Recent content by Tianwu Zang

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    Variable substitution in Langevin equation and Fokker-Planck equation

    Yes I think you get the point. It seems that Ito calculus uses a different method for changing the variables. I am really unfamiliar with this area before so your link really helps. Thanks a lot!
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    Variable substitution in Langevin equation and Fokker-Planck equation

    Dear all, I have a question about the variable substitution in Langevin equation and Fokker-Planck equation and this has bothered me a lot. The general Langevin equation is: $$\frac{dx}{dt}=u(x)+\sqrt{2 D(x)}\eta(t)$$ and the corresponding Fokker-Planck equation is thus: $$\frac{\partial...
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    Electric potential generated by a electric loop

    Hi all, What is the potential generated by a electric loop? I have found two ways to sovle the problem. One is since the charge density does not change with time, we can write it as \phi(\vec{r_{0}})=\oint\frac{\rho_{static}}{|\vec{r}-\vec{r_{0}}|}d\vec{l}. But what is \rho in this loop? Is...
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    Is the normal mode frequency of harmonic oscillator related to temperature?

    Hmm, I see. Your word "distribution of energy on the different modes is precisely the result of reaching equilibrium with a minimum free energy" made me clear. Thanks a lot.
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    What Is the Entropy of a Classical Oscillator System in Thermal Equilibrium?

    Homework Statement In a reservoir there are three balls. There is a spring(the weight of spring is negligible) with elastic coefficient k between each two balls(small enough, like two particles). Suppose the center of gravity of the system does not move, and the mass of each ball is m. Suppose...
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    Is the normal mode frequency of harmonic oscillator related to temperature?

    It is well known that for an isolated system, the normal mode frequency of a N-body harmonic oscillator satisfies Det(T-\omega^{2}V)=0. How about a non-isolated, fixed temperature system? In solid state physics I have learned that in crystal the frequency does not change, but the amplitude of...
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    Eigenvalue of the coherent state

    So solving the eigenvalue of matrix in infinite dimension is not the same with the process to solve the eigenvalue of matrix in finite dimension? I know the determinant of a-\alphaI is \alpha^{n} when the matrix is finite. How about the determinant when it is infinite? I am not very familiar...
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    Eigenvalue of the coherent state

    my picture cannot be displayed? try this weblink: http://www.tuchuan.com/a/2010020418032158925.jpg"
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    Eigenvalue of the coherent state

    Hi all, the annihilation operator satisfies the equation \hat{a}|n>=\sqrt{n}|n-1> and \hat{a}|0>=0 so the matrix of \hat{a} should be http://www.tuchuan.com/a/2010020418032158925.jpg and zero is the only eigenvalue of this matrix. The coherent state is defined by...
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    Vector potential in cavity of arbitrary shape

    we know that vector potential in a resonator satisfies the equation \intA(\lambda)A^{*}(\lambda^{'})dV=4\pic^{2}\delta_{\lambda\lambda^{'} So how about in cavity of arbitrary shape? Does this equation still valid? Thanks!
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