We show that any differential operator of the form $L(y)=\sum_{k=0}^{k=N}
a_{k}(x) y^{(k)}$, where $a_k$ is a real polynomial of degree $\leq k$, has all
real eigenvalues in the space of polynomials of degree at most n, for all n.
The eigenvalues are given by the coefficient of $x^n$ in $L(x^{n})$.
We revisit basics of classical Sturm-Liouville theory and, as an application,
recover Bochner's classification of second order ODEs with polynomial
coefficients and polynomial solutions by a new argument. We also outline how a
wider class of equations with polynomial solutions can be obtained by allowing
the weight to become infinite at isolated points:the Jacobi equation, in
general, is of this type.
We revisit basics of classical Sturm-Liouville theory and, as an application,
recover Bochner's classification of second order ODEs with polynomial
coefficients and polynomial solutions by a new argument. We also outline how a
wider class of equations with polynomial solutions can be obtained by allowing
the weight to become infinite at isolated points:the Jacobi equation, in
general, is of this type.
Lie symmetry method is applied to find analytic solutions of
initial-boundary-value problems of transient conduction in semi-infinite solid
with constant surface temperature or constant heat flux condition. The
solutions are obtained in a manner highlighting the systematic procedure of
extending the symmetry method for a PDE to investigate BVPs of the PDE. A
comparative analysis of numerical and closed form solutions is carried out for
a physical problem of heat conduction in a semi-infinite solid bar made of AISI
304 stainless steel.