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Fourier Transforms in Stellar Astrophysics
Howard S. Cohl
Lawrence Livermore National Laboratory
Livermore, California, U.S.A.
Precise efforts in theoretical astrophysics are needed to fully understand
the mechanisms which govern the structure, stability, dynamics, formation,
and evolution of differentially rotating stars. Direct computation of the
physical attributes of a star can be facilitated by the use of highly compact
azimuthal and separation angle Fourier formulations of the linear PDE's of
mathematical physics. These mathematical reformulations are through
Green's functions which represent the inhomogeneous contribution to the
PDE from a point source or sink. The Green's functions for the linear PDE's
of mathematical physics are of great importance in many areas of modern physics
such as in diffusion and wave phenomenon. The Green's function for Laplace's
equation is used in classical and quantum physics formulations of the Coulomb
and Newtonian interactions. We express the Green's function formulation
as sums and integrals over eigenfunction separated solutions in those specific
coordinate systems which allow separable solutions to these PDE's. Those
rotationally invariant coordinate systems which allow separable solutions to
these linear PDE's are each commonly expressible in terms of the azimuthal
angle. For these rotationally invariant coordinate systems, the Green's
functions are seen to be expressible in terms of an azimuthal and separation angle
Fourier basis description. This description leads to reformulations of many
branches of theoretical physics and pure mathematics. The ultimate resolution
of these analytical investigations will be efficient algorithmic implementations
of these new schemes. We propose these methods to the 3D star community in
hope that you may continue to enjoy significantly improved economical and
precise boundary values for studies of analytical and numerical 3D stellar
astrophysics. Numerical implementations of this approach for gravity will be
presented in terms of the 3D djehuty context and describe current research
investigations.
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