INTEGRAL TRANSFORM

mathematical operator that produces a new function f(y) by integrating the product of an existing function F(x) and a so-called kernel function K(x, y) between suitable limits. The process, which is called transformation, is symbolized by the equation f(y) = K(x, y)F(x)dx. Several transforms are commonly named for the mathematicians who introduced them: in the Laplace transform, the kernel is exp(-xy) and the limits of integration are zero and plus infinity; in the Fourier transform, the kernel is (2p)-1/2exp(-ixy) and the limits are minus and plus infinity. (See also Fourier transform; Laplace transform.) The value of integral transforms lies in the simplification that they bring about, most often in dealing with differential equations subject to particular boundary conditions. Proper choice of the class of transformation usually makes it possible to convert not only the derivatives in an intractable differential equation, but the boundary values, as well, into terms of an algebraic equation that can be easily solved. The solution obtained is, of course, the transform of the solution of the original differential equation, and it is necessary to invert this transform to complete the operation. For the common transformations, tables are available that list many functions and their transforms.