Abstracts:
KENNEDY'S TALK: The tangent star cone TS(X) of a scheme X is the normal
cone of the
diagonal in X-times-X; similarly one can define the relative tangent
star cone TS(X/T) of a morphism from X to T. Geometrically, TS(X)
consists of limiting secant lines to X, as the two points approach
each other. But TS(X) may also have a surprisingly intricate scheme
structure. Being cones, TS(X) and TS(X/T) carry Segre classes. Now
suppose that the Segre class s(TS(X/T)) specializes, over a point t
of T, to s(TS(Xt)), the Segre class of the fiber. Then, in certain
circumstances, one can show that TS(X/T) is flat over T above t.
SUWA'S TALK: Some of the important formulas in Complex
Analytic Geometry or Algebraic Geometry can be naturally interpreted as
``residue formulas", which are obtained by localizing certain
characteristic
classes of vector bundles or coherent sheaves.
This sort of theory
fits
nicely into the framework of the Cech-deRham cohomology. In fact, it
provides
not only a simple and natural way to prove the classical formulas but also
means
to deal with a wider range of problems such as the ones on singular
varieties or
singular foliations. The method is also effective for problems related to
characteristic classes in other areas including Symplectic Geometry. I
will try
to explain the underlying basic ideas and the essentials of some of the
following recent developements : 1) theory of Milnor classes for singular
varieties, 2) multiplicity of functions on singular varieties, 3)
Riemann-Roch
theorem for embeddings of singular varieties and its applications, 4)
simple
proof of the Lefschetz fixed point formula, 5) residues of singular
foliations
and its application to complex dynamical systems and 6) localization of
Maslov
classes.
BRASSELET'S TALK:
The Euler-Poincar'e characteristic is the first
example of a
characteristic class. It can be defined by
various ways, mainly
topological and geometrical ones. From the
Euler-Poincar'e characteristic
and through Poincar'e-Hopf theorem, we will pass
to obstruction theory.
Various examples will be given to show the
geometric point of view of the
theory.