Quasipositive pretzels
A {quasipositive} surface in \(S^3\) is a surface which is generated from a 2-disk \(D^2\) by plumbing positive Hopf annuli \(A(0,-1)\) and passing to \(\pi_1\)-injective subsurfaces. In some sense, quasipositive surfaces are analogues in \(S^3\) of pieces of complex plane curve in \(D^4\subset C^2\). The notion of quasipositivity has been introduced by the author and explored in several of his previous papers. In this paper, he gives a necessary and sufficient condition for an oriented pretzel surface to be quasipositive. From this condition, he obtains an estimate for the slice genus of the boundary of an oriented pretzel surface.
scientific article; zbMATH DE number 1624910