We study properties of the signature function of the torus knot $T_{p,q}$.
First we provide a very elementary proof of the formula for the integral of the
signatures over the circle. We obtain also a closed formula for the
Tristram--Levine signature of a torus knot in terms of Dedekind sums.
We provide a very effective and explicit algorithm of finding a Puiseux
expansion of a cuspidal singularity of a plane curve, when this singularity is
given in a parametric form.
We use a knot invariant, namely the Tristram--Levine signature to study
deformations of singular points of plane curves. We find a bound on the sum of
M numbers over all singularities of a generic fiber in terms of the M number of
the singularity at the central fiber and some topological data.
We study deformations of plane curve singularities from an analytic point of
view and obtain some new concrete results. We show some rather unexpected
properties of Puiseux coefficients treated as functions on a suitably defined
parameter space. The methods used in paper are very elementary.
We bound the maximal number N of singular points of a plane algebraic curve C
that has precisely one place at infinity with one branch in terms of its first
Betti number $b_1(C)$. Asymptotically we prove that $N<\sim{17/11}b_1(C)$ for
large $b_1$. In particular, in the case of curves with one place at infinity,
we confirm the Zaidenberg and Lin conjecture stating that $N\le 2b_1+1$.