Can you please help me understand what this equation means (and proof), and what exactly $\delta_{k,0}$ means. $$\sum_{k} e^{ik} = N\delta_{k,0}$$ where $N$ is some constant. I found this equation when I was working on Phonons Hamiltonian to get to in form of uncoupled harmonic oscillator form.
2026-03-25 02:57:56.1774407476
Fourier Series and Delta Function
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