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age 23
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seen Jul 28 at 0:59

May
24
comment Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
@joshphysics Thanks, this is very helpful. So you're saying that $\partial_i = \frac{\partial}{\partial x^i}$ and $\partial^i = g^{ii} \frac{\partial}{\partial x^i}$ (not summing over $i$, and I guess the metric has to be diagonal)?
May
24
comment Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
So Peter, you're saying the natural correspondence is, e.g.,$\frac{\partial}{\partial y} \leftrightarrow \frac{\partial}{\partial x_2}$?
May
24
awarded  Supporter
May
24
accepted Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
May
24
comment Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
I see. Now that I think about it, we didn't actually discuss the difference between $\partial_\mu$ and $\partial^\mu$. Is the only difference a minus sign in the spatial part?
May
24
asked Explicit form of $\gamma^\mu \partial_\mu$ in the Dirac equation
Aug
26
awarded  Scholar
Aug
26
accepted Why does heterodyne laser Doppler vibrometry require a modulating frequency shift?
Aug
24
awarded  Editor
Aug
24
revised Why does heterodyne laser Doppler vibrometry require a modulating frequency shift?
added 6 characters in body
Aug
24
comment Why does heterodyne laser Doppler vibrometry require a modulating frequency shift?
I'm not immediately making the connection to my question. Even without the modulating frequency, it is still a heterodyne technique involving the frequencies $f_0$ and $f_0+f_d$ instead of $f_0$ and $f_0+f_b+f_d$.
Aug
24
awarded  Student
Aug
24
asked Why does heterodyne laser Doppler vibrometry require a modulating frequency shift?