FTP, name this type of generalized function that can, in principle, be found for an operator L using the equation L operating on g of r given r-prime equals delta of r minus r-prime, and its namesake's second identity.
For the Helmholtz equation with constant k, this distribution may be succinctly defined as the sum over all n of the product of the nth eigenfunction at the field and source points, divided by the quantity k2 ("kay-squared") minus the nth eigenvalue squared. This is, in general, the kernel such that its convolution with the density function in an operator equation yields the solution to that equation. FTP, name this type of generalized function that can, in principle, be found for an operator L using the equation L operating on g of r given r-prime equals delta of r minus r-prime, and its namesake's second identity.
For the Helmholtz equation with constant k, this distribution may be succinctly defined as the sum over all n of the product of the nth eigenfunction at the field and source points, divided by the quantity k2 ("kay-squared") minus the nth eigenvalue squared.
{Green’s function}