Definition of a P-interpolating space of hierarchical bases of finite elements on the pyramid

This article shows in detail how to construct in a simple and ordered way a set of rational functions defined on the pyramid topology. The set of functions is parameterized by an integer p. It is shown that these functions, defined in a hierarchical way, constitute a basis for a complete polynomial interpolation space of degree p on the pyramid domain. In order to help this definition we use a denumerable sequence of orthogonal polynomials defined on an interval of the real line. A priori, any increasing sequence of polynomials in one variable can be used. The bases are constructed to be used in the class C0 method of finite elements. The rational functions thus defined can be combined to represent any polynomial of degree p. Thus, given an arbitrary number p, one defines a finite element whose geometry is a pyramid that has associated a complete interpolation space of degree p. Moreover, this element is adequate to be used with the p-adaptive technique on heterogeneous meshes of finite elements hierarchical.