Rayleigh-Ritz Variational Technique

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A technique for computing eigenfunctions and eigenvalues. It proceeds by requiring

 J=int_a^b[p(x)y_x^2-q(x)y^2]dx
(1)

to have a stationary value subject to the normalization condition

 int_a^by^2w(x)dx=1
(2)

and the boundary conditions

 py_xy|_a^b=0.
(3)

This leads to the Sturm-Liouville equation

 d/(dx)(p(dy)/(dx))+qy+lambdawy=0,
(4)

which gives the stationary values of

 F[y(x)]=(int_a^b(py_x^2-qy^2)dx)/(int_a^by^2wdx)
(5)

as

 F[y_n(x)]=lambda_n,
(6)

where lambda_n are the eigenvalues corresponding to the eigenfunction y_n.

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