Decomposition of quantics in sums of powers

Symmetric tensors of order 3 and 4 arise more and more often in Signal Processing and Automatic Control, because of the recent complementary use of High-Order Statistics. However, very little special purpose tools are at disposal for manipulating such objects in engineering problems. In this paper, diagonalization issues are analyzed, with the help of the theory of homogeneous polynomials in several variables (i.e. quantics). A considerable number of results are known for binary questions, but too few for general cubs and quartics. Efficient numerical algorithms are also lacking.