Principles of Quantum Mechanics · Problem 2.7.5

All Is Not Well with Classical Mechanics — R. Shankar

Physics — Quantum Mechanics · canonical-transformations

Problem

Show that the polar variables ρ=(x2+y2)1/2\rho = (x^2 + y^2)^{1/2}, ϕ=tan⁡−1(y/x)\phi = \tan^{-1}(y/x), pρ=e^ρ⋅p=xpx+ypy(x2+y2)1/2,pϕ=xpy−ypx (=lz)p_\rho = \hat{e}_\rho \cdot \mathbf{p} = \frac{xp_x + yp_y}{(x^2+y^2)^{1/2}}, \qquad p_\phi = xp_y - yp_x\ (=l_z) are canonical. (e^ρ\hat{e}_\rho is the unit vector in the radial direction.)

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