過去の記録

2010年07月29日(木)

代数幾何学セミナー

14:30-16:00   数理科学研究科棟(駒場) 126号室
いつもと曜日・時間帯が異なります。ご注意ください。

Homological Mirror Symmetry for 2-dimensional toric Fano stacks (JAPANESE)
[ 講演概要 ]
Homological Mirror Symmetry (HMS for short) is a conjectural
duality between complex and symplectic geometry, originally proposed
for mirror pairs of Calabi-Yau manifolds and later extended to
Fano/Landau-Ginzburg mirrors (both due to Kontsevich, 1994 and 1998).

We explain how HMS is established in the case of 2-dimensional smooth
toric Fano stack X as an equivalence between the derived category of X
and the derived directed Fukaya category of its mirror Lefschetz
fibration W. This is related to Kontsevich-Soibelman's construction of
3d CY category from the quiver with potential.

We also obtain a local mirror extension following Seidel's suspension
theorem, that is, the local HMS for the canonical bundle K_X and the
double suspension W+uv. This talk is joint with Kazushi Ueda (Osaka
U.).

2010年07月28日(水)

GCOEセミナー

16:30-18:00   数理科学研究科棟(駒場) 002号室

[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

数値解析セミナー

16:30-18:00   数理科学研究科棟(駒場) 002号室

[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

2010年07月27日(火)

トポロジー火曜セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:00 - 16:30 コモンルーム

Quandle homology and complex volume
(Joint work with Yuichi Kabaya) (JAPANESE)
[ 講演概要 ]
For a hyperbolic 3-manifold M, the complex value (Vol(M) + i CS(M)) is called the complex volume of M. Here, Vol(M) denotes the volume of M, and CS(M) the Chern-Simons invariant of M.
In 2004, Neumann defined the extended Bloch group, and showed that there is an element of the extended Bloch group corresponding to a hyperbolic 3-manifold.
He further showed that we can compute the complex volume of the manifold by evaluating the element of the extended Bloch group.
To obtain an element of the extended Bloch group corresponding to a hyperbolic 3-manifold, we have to find an ideal triangulation of the manifold and to solve several equations.
On the other hand, we show that the element of the extended Bloch group corresponding to the exterior of a hyperbolic link is obtained from a quandle shadow coloring.
It means that we can compute the complex volume combinatorially from a link diagram.

博士論文発表会

16:00-17:15   数理科学研究科棟(駒場) 123号室

CM体のCM-typesとreflexの体のある代数的性質について (JAPANESE)

2010年07月22日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室
Owen Sizemore 氏 (UCLA)
$W^*$ Rigidity for actions of wreath product groups (ENGLISH)
[ 講演概要 ]
The past 8 years have seen much progress in the classification of
actions of groups on measure spaces. Much of this is due to new powerful
techniques in operator algebras. We will survey some of these results
as well as the new operator algebra techniques. We will then give new
results concerning the classification of actions of wreath product groups.

2010年07月20日(火)

トポロジー火曜セミナー

17:00-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:30 - 17:00 コモンルーム

A polynomial invariant of pseudo-Anosov maps (JAPANESE)
[ 講演概要 ]
Thurston-Nielsen classified surface homomorphism into three classes. Among them, the pseudo-Anosov class is the most interesting since there is strong connection to the hyperbolic manifolds. As an invariant, the dilatation number has been known. In this talk, I will introduce a new invariant of pseudo-Anosov maps. It is an integer coefficient polynomial, which contains the dilatation as the largest real root and is often reducible. I will show properties of the polynomials, examples, and some application to knot theory. (This is a joint work with Joan Birman and Peter Brinkmann.)

2010年07月15日(木)

Lie群論・表現論セミナー

14:30-16:00   数理科学研究科棟(駒場) 122号室
いつもと曜日、場所、開始時刻が異なります。
Soo Teck Lee 氏 (Singapore National University)
Pieri rule and Pieri algebras for the orthogonal groups (ENGLISH)
[ 講演概要 ]

The irreducible rational representations of the complex orthogonal
group $\\mathrm{O}_n$ are labeled by a certain set of Young diagrams,
and we denote the representation corresponding to the Young diagram
$D$ by $\\sigma^D_n$. Consider the tensor product
$\\sigma^D_n\\otimes\\sigma^E_n$ of two such representations. It can
be decomposed as
\$\\sigma^D_n\\otimes\\sigma^E_n=\\bigoplus_Fm_F\\sigma^F_n,\$
where for each Young diagram $F$ in the sum, $m_F$ is the
multiplicity of $\\sigma^F_n$ in $\\sigma^D_n\\otimes\\sigma^E_n$. In
the case when the Young diagram $E$ consists of only one row, a
description of the multiplicities in $\\sigma^D_n\\otimes\\sigma^E_n$
is called the {\\em Pieri Rule}. In this talk, I shall describe a
family of algebras whose structure encodes a generalization of the
Pieri Rule.

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室

Type II$_1$ von Neumann representations for Hecke operators on Maass forms (after F. Radulescu) (ENGLISH)

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 000号室

Mighty convergence in LAD type estimation (JAPANESE)
[ 講演概要 ]

[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/04.html

2010年07月13日(火)

トポロジー火曜セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:00 - 16:30 コモンルーム
Marion Moore 氏 (University of California, Davis)
High Distance Knots in closed 3-manifolds (ENGLISH)
[ 講演概要 ]
Let M be a closed 3-manifold with a given Heegaard splitting.
We show that after a single stabilization, some core of the
stabilized splitting has arbitrarily high distance with respect
to the splitting surface. This generalizes a result of Minsky,
Moriah, and Schleimer for knots in S^3. We also show that in the
complex of curves, handlebody sets are either coarsely distinct
or identical. We define the coarse mapping class group of a
Heeegaard splitting, and show that if (S,V,W) is a Heegaard
splitting of genus greater than or equal to 2, then the coarse
mapping class group of (S,V,W) is isomorphic to the mapping class
group of (S, V, W). This is joint work with Matt Rathbun.

解析学火曜セミナー

17:00-18:00   数理科学研究科棟(駒場) 128号室
Carlos Villegas Blas 氏 (メキシコ国立自治大学)
On a limiting eigenvalue distribution theorem for perturbations of the hydrogen atom (JAPANESE)
[ 講演概要 ]
Let H be the hydrogen atom Hamiltonian. We will show that
the operator H+P can have well defined clusters of eigenvalues
for a suitable perturbation P=f(h)Q where Q is a pseudo-differential
operator of order zero and f(h) is a small quantity depending of
the Planck's parameter h. We will show that the distribution of
eigenvalues in those clusters has a semi-classical limit involving
the averages of the principal symbol of Q along the classical orbits
of the Kepler problem.

2010年07月12日(月)

複素解析幾何セミナー

10:30-12:00   数理科学研究科棟(駒場) 128号室

[ 講演概要 ]

代数幾何学セミナー

16:40-18:10   数理科学研究科棟(駒場) 126号室

Flips of moduli of stable torsion free sheaves with $c_1=1$ on
$\\\\mathbb{P}^2$ (JAPANESE)
[ 講演概要 ]
We study flips of moduli schemes of stable torsion free sheaves
on the projective plane via wall-crossing phenomena of Bridgeland stability.
They are described as stratified Grassmann bundles by variation of
stability of modules over certain finite dimensional algebra.

2010年07月08日(木)

応用解析セミナー

16:00-17:30   数理科学研究科棟(駒場) 002号室
Anna Vainchtein 氏 (University of Pittsburgh, Department of Mathematics)
Effect of nonlinearity on the steady motion of a twinning dislocation (ENGLISH)
[ 講演概要 ]
We consider the steady motion of a twinning dislocation in a Frenkel-Kontorova lattice with a double-well substrate potential that has a non-degenerate spinodal region. Semi-analytical traveling wave solutions are constructed for the piecewise quadratic potential, and their stability and further effects of nonlinearity are investigated numerically. We show that the width of the spinodal region and the nonlinearity of the potential have a significant effect on the dislocation kinetics, resulting in stable steady motion in some low-velocity intervals and lower propagation stress. We also conjecture that a stable steady propagation must correspond to an increasing portion of the kinetic relation between the applied stress and dislocation velocity.

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
Dave Penneys 氏 (UC Berkeley)
Killing weeds with annular multiplicities $*10$ via quadratic tangles (ENGLISH)
[ 講演概要 ]
In recent work with Morrison, Peters, and Snyder, we eliminate two
families of possible principal graphs with graph norms less than 5 using
techniques derived from Jones' work on quadratic tangles.

2010年07月07日(水)

諸分野のための数学研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室

[ 講演概要 ]

また,ステップが一方向を向いて階段状になっている微斜面と呼ばれる結晶表面が現れる場合がしばしばある。

GCOEセミナー

17:00-18:00   数理科学研究科棟(駒場) 002号室

[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

数値解析セミナー

17:00-18:00   数理科学研究科棟(駒場) 002号室
いつもと時間帯が異なりますので御注意下さい。

[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 056号室

On the stable reduction of $X_0(p^4)$ (JAPANESE)

2010年07月06日(火)

トポロジー火曜セミナー

17:00-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:40 - 17:00 コモンルーム

On the cohomology of free and twisted loop spaces (JAPANESE)
[ 講演概要 ]
A natural extension of cohomology suspension to a free loop space is
constructed from the evaluation map and is shown to have a good
properties in cohomology calculation. This map is generalized to a
twisted loop space.
As an application, the cohomology of free and twisted loop space of
classifying spaces of compact Lie groups, including certain finite
Chevalley groups is calculated.

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 118号室
Robert Sims 氏 (Univ. Arizona)
On the Existence of the Dynamics for Anharmonic Quantum Oscillator Systems (ENGLISH)

2010年07月05日(月)

複素解析幾何セミナー

10:30-12:00   数理科学研究科棟(駒場) 128号室

[ 講演概要 ]

代数幾何学セミナー

16:40-18:10   数理科学研究科棟(駒場) 126号室

Rational curves on hypersurfaces (JAPANESE)
[ 講演概要 ]
Our purpose is to study the family of smooth rational curves of degree $e$ lying on a hypersurface of degree $d$ in $\\mathbb{P}^n$, and to investigate properties of this family (e.g., dimension, smoothness, connectedness).
Our starting point is the research about the family of lines (i.e., $e = 1$), which was studied by W. Barth and A. Van de Ven over $\\mathbb{C}$, and by J. Koll\\'{a}r over an algebraically closed field of arbitrary characteristic.
For the degree $e > 1$, the family of rational curves was studied by J. Harris, M. Roth, and J. Starr over $\\mathbb{C}$ in the case of $d < (n+1)/2$.
In this talk, we study the family of rational curves in arbitrary characteristic under the assumption $e = 2,3$ and $d > 1$, or $e > 3$ and $d > 2e-4$.

2010年07月02日(金)

談話会・数理科学講演会

16:30-17:30   数理科学研究科棟(駒場) 123号室
お茶&Coffee&お菓子: 16:00～16:30 (コモンルーム)。

[ 講演概要 ]