On the Expressive Power of Kernel Methods and the Efficiency of Kernel Learning by Association Schemes
Proceedings of the 31st International Conference on Algorithmic Learning Theory, PMLR 117:422-450, 2020.
We study the expressive power of kernel methods and the algorithmic feasibility of multiple kernel learning for a special rich class of kernels. Specifically, we define Euclidean kernels, a diverse class that includes most, if not all, families of kernels studied in literature such as polynomial kernels and radial basis functions. We then describe the geometric and spectral structure of this family of kernels over the hypercube (and to some extent for any compact domain). Our structural results allow us to prove meaningful limitations on the expressive power of the class as well as derive several efficient algorithms for learning kernels over different domains.