... amplitude

Appendices A and B are only available in electronic form at http://www.edpsciences.org

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... intensity

Throughout the text we refer to the quantity defined by $\tilde \phi(\nu)$ in Eq. (4) as the (complex) wave amplitude at frequency $\nu$, while the quantity $\vert \tilde \phi(\nu) \vert^2(t)$ is the intensity of the radiation at frequency $\nu$ and time t. Thus intensity variations refer to changes in the quantity $\vert\tilde \phi (\nu) \vert(t)$ with time.

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