Real algebraic overtwisted contact structures on 3-spheres

Abstract

A real algebraic link in the 3-sphere is defined as the zero locus in the 3-sphere of a real algebraic function from $\mathbb{R}^4$ to $\mathbb{R}^2$. A real algebraic open book decomposition on the 3-sphere is by definition the Milnor fibration of such a real algebraic function, in case it exists. We prove that every overtwisted contact structure on the 3-sphere with positive three dimensonal invariant $d_3$ (apart from possibly 9 exceptions) are real algebraic. Our construction shows in particular that the pages of the associated open books are planar.