On $2k$-Hitchin's equations and Higgs bundles: a survey

We study the $2k$-Hitchin equations introduced by Ward \cite{Ward 2} from the geometric viewpoint of Higgs bundles. After an introduction on Higgs bundles and $2k$-Hitchin's equations, we review some elementary facts on complex geometry and Yang-Mills theory. Then we study some properties of holomorphic vector bundles and Higgs bundles and we review the Hermite-Yang-Mills equations together with two functionals related to such equations. Using some geometric tools we show that, as far as Higgs bundles is concern, $2k$-Hitchin's equations are reduced to a set of two equations. Finally, we introduce a functional closely related to $2k$-Hitchin's equations and we study some of its basic properties.