Recent content by LizardWizard

  1. L

    How Does the Elastic Collision of Fermions Determine Gas Pressure?

    Homework Statement For a gas of N fermions of mass m confined in a volume V at a temperature ##T<E_F/kB##, consider the quantity ##<n_p>/V## as you would a classical distribution f(p,q) in the system phase space. Show that the impulse transfer of the elastic collisions of the particles with the...
  2. L

    Finding 2D Fermion Gas U/N with Temperature & Area

    Never mind, it was right all along I just got confused for some reason.
  3. L

    Validity of Equipartition Theorem

    Thanks, I'll do that, but I think the trick here was evaluating the consequences of the infinite potential. With positive x it just becomes an harmonic oscillator and I think simple conservation of energy implies the equipartition theorem. I didn't already do the calculations because my...
  4. L

    Finding 2D Fermion Gas U/N with Temperature & Area

    Homework Statement For a gas of N fermions with mass M in 2D in a region of area A in thermal equilibrium at temperature T, we are asked to find ##U/N## in fuction of ##T## and ##a=A/N##. The attempt at a solution I used ##U=\sum(<n_i>\epsilon_i) = \sum(\exp(\beta(\mu-\epsilon_i))\epsilon_i...
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    Validity of Equipartition Theorem

    I just have one question regarding the calculations. The integrals are defined for ##H<E## or we can also use ##E<H<E+\Delta##. In a region where a term of ##H## is infite, isn't the entire integral "broken" right off the bat? I mean, unless there's something I'm missing, ##dH/dQ_i## comes out...
  6. L

    Validity of Equipartition Theorem

    I'll give it a shot, the problem is that in my textbook they don't specify the Hamiltonian they use but I'll try doing the calculations myself. Do you mind giving me the final answer so I have something to compare my calculations to when I'm done?
  7. L

    Validity of Equipartition Theorem

    Our syllabus follows Statistical Mechanics (Kerson, Huang) so that's the demonstration we used. As for the mathematical concepts used, integrals and averages I guess? For the sake of brevity here's a printscreen of the last part of the demonstration. The Hamiltonian we are given is of the...
  8. L

    Validity of Equipartition Theorem

    Undergrad Statistical Physics course, we covered the demonstration of the equipartition theorem, if that's of any help.
  9. L

    Validity of Equipartition Theorem

    So I have this question that goes like this, for a classical 1D system we are given an Hamiltonian of the form of an Harmonic Oscilator. However the term for the potential is infite when ##x\leq0## and the usual harmonical oscillator potential otherwise. The question is: is the equipartition...
  10. L

    Average of Momentum for 1D Quantum Harmonic Oscillator

    Oh I see, I found it weird because I have an example from class that makes uses it the way I said, but in the case we only had two possible n-states 0 and 1 instead of a generic integer n, I suposse that's what makes the difference. Okay, I redid the calculations and this pretty much breaks all...
  11. L

    Average of Momentum for 1D Quantum Harmonic Oscillator

    I knew there was a reason I didn't include the |n+2> term in the first place. However what exactly is wrong about that other result? It follows from applying ##\hat a |\psi_n>= \sqrt {n} |\psi_{n-1}>## to |n+1>
  12. L

    Average of Momentum for 1D Quantum Harmonic Oscillator

    That would be ##\sqrt n |n>## but I think I did forget the terms for ##\hat a^\dagger|n+1>## and <n+1| which would be ##\sqrt{n+2}|n+2>## and the corresponding bra.
  13. L

    Average of Momentum for 1D Quantum Harmonic Oscillator

    For a 1D QHO we are given have function for ##t=0## and we are asked for expectation and variance of P at some time t. ##|\psi>=(1/\sqrt 2)(|n>+|n+1>)## Where n is an integer So my idea was to use Dirac operators ##\hat a## and ##\hat a^\dagger## and so I get the following solution ##<\hat...
  14. L

    Finding the State of a Quantum System with Given Hamiltonian and Observable

    Ok, I understand. I'll go try it one more time now and see if it works out.
  15. L

    Finding the State of a Quantum System with Given Hamiltonian and Observable

    I see, could you psot your solution then perhaps?
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