6 ms·

Notes on Quantum Mechanics

44 points by elektropionir 12y ago

graycat 12y ago
Okay, would like to read it. However, on my screen, called 14", about 12.5" wide, the text is about 100 characters per line in about 7.5" for about 13.33 characters per inch horizontally. Then with two pair of strong reading glasses and my nose 5" from the screen, I can barely read the text. A shame because about half the width of the screen is given over to just a table of contents with mostly blank space. Maybe if I had a video screen 4 feet wide? More generally, yes, I know, there is a lot of careful, sophisticated, deep work in user interface, but for the OP pages I'd like to see only about 60 characters per line and about 6 characters per inch horizontally. About 8 characters per inch is my upper limit. Sure if my screen were twice as wide, then I could get the present 13 characters per inch down to 7.5, but these days with laptops and tables, screens 25" inches wide are not near the 'median'. 13 characters per inch I just can't read without a lot of effort. Generally, in Web screens, we are free to use about all the length we want but should be very careful about using up screen width. In my start-up, each screen is just 800 pixels wide with high contrast and large fonts, about 25 pixels high on lines 35 pixels high. Here I'd like to encourage Web page designers to use larger fonts, narrower pages, and fewer characters per line.
- xxxyy 12y ago
  Can't you just Ctrl+ it?
  - graycat 12y ago
    No: The text goes off the right side of the screen, and there is no horizontal scroll bar to permit bringing the text back on the screen.
    - xxxyy 12y ago
      Oh, i see, because on my screen (1920 wide) it zooms pretty well.
- cbd1984 12y ago
  > larger fonts, narrower pages, and fewer characters per line. And I prefer the exact opposite, and neither of us are wrong. I just thought I'd get that out of the way before the usual flame war erupts, and the "your preference is objectively bad" brigade comes out citing "laws" and "studies" and "You must be just like the small group we tested on, you just don't know what you like" and so on.
  - trurl42 12y ago
    The page is unusable at lower resolutions. http://i.snag.gy/O9Abg.jpg http://i.snag.gy/O9Abg.jpg It's pretty bad.
    - cbd1984 12y ago
      Ah, the sign of a graphical designer: "No. It doesn't wrap or flow. Wrapping and flowing messes up the design I created. Everything should be pixel-perfect with how it is on my Mac."
      - ineedtosleep 12y ago
        > I just thought I'd get that out of the way before the usual flame war erupts, Then you post an ad-hominem and ignore any evidence that this site breaks the web. Bravo.
  - graycat 12y ago
    > And I prefer the exact opposite Fine with me, but here I'm not trying for anything subtle or artistic: I just want to be able to read the darned text. My suggestion of <= 60 characters per line is closer to what newspapers long preferred. My suggestion of only about 6 characters per inch horizontally on the screen is due partly to my eyes no longer being 20 years old, but really tiny fonts get fuzzy on a screen 12.5" wide with 1024 x 768 pixels. I'd be glad to have any other situation, including the one you prefer, if I could just read the darned text. I confess, I just tweaked my favorite text editor to give me 62 characters, bold, in 9" horizontally, and I like it much better than before. So, that's 6.88 characters per inch horizontally on the screen, can clearly see the difference between a comma and a period, etc. For some Web pages, I just copy the text to the system clipboard, pull it into my favorite text editor, re-flow the text back to about 60 characters per line, and just read the stuff easily. But for this piece on quantum mechanics, I guessed that there would be enough in math notation that my copy, paste, and re-flow into my 8 bit ASCII text editor wouldn't work. I'd enjoy reading the quantum mechanics if I could read the text.
elektropionir 12y ago
Submitter here. Sorry about the layout problems. I hate usability issues like these and I just did some quick fixes. Should work a bit better on narrower screens. I was more excited about the content and getting that right that I just didn't test the layout before posting (I have large monitors so my defaults were not geared toward small screen sizes). I had an eye exam today so I could literally only now see these comments since my pupils were dilated. I hope you can now get to some of the quantum mechanics stuff.
orangea 12y ago
I look forward to reading this! However, I am reading the first part of the first section (explaining the basis vectors of a linear space), and see this: http://i.imgur.com/Qizuw0K.png http://i.imgur.com/Qizuw0K.png That makes no sense to me, shouldn't it be more like this? http://i.imgur.com/iKpKgSa.png http://i.imgur.com/iKpKgSa.png Maybe I am just not familiar with the notation, though...
- elektropionir 12y ago
  You're right, it's a typo, the sum was on the wrong side. I fixed the equation. Thanks for catching it. Please let me know if you find any other issues. I wrote the original notes a while ago and I had to do some adjustments to make the LaTeX source work with MathJax so there might be other typos. BTW, |u> = u_i |e_i> would be the correct equation in Einstein notation where the u_i |e_i> would be a contraction in which the summation along repeated indices is implicit. When you're dealing with a lot of tensor multiplication this notation is very useful because of its clarity and compactness.

44 points by elektropionir 12y ago

Okay, would like to read it. However, on my screen, called 14", about 12.5" wide, the text is about 100 characters per line in about 7.5" for about 13.33 characters per inch horizontally. Then with two pair of strong reading glasses and my nose 5" from the screen, I can barely read the text. A shame because about half the width of the screen is given over to just a table of contents with mostly blank space. Maybe if I had a video screen 4 feet wide? More generally, yes, I know, there is a lot of careful, sophisticated, deep work in user interface, but for the OP pages I'd like to see only about 60 characters per line and about 6 characters per inch horizontally. About 8 characters per inch is my upper limit. Sure if my screen were twice as wide, then I could get the present 13 characters per inch down to 7.5, but these days with laptops and tables, screens 25" inches wide are not near the 'median'. 13 characters per inch I just can't read without a lot of effort. Generally, in Web screens, we are free to use about all the length we want but should be very careful about using up screen width. In my start-up, each screen is just 800 pixels wide with high contrast and large fonts, about 25 pixels high on lines 35 pixels high. Here I'd like to encourage Web page designers to use larger fonts, narrower pages, and fewer characters per line.

xxxyy 12y ago
Can't you just Ctrl+ it?
- graycat 12y ago
  No: The text goes off the right side of the screen, and there is no horizontal scroll bar to permit bringing the text back on the screen.
  - xxxyy 12y ago
    Oh, i see, because on my screen (1920 wide) it zooms pretty well.
cbd1984 12y ago
> larger fonts, narrower pages, and fewer characters per line. And I prefer the exact opposite, and neither of us are wrong. I just thought I'd get that out of the way before the usual flame war erupts, and the "your preference is objectively bad" brigade comes out citing "laws" and "studies" and "You must be just like the small group we tested on, you just don't know what you like" and so on.
- trurl42 12y ago
  The page is unusable at lower resolutions. http://i.snag.gy/O9Abg.jpg http://i.snag.gy/O9Abg.jpg It's pretty bad.
  - cbd1984 12y ago
    Ah, the sign of a graphical designer: "No. It doesn't wrap or flow. Wrapping and flowing messes up the design I created. Everything should be pixel-perfect with how it is on my Mac."
    - ineedtosleep 12y ago
      > I just thought I'd get that out of the way before the usual flame war erupts, Then you post an ad-hominem and ignore any evidence that this site breaks the web. Bravo.
- graycat 12y ago
  > And I prefer the exact opposite Fine with me, but here I'm not trying for anything subtle or artistic: I just want to be able to read the darned text. My suggestion of <= 60 characters per line is closer to what newspapers long preferred. My suggestion of only about 6 characters per inch horizontally on the screen is due partly to my eyes no longer being 20 years old, but really tiny fonts get fuzzy on a screen 12.5" wide with 1024 x 768 pixels. I'd be glad to have any other situation, including the one you prefer, if I could just read the darned text. I confess, I just tweaked my favorite text editor to give me 62 characters, bold, in 9" horizontally, and I like it much better than before. So, that's 6.88 characters per inch horizontally on the screen, can clearly see the difference between a comma and a period, etc. For some Web pages, I just copy the text to the system clipboard, pull it into my favorite text editor, re-flow the text back to about 60 characters per line, and just read the stuff easily. But for this piece on quantum mechanics, I guessed that there would be enough in math notation that my copy, paste, and re-flow into my 8 bit ASCII text editor wouldn't work. I'd enjoy reading the quantum mechanics if I could read the text.

elektropionir 12y ago

Submitter here. Sorry about the layout problems. I hate usability issues like these and I just did some quick fixes. Should work a bit better on narrower screens. I was more excited about the content and getting that right that I just didn't test the layout before posting (I have large monitors so my defaults were not geared toward small screen sizes). I had an eye exam today so I could literally only now see these comments since my pupils were dilated. I hope you can now get to some of the quantum mechanics stuff.

orangea 12y ago

I look forward to reading this! However, I am reading the first part of the first section (explaining the basis vectors of a linear space), and see this: http://i.imgur.com/Qizuw0K.png http://i.imgur.com/Qizuw0K.png That makes no sense to me, shouldn't it be more like this? http://i.imgur.com/iKpKgSa.png http://i.imgur.com/iKpKgSa.png Maybe I am just not familiar with the notation, though...

elektropionir 12y ago
You're right, it's a typo, the sum was on the wrong side. I fixed the equation. Thanks for catching it. Please let me know if you find any other issues. I wrote the original notes a while ago and I had to do some adjustments to make the LaTeX source work with MathJax so there might be other typos. BTW, |u> = u_i |e_i> would be the correct equation in Einstein notation where the u_i |e_i> would be a contraction in which the summation along repeated indices is implicit. When you're dealing with a lot of tensor multiplication this notation is very useful because of its clarity and compactness.