講 演 者 |
:川見将広 (大阪市立大学数学研究所(OCAMI)) |
タ イ ト ル |
:Mod4 quadratic forms and diffeomorphisms on non-orientable surfaces |
|
(アブストラクト)
(PDF) |
日 時 |
:3月28日(金)15:00~16:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:秋吉宏尚 (大阪市立大学数学研究所) |
タ イ ト ル |
:Side parameter for the punctured torus groups |
|
(アブストラクト)
(PDF) |
日 時 |
:2月29日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:中村拓司 (大阪電気通信大学) |
タ イ ト ル |
:On knots of Delta unknotting number one from a view of the positivity
for knots |
|
(アブストラクト)
(PDF) |
日 時 |
:2月22日(金)16:30~17:30 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:Alexander Stoimenow (OCAMI, COE fellow) |
タ イ ト ル |
:Vassiliev invariants, Seifert matrix, and hyperbolic volume of knots |
|
(アブストラクト)
(PDF) |
日 時 |
:2月22日(金)15:30~16:30 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:森内 博正 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Classifications of theta-curves and handcuff graphs |
|
(アブストラクト)
(PDF) |
日 時 |
:2月8日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:Thomas Mattman (California State University) |
タ イ ト ル |
:Boundary Slope Diameter and Crossing Number of 2-Bridge Knots |
|
(アブストラクト)
(PDF) |
日 時 |
:2月1日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:金信 泰造 (大阪市立大学大学院理学研究科) |
タ イ ト ル |
:The sharp-unknotting number of a torus knot |
|
(アブストラクト)
(PDF) |
日 時 |
:12月14日(金)13:30~14:30 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:田山育男 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Enumerating 3-manifolds with lengths up to 9 by a canonical order
(joint work with Akio Kawauchi (Osaka City University)) |
|
(アブストラクト)
(PDF) |
日 時 |
:11月30日(金)15:30~16:30 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:Daniel Moskovich |
タ イ ト ル |
:Two Surgery Presentations for Dihedral Covering Spaces
(joint work with Andrew Kricker (Nanyang Technological University)) |
|
(アブストラクト)
(PDF) |
日 時 |
:11月30日(金)14:00~15:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:伊藤昇 (早稲田大学) |
タ イ ト ル |
:Invariants via word for curves |
|
(アブストラクト)
(PDF) |
日 時 |
:11月16日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:Yo'av Rieck (University of Arkansas) |
タ イ ト ル |
:On the Heegaard genus of knot exteriors
(joint with Tsuyoshi Kobayashi (Nara Women's University)) |
|
(アブストラクト)
(PDF) |
日 時 |
:11月9日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:門上晃久(大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Calculating the Casson-Walker invariants of cyclic branched coverings
over knots yielding lens spaces
(a joint work with Yasuyoshi Tsutsumi (Oshima National College of Maritime
Technology)
and Yukihiro Tsutsumi (Sophia University)) |
|
(アブストラクト)
(PDF) |
日 時 |
:10月12日(金)15:00~16:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:福本善洋(鳥取環境大学) |
タ イ ト ル |
:Homology spin cobordism problem of plumbed 3-manifolds and the cup product
structures |
|
(アブストラクト)
(PDF) |
日 時 |
:10月12日(金)14:00~15:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:佐藤隆夫 (大阪大学大学院理学研究科) |
タ イ ト ル |
:Twisted homology groups of the automorphism group of a free group |
|
(アブストラクト)
(PDF) |
日 時 |
:7月13日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:田中利史 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Maximal Thurston-Bennequin numbers and Rasmussen invariants of doubled
knots |
|
(アブストラクト)
(PDF) |
日 時 |
:7月6日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:牛島顕 (金沢大学大学院自然科学研究科) |
タ イ ト ル |
:Hyperbolic spatial graphs coming from strongly invertible knots
(joint work with Kazuhiro Ichihara (Nara University of Education)) |
|
(アブストラクト)
(PDF) |
日 時 |
:6月29日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:石井敦 (京都大学数理解析研究所) |
タ イ ト ル |
:The skein index for link invariants |
|
(アブストラクト)
(PDF) |
日 時 |
:6月15日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:佐藤進 (神戸大学大学院理学研究科) |
タ イ ト ル |
:The sheet numbers of 2-knots |
|
(アブストラクト)
(PDF) |
日 時 |
:6月8日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:岩切雅英 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Quandle cocycle invariants of charts with six white vertices |
|
(アブストラクト)
(PDF) |
日 時 |
:6月1日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:丹下 基生 (大阪大学大学院理学研究科) |
タ イ ト ル |
:タイトな接触構造とレンズ手術について |
|
(アブストラクト)
(PDF) |
日 時 |
:5月11日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:平澤 万希子 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:A classification of links up to 5-move equivalence |
|
(アブストラクト)
(PDF) |
日 時 |
:4月27日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:山本 亮介 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル |
:Complexity of open book decompositions via arc complex
(Joint work with Toshio Saito (Nara Women's University)) |
|
(アブストラクト)
(PDF) |
日 時 |
:4月20日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
講 演 者 |
:安井弘一 (大阪大学大学院理学研究科) |
タ イ ト ル |
:Small exotic rational surfaces without 1- and 3-handles |
|
(アブストラクト)
(PDF) |
日 時 |
:4月13日(金)16:00~17:00 |
場 所 |
:数学 第3セミナー室(3153) |
|
Top |
|
|
講 演 者: |
川見将広 (大阪市立大学数学研究所(OCAMI)) |
タ イ ト ル: |
Mod4 quadratic forms and diffeomorphisms on non-orientable surfaces |
We investigate Mod4 quadratic forms on the $\mathbb{Z}_{2}$-coefficient
first homology group of a non-orientable surface. In the case of the genus
of a surface is small, we can enumerate them up to isomorphims easily and
they are few. In this talk, we study the self-diffeomorphims on a non-orientable
surface which leave a given Mod4-quadratic form invariant.
講 演 者: |
秋吉宏尚 (大阪市立大学数学研究所) |
タ イ ト ル: |
Side parameter for the punctured torus groups |
The side parameter for the quasifuchsian punctured torus groups is defined
by Jorgensen in his famous unfinished paper on the combinatorial structures
of the Ford domains of such groups. The side parameter is a complete invariant
on the quasifuchsian space, and is extended to an invariant on the closure
of the space. The main results of this talk are the following:
1. The extended side parameter is also a complete invariant.
2. The composition of the inverse of the end invariant map and the side
parameter map is a self-homeomorphism on the common target space of the
invariants.
講 演 者: |
中村拓司 (大阪電気通信大学) |
タ イ ト ル: |
On knots of Delta unknotting number one from a view of the positivity for knots |
A Delta unknotting number for a knot is the minimal number of ``Delta moves"
needed to create the unknot. A knot is said to be positive if it has a
diagram whose all crossings are positive. In this talk, we show that a
Delta unknotting number one positive knot is the right-handed trefoil knot.
We also observe almost positive knots of Delta unknotting number one.
講 演 者: |
Alexander Stoimenow (OCAMI, COE fellow) |
タ イ ト ル: |
Vassiliev invariants, Seifert matrix, and hyperbolic volume of knots |
Given any knot K, we construct hyperbolic knots with arbitrarily large
volume, with the same Seifert matrix and the same Vassiliev invariants
of a bounded degree as K. An additional feature of our knots is that they
have bounded free genus.
講 演 者: |
森内 博正 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Classifications of theta-curves and handcuff graphs |
We have enumerated all the theta-curves and handcuff graphs with up to
seven crossings. To make a table of them, we need some spatial graph invariants.
In 1989, S. Yamada defined the topological invariant of spatial graphs
known as the Yamada polynomial. In this talk, we compute the Yamada polynomial
of some spatial graphs, and mention some properties of the Yamada polynomial.
講 演 者: |
Thomas Mattman (California State University) |
タ イ ト ル: |
Boundary Slope Diameter and Crossing Number of 2-Bridge Knots |
In joint work with Maybrun and Robinson, we prove that for 2-bridge knots,
the diameter of the set of boundary slopes is twice the crossing number.
After some topological preliminaries, the argument quickly becomes combinatorial
and is based on comparing various continued fraction representations of
the same fraction.
講 演 者: |
:金信 泰造 (大阪市立大学大学院理学研究科) |
タ イ ト ル: |
:The sharp-unknotting number of a torus knot |
The sharp-unknotting number was introduced by Hitoshi Murakami. He estimates
for the sharp-unknotting number from below using the signature, Arf invariant,
homology invariant from a cyclic covering. We give an estimation for the
sharp-unknotting numbers of torus knots, which determines for some cases.
講 演 者: |
田山育男 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Enumerating 3-manifolds with lengths up to 9 by a canonical order
(joint work with Akio Kawauchi (Osaka City University)) |
This is a joint work with A. Kawauchi. A well-order was introduced on the set of links by A. Kawauchi. This well-order also naturally induces a well-order on the set of prime link exteriors and eventually induces a well-order on the set of closed connected orientable $3$-manifolds. With respect to this order, we enumerated the prime links with lengths up to 10 and the prime link exteriors with lengths up to 9. In this talk, we show a list (with several pending manifolds) of the enumeration of $3-$manifolds with lengths up to 9 by using the enumeration of the prime link exteriors.
講 演 者: |
Daniel Moskovich |
タ イ ト ル: |
Two Surgery Presentations for Dihedral Covering Spaces
(joint work with Andrew Kricker (Nanyang Technological University)) |
This is joint work with A. Kricker. We present two different but related
procedures for obtaining surgery presentations of dihedral covering spaces
of $S3$ branched along knots. In particular we show that for any odd prime
p there are exactly p equivalence classes of p-coloured knots modulo surgery
by unit-framed (unknotted) components representing elements in the kernel
of the p-colouring.
講 演 者: |
伊藤昇 (早稲田大学) |
タ イ ト ル: |
Invariants via word for curves |
We construct an infinite sequence of invariants for curves in surfaces
by using word theory that V. Turaev introduced. For plane closed curves,
we add some extra terms, e.g. the rotation number. From these modified
invariants, we get the Arnold's basic invariants and some other invariants.
We also express how these invariants classify plane curves.
講 演 者: |
Yo'av Rieck (University of Arkansas) |
タ イ ト ル: |
On the Heegaard genus of knot exteriors
(joint with Tsuyoshi Kobayashi (Nara Women's University)) |
We will survey some of the authors' results about the behavior of Heegaard
genus of knot exteriors under connected sum operation. As our main result
we will prove that given integers $g_i > 1 (i=1,...,n)$, there exist
knots $K_i$ in $S3$ so that:
1) $g(E(K_i)) =g_i$, and:
2) $g(E(K_1\sharp ...\sharp K_n)) = g(E(K_1)) +...+ g(E(K_n))$.
This proves the existence of counterexamples to Morimoto's Conjecture.
講 演 者: |
門上晃久(大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Calculating the Casson-Walker invariants of cyclic branched coverings over knots yielding lens spaces
(a joint work with Yasuyoshi Tsutsumi (Oshima National College of Maritime
Technology)
and Yukihiro Tsutsumi (Sophia University)) |
We exhibit a technique for calculating concretely the Casson-Walker invariants
of cyclic branched coverings over knots yielding lens spaces on special
cases. By using it, we consider problems such as detecting problem of branched
covering spaces, and lens surgery problem in a homology 3-spheres.
講 演 者: |
福本善洋(鳥取環境大学) |
タ イ ト ル: |
Homology spin cobordism problem of plumbed 3-manifolds and the cup product
structures |
In this talk, we introduce two approaches to give necessary conditions
for abstract isomorphisms on homology of two plumbed 3-manifolds to be
realized by homology spin cobordisms geometrically. In the first approach
we use a V-manifold version of the Furuta-Kametani 10/8-inequality for
closed spin 4-manifolds to obtain a necessary condition in terms of an
integral lift of the Rochlin invariant and the quadruple cup product structure.
In particular, we formally calculate cup products by using the data of
abstract isomorphism on homology between plumbed 3-manifolds. In the second
approach we use the associativity of cup products. In fact, the formal
calculations of cup products may fail to satisfy the associativity law.
Motivated by this, we introduce a certain triple product to give other
necessary conditions.
講 演 者: |
佐藤隆夫 (大阪大学大学院理学研究科) |
タ イ ト ル: |
Twisted homology groups of the automorphism group of a free group |
In this talk, we compute twisted first and second homology groups of the automorphism group of a free group with coefficients in the abelianization of a free group and its dual group, using a presentation
sm group of a free group due to Gersten.
講 演 者: |
田中利史 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Maximal Thurston-Bennequin numbers and Rasmussen invariants of doubled knots |
Maximal Thurston-Bennequin number is a knot invariant from contact geometry.
It is well-known that the invariant is strictly less than the minimum v-degree
of the Kauffman polynomial in the framing variable v. Recently, we showed
that the Kauffman bound is sharp for any positive knot and any alternating
knot. However, it is known to be not sharp for many other knots in general.
In this talk, we confirm that the Kauffman bound is sharp for any double
of a knot if the bound is sharp for the knot. On the other hand, it is
also known that the maximal Thurston-Bennequin number is strictly less
than Rasmussen's s-invariant. We also discuss the s-invariant bound for
the maximal Thurston-Bennequin numbers of doubled knots.
講 演 者: |
牛島顕 (金沢大学大学院自然科学研究科) |
タ イ ト ル: |
Hyperbolic spatial graphs coming from strongly invertible knots
(joint work with Kazuhiro Ichihara (Nara University of Education)) |
There is a way, called "rational-fold cyclic branched covering,"
to construct spatial graphs from an invertible knot. In this talk we will
give a condition, which is expected to be a necessary and sufficient one,
for strongly invertible knots in the 3-sphere to yield hyperbolic spatial
graphs. We will also see that strongly invertible simple knots and tunnel
number one knots satisfy it so that we can have infinitely many hyperbolic
spatial graphs in the 3-sphere.
講 演 者: |
石井敦 (京都大学数理解析研究所) |
タ イ ト ル: |
The skein index for link invariants |
We introduce the skein index, which is an integer-valued index t is used
to compare link invariants and to find a skein relation. We give the complete
list for link invariants of skein index less than or equal to two, and
discuss the skein index of an operator invariant.
講 演 者: |
佐藤進 (神戸大学大学院理学研究科) |
タ イ ト ル: |
The sheet numbers of 2-knots |
A $2$-knot is an embedded $2$-sphere in $4$-space, and its diagram is a
projection image of the $2$-knot into $3$-space together with crossing
information. Such a diagram is regarded as a disjoint union of compact
connected surfaces each of which is called a sheet. The sheet number of
a $2$-knot is defined as the minimal number of sheets for all possible
diagrams of the $2$-knot. The notion of the sheet number is analogous to
the crossing number of a classical knot in $3$-space. In this talk, we
give a lower bound of the sheet number in several ways (Fox colorings,
fundamental quandles, and cocycle invariants), and determine the sheet
numbers of the $2$-, $3$-twist-spun trefoils, and some ribbon $2$-knots.
講 演 者: |
岩切雅英 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Quandle cocycle invariants of charts with six white vertices |
By $S_p(\Gamma)$, we denote the quandle cocycle invariant of a chart $\Gamma$
associated with Mochizuki's $3$-cocycle of the dihedral quandle of order
$p$. In this talk, we prove that there is no chart $\Gamma$ with six white
vertices such that $S_p(\Gamma)$ is non-trivial for some odd prime integer
$p$ but $3$. This gives lower bounds of the w-indices of some surface links.
We also consider charts with six white vertices such that $S_3(\Gamma)$
is non-trivial.
講 演 者: |
丹下 基生 (大阪大学大学院理学研究科) |
タ イ ト ル: |
タイトな接触構造とレンズ手術について |
レンズ空間を生む3次元球面の中の結び目のよく知られている制限とそれを満たす結び目を紹介する。
その制限を一般のホモロジー球面の場合に拡張し、そのホモロジー球面がL-spaceである場合にそれを満たす結び目の系列について述べる。 また3次元の接触構造を使って正の手術でレンズ空間を得ることができないホモロジー球面が存在することを示す。
講 演 者: |
平澤 万希子 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
A classification of links up to 5-move equivalence |
Montesinous and Nakanishi conjectured that 3-move and 4-move are unknotting
operations around 1980. In 2002, Dabkowski and Przytycki proved that 3-move
is not an unknotting operation via argument of Burnside group, but 4-move
conjecture remained unsettled. In this talk, we consider 5-move equivalence
relation, and classify rational links and links up to 9-crossings.
講 演 者: |
山本 亮介 (大阪市立大学数学研究所 OCAMI) |
タ イ ト ル: |
Complexity of open book decompositions via arc complex
(Joint work with Toshio Saito (Nara Women's University)) |
Based on Hempel's distance of a Heegaard splitting, we define a certain
kind of complexity of an open book decomposition, called a translation
distance, by using the arc complex of its fiber surface. We then show that
an open book decomposition is of translation distance at most two if it
is split into "simpler" open book decompositions and at most
three if it admits a Stallings twist on it.
講 演 者: |
安井弘一 (大阪大学大学院理学研究科) |
タ イ ト ル: |
Small exotic rational surfaces without 1- and 3-handles |
Jongil Park \textit{et al.}~constructed exotic $\mathbf{CP}^2\# n\overline{\mathbf{CP}}^2\,(5\leq
n\leq 8)$ by using rational blow-downs and elliptic fibrations. In this
talk we give another construction by using rational blow-downs and Kirby
calculus. We also prove our manifolds admit handle decompositions without
$1$- and $3$-handles, in the case $7\leq n\leq 9$. Note that every exotic
$\mathbf{CP}^2$, if it exists, has at least either a $1$- or $3$-handle
in each handle decompositon of it.
最終更新日: 2008年3月21日
(C)大阪市大数学教室
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