The h Bar

1:58 PM

$\langle \psi_{100} \vert x^2 \vert\psi_{100} \rangle = \dfrac{1}{\pi a^3} \int r^2 \cos^2 \theta \sin^2 \phi e^{-2r/a} r^2 \sin \theta dr d\theta d\phi = \dfrac{1}{\pi a^3}[\int_{0}^{\infty} r^4 e^{-2r/a} dr \int_{0}^{\pi} \cos^2 \theta \sin \theta d\theta \int_0^{2\pi} \sin^2 \phi d\phi] =\\ = \dfrac{1}{\pi a^3} \dfrac{4!}{(2/a)^5} \dfrac{2}{3} \pi=a^2/2$

It should be $a^2$, where did I screw up?

Anonymous

3:11 PM

@JohnRennie By any chance do you know how to convert .ppm images to other formats like jpeg or eps or pdf?

Anonymous

I got a C program which produces a .ppm image

Anonymous

But I can't use that format in other places

Anonymous

(I mean that I could simply use "Snipping tool" or something like that, but I want to retain the image quality)

John Rennie

@Blue What format is ppm?

Anonymous

Netpbm format

A Netpbm format is any graphics format used and defined by the Netpbm project. The portable pixmap format (PPM), the portable graymap format (PGM) and the portable bitmap format (PBM) are image file formats designed to be easily exchanged between platforms. They are also sometimes referred to collectively as the portable anymap format (PNM), not to be confused with the related portable arbitrary map format. == History == The PBM format was invented by Jef Poskanzer in the 1980s as a format that allowed monochrome bitmaps to be transmitted within an email message as plain ASCII text, allowing it...

danielunderwood

3:13 PM

gimp? imagemagick?

John Rennie

@Blue Aha, Paint Shop Pro can open those and convert them.

Anonymous

I don't have prior experience with gimp :/

Anonymous

(And don't have Photoshop installed on my PC either)

John Rennie

@Blue didn't I give you a copy of Paint Shop Pro?

Anonymous

I can download gimp on linux it seems

Anonymous

3:15 PM

@JohnRennie Oh, I was reading that as "Photoshop" :P

Anonymous

oops

Anonymous

Yeah, lemme try

Anonymous

Switching to Windows... one moment

John Rennie

@Blue bloody users! :-)

2

danielunderwood

I think it would just be open -> export. Don't really know about quality though. imagemagick (or however it's spelled) is a cli tool that a lot of people seem to use if you need to convert a bunch or something

Yeah users always go around breaking software

Have you guys that watch online lectures tried increasing playback speed? I thought I'd just miss a bunch of stuff, but I seem to have gotten used to it and can pause/slow down for interesting or difficult parts.

Anonymous

3:23 PM

@JohnRennie It seems you had given me a copy of MS Paint (since my PC only had Paint 3D) and not "Paint Shop Pro" :P

John Rennie

Do you want a copy of Paint Shop Pro? Or will you just use Gimp?

Anonymous

Lemme try to use gimp first, just downloaded it on Ubuntu

Anonymous

Will come back if I get stuck :P

Anonymous

Anonymous

Opened the image on gimp, where's the export option? @danielunderwood

Lozansky

3:31 PM

Ctrl+E?

danielunderwood

It's playing hide and seek of course!

Lozansky

Or cmd+E

danielunderwood

Ctrl+E should work as above, but it would be in the file menu above your image

Anonymous

Umm, so it doesn't have any .pdf or .eps export option...so I guess I should convert to jpeg first?

Anonymous

@Lozansky Thanks

danielunderwood

3:34 PM

Try to give it a pdf extension. It lists pdf in the expandable box for me

It also lists eps if you prefer that

Anonymous

Damn, they wrote the full form of PDF instead

Anonymous

Lol

Anonymous

@danielunderwood Thanks a ton, it worked! :D

danielunderwood

Wooo!

The real question is what the image is for. It looks like a QR code gone crazy!

Anonymous

Heh, they're just some black and white clusters....like in $Z^2$ percolation models

Anonymous

3:41 PM

Not a QR code XD

Anonymous

I'm trying to make a it a bit more colorful like this ^

Anonymous

Or maybe like this:

Anonymous

(that might be a bit too much :P)

danielunderwood

3:46 PM

Kind of looks like you generated random clusters lol

Anonymous

Indeed, random matrices/lattices

danielunderwood

It might help if I knew what percolation models were. May give me something to google a bit later. This may be a silly question, but does it have anything to do with like coffee percolation? Like liquid going through granular materials?

Anonymous

@danielunderwood Sure, that's one application. Site percolations are prevalent in several areas of condensed matter physics (especially phase transitions) and computer science (network theory). Just last month we were discussing that lightning can be modeled as a type of site percolation...so...umm...tons of interesting uses

Anonymous