Lens space surgeries on A'Campo's divide knots

It is proved that every knot in the major subfamilies of J. Berge's lens space surgery (i.e., knots yielding a lens space by Dehn surgery) is presented by an L-shaped (real) plane curve as a "divide knot" defined by N. A'Campo in the context of singularity theory of complex curves. For each knot given by Berge's parameters, the corresponding plane curve is constructed. The surgery coefficients are also considered. Such presentations support us to study each knot itself, and the relationship among the knots in the set of lens space surgeries.Comment: 26 pages, 19 figures. The proofs of Theorem 1.3 and Lemma 3.5 are written down by braid calculus. Section 4 (on the operation Adding squares) is revised and improved the most. Section 5 is adde

Milnor Numbers of Deformations of Semi-Quasi-Homogeneous Plane Curve Singularities

The aim of this paper is to show the possible Milnor numbers of deformations of semi-quasi-homogeneous isolated plane curve singularity f. Assuming that f is irreducible, one can write f=∑qα+pβ ≥ pqcαβ xαyβ where cp0c0q≠0, 2≤p<q and p, q are coprime. We show that as Milnor numbers of deformations of f one can attain all numbers from μ(f) to μ(f)−r(p−r), where q≡r(mod p). Moreover, we provide an algorithm which produces the desired deformations