= Wavevector distribution of an infinite-well ground state
{title2=$p(k)=4\pi L\cos^2(kL/2)/[\pi^2-(kL)^2]^2$}
A centred width-$L$ <infinite square well> has <ground state> <wavefunction> $\sqrt{2/L}\cos(\pi x/L)$ inside and zero outside. Its <momentum representation in quantum mechanics> follows from the <Fourier transform of a truncated cosine>. The <probability density> in the title has removable singularities at $k=\pm\pi/L$, with limit $L/(4\pi)$, and an oscillatory $k^{-4}$ tail envelope. The distribution is even, with $\langle k\rangle=0$ and $\langle k^2\rangle=\pi^2/L^2$.
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