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Schroedinger Equation

  1. Oct 19, 2013 #1
    Hi all, I am a 10th grade student who has a basic grasp on matrices, differential calculus and can integrate. I am having trouble with the Schrödinger equation (which part? where to start and just all of it)I was wondering where I could find a detailed stepwise walkthrough to the Schrödinger equation. It would be nice to have one in both one and 2 dimensions. Thanks for ANY help that I receive.

    I also don't get the iH part what are you supposed to do there? and by the way I live in a place where it's virtually impossible to get an advanced physics textbook.
     
    Last edited by a moderator: Oct 31, 2013
  2. jcsd
  3. Oct 19, 2013 #2
    Do you have any experience with wave equations? Or any partial differential equations? What about complex numbers?

    Also, there is more than one way to write the Schrödinger equation so it would be helpful if you let us know the exact equation you're talking about.
     
    Last edited by a moderator: Oct 31, 2013
  4. Oct 19, 2013 #3

    jtbell

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    The first example of solving the Schrödinger equation, that just about everybody does, is the "infinite square well" a.k.a. "particle in a box." Have you seen that yet?

    A Google search for "infinite square well" turns up lots of lecture notes, many of which unfortunately seem to assume you have a book handy, or are supplements to an in-class lecture. This page, however, seems to be mostly self-contained, and does it pretty much the way I used to do it in a second-year intro modern physics course:

    http://physicspages.com/2011/01/26/the-infinite-square-well-particle-in-a-box/

    It does make reference to another page on the time-independent SE:

    http://physicspages.com/2011/01/22/the-time-independent-schrodinger-equation/
     
  5. Oct 19, 2013 #4
    I suspect that you don't have any real experience with physics, and are trying to start off with QM. You can't fully appreciate QM without having studied (bare-minimum) classical mechanics. It's very much like trying to watch a movie in a foreign language without even knowing the alphabet.

    If you're really dead-set on trying to learn QM, you could try a book like Griffiths' "Introduction to Quantum Mechanics", but I don't think anybody here would advise this, especially since you haven't told us about your physics background.
    ##\hat{H} = -\frac{\hbar ^2}{2m}\nabla ^2 +V## is the Hamiltonian operator, and ##i## is the imaginary number.
     
    Last edited: Oct 19, 2013
  6. Oct 20, 2013 #5
    the only thing I have experience with is calculus, any website that teaches the higher math in a format that's easy to understand? Plus what's the inverted triangle?
     
  7. Oct 20, 2013 #6

    jtbell

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    The "inverted triangle" is the nabla operator. In Schrödinger's equation, you see its square:
    $$\nabla^2 \psi = \frac{\partial^2 \psi}{\partial x^2} + \frac{\partial^2 \psi}{\partial y^2} + \frac{\partial^2 \psi}{\partial z^2}$$

    Have you studied partial derivatives yet? (e.g. ##\partial \psi / \partial x##)

    In the USA, people usually learn these in the third semester of an undergraduate calculus course. It often goes by the name "vector calculus." Even introductory QM books and web pages assume that you have studied that much calculus, and are at least acquainted with the basic ideas of differential equations.
     
  8. Oct 20, 2013 #7
    I can do differential equations, I have not done pde's yet though...any links? sorry to bother.
     
  9. Oct 20, 2013 #8

    jtbell

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    You really don't need to know anything special about PDEs in order to start learning about solving Schrödinger's equation. If you know what partial derivatives are, you'll be OK.

    In the standard examples that all introductory QM textbooks use, the first thing they do is use the "separation of variables" technique to convert the partial differential equation into two or more ordinary differential equations. The second page that I linked to above describes that.
     
  10. Oct 20, 2013 #9
    If I can solve Schrödinger eqn can I then solve any physics equation? aside from ones in general relativity.
     
  11. Oct 20, 2013 #10
    No.

    It's just one equation. There are inumerous more to solve too.

    Some equations even have no analytical solution.
     
  12. Oct 20, 2013 #11
    Like what?
     
  13. Oct 20, 2013 #12
  14. Oct 20, 2013 #13

    jtbell

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    Even Schrödinger's equation has analytical solutions (ones that you can write down formulas for) for only a few highly symmetric situations. In general, you have to use numerical methods to generate the solution point by point and e.g. make a graph of it.
     
  15. Oct 20, 2013 #14
    I don't mean to be rude, but what are you talking about? I seriously can't see a point in studying QM without knowing any physics beforehand. Asking a question like this is ridiculous (and also extremely vague). The answer is a big "NO". As others have said, most ODEs,PDEs can't be solved analytically, and Schrödinger's equation is not "One equation to rule them all"

    We have countless people coming on the forums, both kids and adults, asking to "learn" quantum mechanics when they haven't studied any prior physics/math. There's a reason QM is not taught (generally) as a first year course. Physics is way more than mathematics. Just because you have experience with calculus (and I suspect little experience, too) doesn't mean you understand the physics!

    I appreciate that you are eager to study physics, but please DO IT THE RIGHT WAY. A great first textbook is An Introduction to Mechanics. The math is simple, but the physics is fairly advanced for a first year text. It doesn't cover Lagrangian mechanics, but you can use another book for that.
     
  16. Oct 20, 2013 #15
    True astrum, but what I meant was assuming you learned math in the same sequence taught by schools up until integral calculus could you solve the vast majority of physics equations aside form topological ones or ones that require tensors? i.e. does it get harder than pde's and tensors?

    I really don't have money for textbooks, or in general. Hence me asking for links.
     
    Last edited by a moderator: Oct 31, 2013
  17. Oct 20, 2013 #16
    Yeah, the answer is still no. Linear Algebra is a very important field that is used all the time in physics, you'll encounter a lot in QM (although not too much in Griffiths QM).

    I'm sure you can use "other means" for getting textbooks. Linking illegal content will get your post removed, but I'm sure you're resourceful enough to do it on your own.
     
  18. Oct 20, 2013 #17
    Many professors and universities post excellent lectures and lecture notes online, and being good at googling for these is also a good method for learning. A good way to filter for these is to put "site:.edu" in with your google search, automatically returning results from an .edu domain so that you're more likely to return lecture notes.

    My undergrad quantum mechanics professor posted all of his course books for free online:
    http://farside.ph.utexas.edu/teaching.html
     
  19. Oct 20, 2013 #18
    Hey, I can do it now thanks to YouTube! :) Thanks for all your help
     
  20. Oct 20, 2013 #19

    meBigGuy

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