Recent content by zhouhao

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    I Why the velocity operator commutes with position (Dirac equation)

    In classic mechanic,if we regard ##v_i## as a field ##v_i(t,x_1,x_2,x_3,x_4)##, the poisson braket ##(v_i,x_i)=\frac{\partial{v_i}}{\partial{p_i}}=\frac{\partial{v_i}}{\partial{x_i}}\frac{\partial{x_i}}{\partial{p_i}}+\frac{\partial{v_i}}{\partial{t}}\frac{\partial{t}}{\partial{p_i}}=0##, so...
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    I Why the velocity operator commutes with position (Dirac equation)

    ##\hat{v}_i=c\hat{\alpha}_i## commute with ##\hat{x}_i##, ##E^2={p_1}^2c^2+{p_2}^2c^2+{p_3}^2c^2+m^2c^4## But in classical picture,the poisson braket...
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    I Why not calculate the "trajectory" of a wave function

    Thanks.I think Bohmian mechanics is helpful to me.Could help me with another question below? ##\psi## is a solution of Schrodinger eqution. When ##\hbar \rightarrow 0##,##{\psi}(x,t) \rightarrow {\rho}(x,t)e^{\frac{i}{\hbar}S(x,t)}## Define...
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    I Why not calculate the "trajectory" of a wave function

    Thanks. How about this way. Classic Mechanic : 1,wave function (##\hbar \rightarrow 0##) is ##\psi \rightarrow \exp{\frac{i}{\hbar}S(x,t)}##; 2,we get wave function from Hamilton-Jaccobi equation with boundary condition...
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    I Why not calculate the "trajectory" of a wave function

    The classic limit of Schrodinger equation is hamilton-jacobi eqution. Wave function's classic limit is ##\exp{\frac{i}{\hbar}S(x,t)}##,##S(x,t)## is the action satisfying hamilton-jaccobi eqution. However, a particle travels along single trajectory of ##S(x,t)##, Why not make some constrains...
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    I Why not describing the radiatation of atom spectrum by TDSE

    Thanks! I means with the perturbation added, the atom in ##{\phi}_n## with time evolving to be fould in ##\Psi=\sum\limits_{m=0}^{\infty}a_m(t){\phi}_m\exp{(-\frac{i}{\hbar}{E_m}t)}##,this is a mixture of many eigenstates.However,as the book said,the atom would be found at another eigenstate in...
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    I Why not describing the radiatation of atom spectrum by TDSE

    Thanks.I check my book and I am mistaken.But I am still confused. As the book said, ##{\phi}_n## is the eigenstate of time-independent schrodinger equation with eigenvalue ##E_n##. Adding the time-dependent perturbation ##{\hat{H}}^{'}(t)##, wave function becomes...
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    I Why not describing the radiatation of atom spectrum by TDSE

    The radiation of an atom was interpreted by time-independent schrodinger equation:electron was transformed from high energy level state to lower and emit a photon.Could we treat this process through a wavefunction ##{\psi}(t)##? Before emiting,the system's wavefunction is ##{\psi}(0)## and after...
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    Calculate reaction heat from quantum mechanics

    Homework Statement I have some doubts about the method constructing chemical reaction process of quantum mechanics in the referencehttp://www.southampton.ac.uk/assets/centresresearch/documents/compchem/DFT_L2.pdf, for the example of ##H_2O## molecular dissociation to ##H^+## and ##OH^-## ions...
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    The Kirchhoff diffraction formula with small wavelength

    Homework Statement The fresnel-kirchhoff diffraction formula could explain diffraction,I think it should also produce the result with relatively small wavelength and large width slit in which case there is no diffraction. Homework Equations...
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    Why wave function is probability of particle existence

    Thanks very much.I still want to get deeper.I think two ways to understand the double-slit electron diffraction only to get both stuck. 1,Solving Schordinger equation to get the wavefunction:boundary condition is necessary.But I have no ideas to set a boundary condition. 2,Regard slit as point...
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    Why wave function is probability of particle existence

    Thanks very much!It seems that there is more precise interpretation for electron diffraction.Could you tell me? Nice.I try to figure out the ##A(x,t)##,failed with there consideration,because whether or not measure the limited angle of electrons confuse me: 1,if an electron's path could not be...
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    Why wave function is probability of particle existence

    I exactly missed something.The wave function ##{\phi}(x,t)=Ae^{\frac{i}{\hbar}S(x,t)}## spread over all space-time,it has value at arbitrary (x,t).Some improvements needed...I think...
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    Why wave function is probability of particle existence

    Homework Statement I post here to check if I am in the right way to understand this point in the book. The wave function of free particle is ##Ae^{\frac{i}{\hbar}(px-Et)}##.This could be regarded as ##{\phi}(x,t)=Ae^{\frac{i}{\hbar}S(x,t)}##. ##S(x,t)## is the free particle's least action...
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    I How Fermat's principle interprets diffraction and interference

    <Moved from the homework section> 1. Homework Statement I have read several chapters of De Brogile's article "the theory of quanta".The motion of a particle could be analogious to a ray in general optics.This is an analogy between Maupertui's principle and fermat's principle. How to use this...
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