The Zariski problem concerns the analytical classification of germs of curves of the complex plane $\mathbb{C}^2$. In full generality, it is asked to understand as accurately as possible the quotient $\mathfrak{M}(f_0)$ of the topological class of the germ of curve $\lbrace f_0(x, y) = 0 \rbrace$ up to analytical equivalence relation. The aim of the talk is to review, as far as possible, the approach of Zariski as well as the recent developments. (Full abstract in attachment).

O. Zariski - analytic classification - foliation - germ - Puiseux expansion[-]

Let $(V,p)$ be a complex isolated complete intersection singularity germ (an ICIS). It is well-known that its Milnor number $\mu$ can be expressed as the difference:
$$\mu = (-1)^n ({\rm Ind}_{GSV}(v;V) - {\rm Ind}_{rad}(v;V)) \;,$$
where $v$ is a continuous vector field on $V$ with an isolated singularity at $p$, the first of these indices is the GSV index and the latter is the Schwartz (or radial) index. This is independent of the choice of $v$.
In this talk we will review how this formula extends to compact varieties with non-isolated singularities. This depends on two different ways of extending the notion of Chern classes to singular varieties. On elf these are the Fulton-Johnson classes, whose 0-degree term coincides with the total GSV-Index, while the others are the Schwartz-McPherson classes, whose 0-degree term is the total radial index, and it coincides with the Euler characteristic. This yields to the well known notion of Milnor classes, which extend the Milnor number. We will discuss some geometric facts about the Milnor classes.[-]

The Jacobian algebra, obtained from the ring of germs of functions modulo the partial derivatives of a function $f$ with an isolated singularity, has a non-degenerate bilinear form, Grothendieck Residue, for which multiplication by $f$ is a symmetric nilpotent operator. The vanishing cohomology of the Milnor Fibre has a bilinear form induced by cup product for which the nilpotent operator $N$, the logarithm of the unipotent part of the monodromy, is antisymmetric. Using the nilpotent operators we obtain primitive parts of the bilinear form and we compare both bilinear forms. In particular, over $\mathbb{R}$, we obtain signatures of these primitive forms, that we compare.[-]

Viehweg and Zuo obtained several results concerning the moduli number in smooth families of polarized varieties with semi-ample canonical class over a quasiprojective base. These results led Viehweg to conjecture that the base of a family of maximal variation is of log-general type, and the conjecture has been recently proved by Campana and Paun.
From the “opposite” side, Taji proved that a smooth projective family over a special (in the sense of Campana) quasiprojective base is isotrivial.
We extend Taji's theorem to quasismooth families, that is, families of leaves of compact foliations without singularities. This is a joint work with F. Campana[-]

I will explain how the recent developments in the theory of birational geometry of rank 2 foliations on 3-folds have find quite a few applications in the study of the structure of such foliations and their singularities.
In this talk that is a complement to the course of Cascini and Spicer, but which will be self-contained, I shall briefly explain why the MMP terminates and then proceed to illustrate a few applications of these techniques, e.g., to the classification of canonical singularities, to the study of adjunction theory, and to the study of hyperbolicity properties of foliated 3-folds.
The work is in collaboration with Calum Spicer.[-]