释义 |
Green's FunctionLet
 | (1) |
be a differential Operator in 1-D, with Continuous for , 1, ..., on the interval , and assume we wish to find the solution to the equation
 | (2) |
where is a given Continuous on . To solve equation (2), we look for a function such that , where
 | (3) |
This is a Convolution equation of the form
 | (4) |
so the solution is
 | (5) |
where the function is called the Green's function for on .
Now, note that if we take , then
 | (6) |
so the Green's function can be defined by
 | (7) |
However, the Green's function can be uniquely determined only if some initial or boundary conditions are given.
For an arbitrary linear differential operator in 3-D, the Green's function is defined byanalogy with the 1-D case by
 | (8) |
The solution to is then
 | (9) |
Explicit expressions for can often be found in terms of a basis of given eigenfunctions by expandingthe Green's function
 | (10) |
and Delta Function,
 | (11) |
Multiplying both sides by and integrating over space,
 | (12) |
 | (13) |
so
 | (14) |
By plugging in the differential operator, solving for the s, and substitutinginto , the original nonhomogeneous equation then can be solved. References
Arfken, G. ``Nonhomogeneous Equation--Green's Function,'' ``Green's Functions--One Dimension,'' and ``Green's Functions--Two and Three Dimensions.'' §8.7 and §16.5-16.6 in Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 480-491 and 897-924, 1985. |