been a long time! I still don't know how to make 3D pictures with software. If you had the time, could you try something for me? I would like several images based on this diagram. Ideally

• one would just be a cleaned up rendition of what you see
• one would colorize the cube with the label $\mathbb {H}$ in the same color.
• one would colorize the plane through the middle of the cube with the label $\mathbb {R} ^{3}$ in the same color.
• one would colorize the upper hemisphere with the label $SO(3)$ in the same color.
• one would colorize the circular intersection of the hemisphere with the plane with the label $S^{2}$ in the same color.
• one would present all the labels at once with different colors and appropriate translucency, (except for the cube perhaps, which would remain transparent and use a black label.)

What do you think? Might you be able to do this favor for me, even if it is just the last item on the list? It's a diagram for a talk I'm giving to nonmathematicians. Maybe you can even spot inaccuracies in it, but I feel like it will do a good job. Please let me know what might be possible: thank you Rschwieb (talk) 20:09, 22 March 2017 (UTC)

So sorry for late reply, I'll try an SVG version now. Hope it's not too late for your talk... M∧Ŝc²ħεИ_τlk 08:38, 25 March 2017 (UTC)

Here, let me know of improvements/corrections. M∧Ŝc²ħεИ_τlk 09:50, 25 March 2017 (UTC)

Wow, that looks great! I wasn't sufficiently clear about the circle, though. The region that represents $S^{2}$ is actually just the perimeter of the circle and not the whole disc. If you could light up that circle in orange and move the label arrow to point at it, then I think we're good! Rschwieb (talk) 11:11, 25 March 2017 (UTC)

Sure, sorry, fixed now. If R³ is shown as a plane, I should have realized that S² is the circle without interior, since the interior would be the volume of a 3d sphere.

Out of interest what is the figure exactly for? Seems like quaternions and their connection to SO(3), in a lower dimension. M∧Ŝc²ħεИ_τlk 12:07, 25 March 2017 (UTC)

This is awesome! To answer your question, I'm trying to provide a visual aid for my fellow employees (roboticists and software engineers) who might not know how to visualize quaternions and their relationship to 3-dimensional geometry. I want to relate the picture to the ones that can be drawn for 1- and 2- dimensional geometry (which I'm requesting below too.)

The aim is to illustrate what quaternions are the model of 3-space, which ones are doing the transformation, and finally to convey that there are a lot of other quaternions we just don't have to think about when using them for geometry.

You're right: everything in this beautiful diagram you've drawn is "compressed" by a dimension so as not to blow the viewers' minds :) I feel like I might have seen this picture somewhere before, but I couldn't dig it up, and besides that it was probably in black and white in a book.

I will be sure to send you a copy of the presentation (there shouldn't be anything proprietary at all, so that should be fine.)

I feel bad for followup requests, but I really hope they are pretty simple to do:

• First, can you add the point that is the center of the sphere?
• Secondly, two other diagrams:
  • A line with 0 and 1 marked, and labeled $\mathbb {R} =\mathbb {R} ^{1}$, and a label of $SO(1)$ for the point 1.
  • A plane labeled $\mathbb {C} =\mathbb {R} ^{2}$ and a circle with center marked, and a label on the circle $SO(2)$.

I'm purposefully omitting labels for $S^{0}$ and $S^{1}$ in these two diagrams. They aren't really as relevant as $S^{2}$ is in the third diagram. 14:36, 27 March 2017‎ Rschwieb (talk)

That's interesting, had a feeling it was to do with quaternions. As mentioned before, I hope I am not too late creating them.

Please don't worry about the follow up requests! I'll try and get them done this evening.

BTW I added your signature, it wasn't signed. M∧Ŝc²ħεИ_τlk 12:36, 28 March 2017 (UTC)

Had a chance to get them done now. Feedback is welcome. For the SO(2) case are you sure you didn't mean the interior of the circle to be coloured in and labelled SO(2), while the boundary would be S¹? M∧Ŝc²ħεИ_τlk 13:17, 28 March 2017 (UTC)

Also for the SO(1) case, are you sure the interval 0 < x < 1 for real x is not to be a coloured line segment labelled SO(1), while the end points (would be) labelled as S⁰? I can re-colour things to match the original diagram. M∧Ŝc²ħεИ_τlk 16:42, 28 March 2017 (UTC)

No, you are not too late: the talk is in mid April, and I wanted to be sure not to be begging you at the last minute. These are all great!

For both $SO(1)$ and $SO(2)$ I'm pretty sure I mean just the surface of the discs and not the interiors. In the complex plane, it's just the items on the perimeter of the disc which produce rotations (things on the interior rotate and make the plane contract.) Same for the real line: the only orthogonal transformation that preserves the orientation of the line is the identity transformation (-1 produces a reflection.)

In the 3-d diagram I requested, I am also only talking about the surface of that hemisphere :) I can't think of a good way to emphasize that, nor do I think it is very important given that I can clear it up verbally. Rschwieb (talk) 16:02, 2 April 2017 (UTC)

OK, no worries, glad you like them! ^_^ M∧Ŝc²ħεИ_τlk 08:07, 3 April 2017 (UTC)

Could you convert the svg of the line into a png? I seem to be having trouble getting it to play nicely with my beamer slides. Rschwieb (talk) 21:55, 3 April 2017 (UTC)

Sure, they are all converted to png for completeness.

If it helps, when you left click on the image once, it should be possible to right click and save the image as a png. (Using Windows 8). M∧Ŝc²ħεИ_τlk 11:14, 4 April 2017 (UTC)

Which software do you use M? I tried to learn one tool once and decided it would be quicker to code up my own SVG tool in C++ than to understand someone else's. Yes, I am sick. I made my own math library (removing all dependence on msvcrt.dll in Windows OS), matrices with operations on them including power series like exp, rational numbers, complex numbers, quaternions, etc, templetized abstract and concrete classes for mathematical structures, Lie algebra thingies and all sorts of weird stuff. It could spit out Tex. Client applications using this library were extremely quick (and short) to code up. This all resides on a crashed hard drive. I miss it. But that would take too long time too, so I dropped it. YohanN7 (talk) 11:48, 4 April 2017 (UTC)

I really appreciate all your extra effort. I'm working on a linux machine now, actually, and there's probably a way to save as png but I was having trouble finding it :) Rschwieb (talk) 12:35, 4 April 2017 (UTC)

Do you have any recommendations on software to use to create SVG graphics? I'm getting exceedingly irritated with Inkscape, because of rendering issues. I've been converting everything to PNG before uploading to Commons. Stigmatella aurantiaca (talk) 12:33, 4 April 2017 (UTC)

Hi all! ^_^ For all diagrams, I use Serif DrawPlus X4, sometimes X6. Serif is easy to use (interface is easy to get used to, nodes on shapes easy to edit) and generally very reliable (doesn't crash (often)). You can readily export files to svg, png, jpeg, pdf, and others. X6 is very similar to X4, interface has changed slightly, but seems to have a few bugs compared to X4 e.g. arrows not exporting properly, some slightly faulty "quickshapes" (pre-made shapes like polygons, clocks, grids, faces, etc. which can be drawn to size, then edited). These bugs may just be the version I have. Anyway X4 is strongly recommended. (Never used X5, or later versions after X6).

Never liked Inkscape or GIMP, always found them prone to crashing, slow, lots of clicking, awkward interface. I haven't used either for a long time, maybe things have improved. Can't get into CorelDRAW, interface always seemed too much.

There is also Xara Photo & Graphic Designer, looks like a great alternative. Last year I tried a free version since I have basically outgrown Serif. May buy it sometime... M∧Ŝc²ħεИ_τlk 17:02, 4 April 2017 (UTC)

Thanks much! Stigmatella aurantiaca (talk) 17:09, 4 April 2017 (UTC)

Question about File:Relativistic gravity field (physics).svg

Current image, not the same as the one which had sparked this talk discussion.

I wanted to use this figure, but just noticed something peculiar a few minutes ago. In the left image, the lines diverge rather than looking as if they will tend towards parallel (flat space) at infinite distance. Stigmatella aurantiaca (talk) 03:28, 2 July 2017 (UTC)

It is a crude illustration of the trampoline analogy, will make it clearer. M∧Ŝc²ħεИ_τlk 06:45, 2 July 2017 (UTC)

Tweaked, any better? M∧Ŝc²ħεИ_τlk 07:16, 2 July 2017 (UTC)

Actually, no. Here is where I was intending to use it. At infinite distance, the coordinate grid lines should be equally spaced. Viewed from above, one can observe the spatial curvature induced by mass-energy. Viewed from an angle, one sees both the curvature in space and the curvature in time. The problem with the angle view, is that one cannot tell the difference between a "curvature in time only" theory versus a "curvature in space AND time" theory.

Rewriting the Spacetime article has been a bit of a long term project for me. On March 15, it looked like this, and some Talk page commentators called it one of the worst articles in Wikipedia. Since then, I have written sections 1, 2, 3, 4, and 9. I threw out irrelevant cruft and deleted a few outright falsehoods from the other sections, while otherwise not touching those old sections except to move them towards the end so that they are out of the way.

The intent in 1:Introduction and 4:Introduction to curved spacetime is to keep the technical level down to where an intelligent middle-to-high-school student can read them. Every major subsection in sections 1 through 4 is linked to a summary in 9:Section summaries.

user:Greg L, a technical writer, has been working on the lede.

My latest revisions involved throwing out a section on Rindler space that took me several days to write but which never really worked, and including a new section on Sources of spacetime curvature, which, as I've told several people including an outside reviewer, was inspired by your beautiful File:StressEnergyTensor contravariant.svg.

I've drawn 29 illustrations for this article. None of them match the quality that someone like you can bring it, but I do have a few favorites, including this one on Terrell rotation.

Stigmatella aurantiaca (talk) 10:54, 2 July 2017 (UTC)

Ack, yes, sorry. For now would you be able to make do with the existing png (File:Gravitation space source.png)? I'll try to create an svg version of it this evening if that's what people want. M∧Ŝc²ħεИ_τlk 05:36, 3 July 2017 (UTC)

All of the currently available gravitational spacetime graphs appear to be bitmaps, so yes, an SVG would be appreciated! Thanks, but don't let this ruin your 4th of July (assuming that you live in the US)! Stigmatella aurantiaca (talk) 20:41, 3 July 2017 (UTC)

Sorry for delay, I traced over the PNG to create an SVG version. It should really be done with gnuplot (which I'll try this week, haven't used it before). GNUplot can apparently export as SVG. I'll also try creating a 3d plot in geogebra, and exporting to SVG.

(Also, I live in the UK, not US). M∧Ŝc²ħεИ_τlk 19:07, 4 July 2017 (UTC)

Thanks! How do you manage to trace so accurately? My tracings always look horrible when I've attempted them. :-( Stigmatella aurantiaca (talk) 19:26, 4 July 2017 (UTC)

Draw an approximate SVG line over the image, then only add as many nodes as needed to bend into shape. Copy, paste, tweak nodes, repeat. Always start from exact shapes like ellipses and rectangles then deform if needed. Just experience with SVG. M∧Ŝc²ħεИ_τlk 07:40, 5 July 2017 (UTC)

I reverted File:Relativistic gravity field (physics).svg to the earlier, less obviously incorrect version. Besides the English Wikipedia, the image is used on fi.wikipedia.org, mk.wikipedia.org, no.wikipedia.org, pa.wikipedia.org, and tr.wikipedia.org. Stigmatella aurantiaca (talk) 19:39, 4 July 2017 (UTC)

No problem. It does need changing to be clearer and correct. Maybe a 2d cross-section of the trampoline analogy could work... M∧Ŝc²ħεИ_τlk 07:40, 5 July 2017 (UTC)

Question

Hey, do you remember what font you used to create File:OiintLaTeX.svg? I'd love to use it for something in LaTeX. Thanks! --Ipatrol (talk) 01:46, 15 November 2017 (UTC)

Hi very sorry for late reply, it's just the default font in LaTeX. The name of the font is "Latin Modern Roman" or "Computer Modern Roman", [1]. I think there is a package you have to use for extra maths symbols, "esint" or whatever (haven't used LaTeX for months). Hope this helps in case you haven't found the answer yet. M∧Ŝc²ħεИ_τlk 16:25, 4 December 2017 (UTC)

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