Slowly varying envelope approximation

<p>In <a href="/facts/Physics/a7aH2y08">physics</a>, slowly varying envelope approximation (SVEA, sometimes also called slowly varying asymmetric approximation or SVAA) is the assumption that the <a href="/facts/Envelope_(waves)/3JsLqPoh">envelope</a> of a forward-travelling <a href="/facts/Wave/fU0HH6St">wave</a> pulse varies slowly in time and space compared to a <a href="/facts/Period_(physics)/QUSbPaW8">period</a> or <a href="/facts/Wavelength/kcJU0ymz">wavelength</a>. This requires the <a href="/facts/Spectrum/wPUjkpqI">spectrum</a> of the signal to be <a href="/facts/Narrow-band/76nBsRml">narrow-banded</a>—hence it is also referred to as the narrow-band approximation.
</p><p>The slowly varying envelope approximation is often used because the resulting equations are in many cases easier to solve than the original equations, reducing the order of—all or some of—the highest-order <a href="/facts/Partial_derivative/JWHsBkAu">partial derivatives</a>. But the validity of the assumptions which are made need to be justified.
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Slowly varying envelope approximation open-in-new

Slowly varying envelope approximation