Recent content by orienst

  1. O

    Graduate Ground State Parity in One-Dimensional Potentials

    Must the ground state in an even potential of one dimension be the even parity?
  2. O

    Graduate Derivative of a special function

    Thanks for your reply.
  3. O

    Graduate Derivative of a special function

    Let f(x) be the following function: f(x)=\infty,if x<0 or x>a;f(x)=0,if 0<x<a. What’s the derivative of f(x) at x=0 and x=a? I know that the derivative of step function is \delta(x) , but what will occur if the jump is infinite?
    • orienst
    • Thread
    • Derivative Function
    • Replies: 4
    • Forum: Calculus
  4. O

    Graduate How do you visualize the spin of electron in your head?

    Thanks! I think what you mean is that the measurement collapse the spin state. But what does the spin vector like before your measurement?
  5. O

    Graduate How do you visualize the spin of electron in your head?

    Thanks for your reply. I’ve read your story. But I want to visualize a vector in three-dimension!
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    Graduate How do you visualize the spin of electron in your head?

    Thanks, Demystifier !Perhaps I didn’t express clearly. When I say “a vector a which has the same projection in any direction and at any time”, I mean I’ve made a measurement in a random direction at some time. Certainly I will get \hbar/2 or -\hbar/2. So I say that the electron spin has...
  7. O

    Undergrad Degree of freedom of two point mass

    If I have two point mass moving on a track, we say that this system has 2 degrees of freedom, because we need two independent variable to locate the point mass. But what’s the number of DOF if their (the two point mass) distance was determined? Is it one? If so, which variable can locate the two...
    • orienst
    • Thread
    • Degree Degree of freedom Mass Point
    • Replies: 1
    • Forum: Mechanics
  8. O

    Graduate Commutation relations of P and H

    Can we always calculate the commutation relations of two observables? If so, what’s the commutator of P (momentum) and H (Hamiltonian) in infinite square well, considering that the momentum is not a conserved quantity?
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    Graduate How do you visualize the spin of electron in your head?

    How do you visualize the spin of electron in your head? I can’t imagine such a vector which has the same projection in any direction and at any time. Is it an understandable object in three dimension?
  10. O

    Graduate What are the minimal conditions for a non-relativistic quantum theory?

    But t is not a dynamic observable.
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    Graduate Physical interpretation of operators in QM?

    Why we use arrow for vector? I think it’s only am instrument. Use the appropriate tools to make work clear, that’s what we should do when we learn physics. We mustn’t use operators, we can use matrix instead.
  12. O

    Graduate What is Velocity in Quantum Mechanics?

    Anyone who majored experimental physics can tell me how to measure the momentum in the laboratory ?
  13. O

    High School Why do positive and negative charges attract?

    Law of Gravity！Why？
  14. O

    Graduate What is Velocity in Quantum Mechanics?

    You are calculating the velocity using the classical mechanics. I don't think you can use macroscopic objects to explain the microscopic phenomenon.
  15. O

    Graduate What is Velocity in Quantum Mechanics?

    If a "particle" in a momentum eigenstate, then according to the uncertain principal, the particle’s position has the biggest uncertainty. It may appear everywhere. Then you say that the particle has an exact velocity… I can’t understand that.