L2

L2, L², L02, L II, L.2 or L-2 may be :

In computing

In astronomy and space exploration

Aircraft

Square-integrable function

In mathematics, a square-integrable function, also called a quadratically integrable function, is a real- or complex-valued measurable function for which the integral of the square of the absolute value is finite. Thus, if

then ƒ is square integrable on the real line . One may also speak of quadratic integrability over bounded intervals such as [0, 1].

An equivalent definition is to say that the square of the function itself (rather than of its absolute value) is Lebesgue integrable. For this to be true, the integrals of the positive and negative portions of the real part must both be finite, as well as those for the imaginary part.

Often the term is used not to refer to a specific function, but to a set of functions that are equal almost everywhere.

Properties

The square integrable functions (in the sense mentioned in which a "function" actually means a set of functions that are equal almost everywhere) form an inner product space with inner product given by

where