Sinc Function - Relationship To The Dirac Delta Distribution

Relationship To The Dirac Delta Distribution

The normalized sinc function can be used as a nascent delta function, meaning that the following weak limit holds:

This is not an ordinary limit, since the left side does not converge. Rather, it means that

\lim_{a\rightarrow 0}\int_{-\infty}^\infty \frac{1}{a}\textrm{sinc}(x/a)\varphi(x)\,dx = \varphi(0),

for any smooth function with compact support.

In the above expression, as a approaches zero, the number of oscillations per unit length of the sinc function approaches infinity. Nevertheless, the expression always oscillates inside an envelope of ±1/(π a x), and approaches zero for any nonzero value of x. This complicates the informal picture of δ(x) as being zero for all x except at the point x = 0 and illustrates the problem of thinking of the delta function as a function rather than as a distribution. A similar situation is found in the Gibbs phenomenon.

Read more about this topic:  Sinc Function

Famous quotes containing the words relationship to, relationship and/or distribution:

    Film music should have the same relationship to the film drama that somebody’s piano playing in my living room has to the book I am reading.
    Igor Stravinsky (1882–1971)

    Only men of moral and mental force, of a patriotic regard for the relationship of the two races, can be of real service as ministers in the South. Less theology and more of human brotherhood, less declamation and more common sense and love for truth, must be the qualifications of the new ministry that shall yet save the race from the evils of false teaching.
    Fannie Barrier Williams (1855–1944)

    The man who pretends that the distribution of income in this country reflects the distribution of ability or character is an ignoramus. The man who says that it could by any possible political device be made to do so is an unpractical visionary. But the man who says that it ought to do so is something worse than an ignoramous and more disastrous than a visionary: he is, in the profoundest Scriptural sense of the word, a fool.
    George Bernard Shaw (1856–1950)