Arrangements of plane curves and related problems
16 (Mon) -- 18 (Wed) March, 2015.
Tokyo Metropolitan University, Mnami-Osawa Campus
(Room 610, 6F Bldg 8, (86K610)).
This workshop is supported by
JSPS Grants-in-Aid for Scientific Research 25610007 (Challenging Exploratory Research), JSPS-MAE Sakura Program
"Geometry and combinatorics of hyperplane arrangements and related topics" and
Reseach Grant (Tokyo Metro University).
Invited Speakers:
Schedule (Tentative)
16 (Mon) March 2015
10:00-11:00, Oka
11:15-12:15, Bailet
14:00-15:00, Libgober 1
15:15-16:15, Tokunaga
17 (Tue) March 2015
10:00-11:00, Abe
11:15-12:15, Bannai
14:00-15:00, Libgober 2
15:15-16:15, Callegaro
18 (Wed) March 2015
10:00-11:00, Settepanella
11:15-12:15, Yoshinaga
Abe
Title: Division free theorem for line arrangements and divisionally free
arrangements of hyperplanes
Abstract: The most useful method to show the freeness of line arrangements in
the projective space is Terao's addition-deletion theorems. First we
state a combinatorial formulation of them, i.e., a line arrangement is
free if its Poincare polynomial is divisible by that of its restriction. Starting
from this case, we propose a new class of free arrangements, called divisionally
free arrangements of hyperplanes. This class contains the calss of inductively
free arrangemetns, is strictly larger than it, and Terao's conjecture holds
in it.
Bailet
Title: Degeneration of Orlik-Solomon algebras and
Milnor fibers of complex line arrangements.
Abstract: PDF
Bannai
Title: Splitting curves of double coverings of the projective plane.
Abstract: In this talk, we study certain double coverings of the projective plane and splitting curves,
i.e., irreducible plane curves whose pre-images under the double-cover map become reducible.
We introduce the notion of a "splitting type" and apply it to study the topology of curve arrangements.
This is joint work with T. Shirane.
Callegaro
Title: Cohomology ring for toric arrangements
Abstract: The topic of this talk is the integer cohomology ring of the complement of a real complexified toric arrangement. We will recall some basic combinatorial invariants and we will show how these can help to give a presentation of the toric analogous of the Orlik-Solomon algebra. One of the main techniques involved is the Leray spectral sequence.
In the case of a non-unimodular arrangement, it is still an open problem to find
a suitable combinatorial object that can determine the integer cohomology ring. This is joint work with E. Delucchi.
Libgober (2 talks)
Title: Abelian varieties and plane algebraic curves I.
Abstract: The goal of these two talks is to discuss the
topological and Hodge theoretical invariants
associated with the complements to arrangements of plane algebraic curves.
In the first lecture I will focus on plane curves
with nodes, cusps or ADE
as the only singularities
and discuss the problems about Albanese varieties of
cyclic covers of plane ramified over singular curves.
One of the motivating problems is to find characterization of
the polynomials p(t) such that there exist plane algebraic
curve with Alexander polynomial p(t).
Part of the discussion is a description
of Mordell-Weil groups associated with plane singular
curves. Several examples are dealing with
arrangements of lines.
Title: Abelian Varieties and plane algebraic curves II
Abstract: I will discuss abelian varieties associated with
plane curves singularities and their role
in description of Albanese varieties of abelian covers associated
with plane curves and descriptions of pencils composed
of components of arrangements of plane curves. In many cases
one is lead to abelian varieties of CM type
appearing prominently in number theory.
No familiarity with abelian varieties will be assumed
in either of these talks. Part of material of these lecture
is based join papers with J.I.Cogolludo-Agustin and E.Artal-Bartolo.
Oka
Title: On the fundamental groups of non-generic $\mathbb{R}$-join-type curves.
Abstract: PDF
Settepanela
The nbc minimal complex of supersolvable arrangements
Abstract: PDF
Tokunaga
Title: Topology of plane curves of low degree via Galois covers and
rational elliptic surfaces
Abstract: We consider existence and non-existence of many Galois covers
at one time in order to study the topology of plane curves. It is rather
classical to make use of Galois covers to consider the topology of
plane curves, but our approach is new. In this talk, we show
that the approach is effective. Bisections of certain rational
elliptic surface play important roles to give explicit examples.
Yoshinaga
Title: Milnor fibers of real line arrangements.
Abstract: We give an algorithm computing monodromy eigenspaces
of the first cohomology of Milnor fibers of real line arrangements.
The algorithm is based on the description of minimal CW-complexes homotopic to the complements, and uses the real figure, that is, the adjacency relations of chambers. It enables us to generalize a vanishing result of Libgober, give new upper-bounds and characterize the A_3-arrangement in terms of non-triviality of Milnor monodromy.
Notice (7 Jan.):
The workshop will start in the morning 16th (Mon), the finall
talk will be around noon 18th (Wed).
We will have free discussion in the Wednesday afternoon.
Notice (14 Jan.):
Room has been changed. The new place is Room 610, 6F Bldg 8.
Notice (9 Feb.):
Titles and abstracts.
Organizers:
Hiro-o Tokunaga (tokunaga (at) tmu.ac.jp)
Masahiko Yoshinaga (yoshinaga (at) math.sci.hokudai.ac.jp)