- Speaker: Ruth Kellerhals (University of Fribourg, OCAMI)
- Title: Some new developments on hyperbolic space forms in dimension 5
- Date: Mar. 21 (Wed.) 2012, 17：00〜18：00
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
After a short introduction to hyperbolic orbifolds, simple
constructions and properties, we consider those with many
symmetries and try to rank them by means of their volumes.
We discuss known results in dimensions below five and
present then new developments for hyperbolic 5-orbifolds
by restricting ourselves to the arithmetic, oriented case.
This is joint work with Vincent Emery (MPI Bonn).
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- Speaker:Hiroyuki OCHIAI (Institute of Mathematics for Industry, Kyushu University)
- Title:対称対の有限型２重旗多様体
- Date: Jan. 25 (Wed.) 2012, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
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- Speaker:Athanase Papadopoulos (Strasbourg University, France)
- Title:Teichmüller spaces of surfaces of infinite type
- Date: Dec. 7 (Wed.) 2011, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
I will describe some topological and metrical properties of Teichmüller spaces of surfaces of infinite type,
highlighting the differences with those of Teichmüller spaces of surfaces of finite type.
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- Speaker:Shigeaki KOIKE (Saitama University)
- Title:完全非線形方程式のABP最大値原理の最近の進展
- Date: Nov. 30 (Wed.) 2011, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
- Speaker:Megumi HARADA (McMaster University)
- Title:Finite group quotients among symplectic toric Deligne-Mumford stacks
- Date: Nov. 22 (Tue.) 2011, 17：00〜18：00
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:Let $\Delta$ be a Delzant polytope in $\mathbb{R}^n$. The
classical Delzant construction associates to $\Delta$ a compact
symplectic manifold equipped with an effective Hamiltonian
$T^n$-action, via a symplectic quotient construction. The
algebro-geometric analogue of this construction is the Cox
construction of toric varieties, where here the combinatorial input is
the data of a fan $\Sigma$ and uses a GIT quotient. These spaces which
are equipped with large torus actions provide a rich class of examples
in many areas of mathematics. More recently, Borisov-Chen-Smith
extended the Cox construction in the context of stack quotients, where
now the combinatorial input is a so-called stacky fan and the output
is the so-called toric Deligne-Mumford (DM) stack. The analogous
symplectic-geometric construction uses polytopes equipped with the
additional data of a labelling. As with their classical (non-stacky)
counterparts, toric DM stacks promise to be a fertile source of
examples on which to test general theories associated to stacks. In
this talk I will first quickly review these stacky constructions and
in particular relate the symplectic and algebro-geometric points of
view. Second, I will discuss joint work in progress with Krepski and
Goldin-Johannsen-Krepski which is motivated by the stack analogue of
the following classical topological question: when is a topological
space realizable as a quotient of a smooth manifold by a \emph{finite}
group action? In our context, at least in a special case, the answer
turns out to be quite concrete, explicit, and elegantly stated in
terms of the defining combinatorics.
- Speaker:Krzysztof Pawalowski (UAM, Poznan', Poland)
- Title:Smooth vs. symplectic actions on complex projective spaces
- Date: Nov. 17 (Thu.) 2011, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:The goal of the talk is to present a difference between arbitrary
smooth actions of compact Lie groups G on complex projective spaces
and these actions which preserve some additional structures on the
spaces, such as K\"ahler, symplectic, complex, or almost complex.
Our results show that in general the additional structures are not
preserved by smooth actions of G on complex projective spaces.
If an action of G preserves one of the additional structures above,
the fixed point set F is a manifold which admits the given structure.
We prove that the specific structure on F may be missing in general.
For an appropriate group G, it may even happen that any closed
smooth manifold F occurs as the fixed point set of a smooth action
of G on some complex projective space.
- Speaker:Atsushi KASUE (Kanazawa University)
- Title:無限ネットワークのランダムウォークと倉持境界
- Date: June 8 (Wed.) 2011, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
- Speaker:Yoshie SUGIYAMA (Osaka City University)
- Title:Keller-Segel系の解の構造について
- Date: Apr. 20 (Wed.) 2011, 16：30〜17：30
- Place: Dept. of Mathematics, Sci.Bldg., 3040
- Abstract:
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