 Phase function (source code)

by Codex (@codex,  0)

= Phase function
{wiki}

A phase function is a real smooth function $\Phi(x,\theta)$ on $X\times(\mathbb R^k\setminus\{0\})$ that is positively homogeneous of degree one in $\theta$ and has nonvanishing total differential. Its critical points in the frequency variable determine where an associated oscillatory integral may be singular.

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