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Talks and seminars, possibly part of a conference or series.

New guests at the MPIM

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Speaker: 
Margherita Lelli-Chiesa, Chul-hee Lee, Sergei Lanzat
Date: 
Thu, 2012-11-15 15:00 - 16:00
Location: 
MPIM Lecture Hall
Parent event: 
MPI-Oberseminar

No strict 3-groupoid models the 2-sphere

Posted in
Speaker: 
Daniel Brügmann
Date: 
Mon, 2012-11-12 10:15 - 12:00
Location: 
MPIM Lecture Hall

Section 4.4 or 4.3 in Simpson’s Book (ArXiv version).

Local Topological Field Theory and Fusion Categories, II

Posted in
Speaker: 
Noah Snyder
Affiliation: 
MPI
Date: 
Mon, 2012-11-12 17:30 - 18:15
Location: 
MPIM Lecture Hall
Parent event: 
Geometric Topology Seminar

Local Topological Field Theory and Fusion Categories

Posted in
Speaker: 
Noah Snyder
Affiliation: 
MPI
Date: 
Mon, 2012-11-12 16:30 - 17:15
Location: 
MPIM Lecture Hall
Parent event: 
Geometric Topology Seminar
Topological field theories give a close relationship between topology and
algebra.  Traditionally the main application has been from algebra to
topology: using algebraic constructions like quantum groups to produce
topological invariants.  However, you can also run the applications the
other way, using topology to arrange and clarify your knowledge about
algebra.  The goal of this talk is to explain one such application.

Darmon points: algorithms and numerical evidence

Posted in
Speaker: 
Xavier Guitart
Affiliation: 
Univ. Politécnica de Catalunya/MPI
Date: 
Thu, 2012-11-15 11:15 - 12:15
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar
Darmon points are a collection of conjectural generalizations of Heegner
points on modular elliptic curves. Algorithms for their effective
calculation are useful for gathering numerical evidence supporting their
conjectured properties. In addition, in some cases they can be used in
practice as very efficient methods for computing algebraic points in such
elliptic curves. In this talk I will recall two constructions of Darmon
points in different settings, and the algorithms of Darmon-Logan and
Darmon-Green-Pollack that allow for their computation in certain elliptic
curves.

Unipotent bundles

Posted in
Speaker: 
C. Kaiser
Date: 
Fri, 2012-11-09 10:15 - 11:45
Location: 
MPIM Seminar Room

IMPRS-seminar on Siegel's theorem on S-integral points on affine curves (following Kim)

Posted in
Date: 
Fri, 2012-11-09 10:15 - Fri, 2013-01-25 11:45
Location: 
MPIM Seminar Room

Algebraic approach to vortex moduli

Posted in
Speaker: 
Eduardo Gonzalez
Affiliation: 
U Massachusetts, Boston
Date: 
Tue, 2012-11-13 17:00 - 18:00
Parent event: 
Vortex Seminar

After a brief introduction to algebraic stacks, I will give an
overview of the algebraic version of the moduli space of vortices:
a stack of gauged maps with target X over C, where X is a projective
variety where a reductive group acts, and C a projective curve
where the vortices live. I will then introduce the notion of Mundet
semi-stability for gauged maps, and define gauged Gromov-Witten
invariants using this construction.

Bott periodicity

Posted in
Speaker: 
D. Radchenko
Date: 
Mon, 2012-11-12 10:15 - 11:45
Location: 
MPIM Seminar Room

Variation of GIT quotients and Wall-crossing in Gromov-Witten theory

Posted in
Speaker: 
Eduardo Gonzalez
Affiliation: 
HIM
Date: 
Tue, 2012-11-06 14:00 - 15:00
Location: 
MPIM Lecture Hall

Given an action of a reductive group $G$ on a smooth projective variety, Iwill give a wall
crossing formula that relates the Gromov Witten graph potentials of the GIT quotients
$X//G$ as we vary the polarisation, under suitable stable=semi-stable conditions.  
If time permits I will describe how to use this formula to show a version of the crepant
transformation conjecture of Li-Ruan, in the case when the trasformation comes from
variation of GIT. This is work with Chris Woodward.

Semi perfect obstruction theories and higher rank Donaldson-Thomas type invariants

Posted in
Speaker: 
Artan Sheshmani
Affiliation: 
MPI
Date: 
Tue, 2012-11-20 14:00 - 15:00
Location: 
MPIM Lecture Hall
We introduce a higher rank analog of the Pandharipande-Thomas theory of stable pairs on a
Calabi-Yau threefold $X$. More precisely, we develop a moduli theory for frozen triples
given by the data O^r---->F where "F" is a sheaf of pure dimension 1. The moduli space
of such objects does not naturally determine an enumerative theory: that is, it does not naturally

The tangent category of $C^\infty$-rings and a cosimplicial $C^\infty$-ring whose normalization is the De Rham complex

Posted in
Speaker: 
Herman Stel
Affiliation: 
Florence
Date: 
Wed, 2012-11-21 10:30 - 12:00
Location: 
MPIM Lecture Hall

Abundance of Morse functions and Lefschetz's hyperplane theorem

Posted in
Speaker: 
S. Schreieder
Date: 
Mon, 2012-11-05 10:15 - 11:45
Location: 
MPIM Seminar Room

Hyperbolic knot complements and commensurability, II

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Speaker: 
Neil Hoffman
Date: 
Mon, 2012-11-05 17:30 - 18:15
Location: 
MPIM Lecture Hall
Parent event: 
Geometric Topology Seminar
In second installment, I will talk about the recent progress toward proving the conjecture of Reid and Walsh that there are at most three hyperbolic knot complements in a given commensurability class. 

Hyperbolic knot complements and commensurability, I

Posted in
Speaker: 
Neil Hoffman
Date: 
Mon, 2012-11-05 16:30 - 17:15
Location: 
MPIM Lecture Hall
Parent event: 
Geometric Topology Seminar
Two manifolds are commensurable if they share a common finite sheered cover. Partitioning the set of hyperbolic 3-manifolds into commensurability classes organizes this set along similar geometric lines. However, however the general problem is quite difficult. Instead we will focus on a manifolds that appear rare in a commensurability class. In fact, Reid and Walsh conjecture that there are at most three hyperbolic knot complements in commensurability class. The first talk will focus on the background and motivation for this conjecture.

Generalized Khovanov (arc) algebra and applications in type D

Posted in
Speaker: 
Michael Ehrig
Affiliation: 
Mathematisches Institut, Uni. Bonn
Date: 
Mon, 2012-11-05 14:45 - 16:00
Location: 
MPIM Seminar Room

Metrics with large first eigenvalue

Posted in
Speaker: 
Alessandro Ghigi
Affiliation: 
Univ. Milano/MPI
Date: 
Thu, 2012-11-08 15:00 - 16:00
Location: 
MPIM Lecture Hall
Parent event: 
MPI-Oberseminar

I will start by recalling some basic facts on the first eigenvalue of
the Laplacian on a compact Riemannian manifold. Next I will discuss a
classical theorem of Hersch, which says that on the 2-sphere the first
eigenvalue is the largest possible when the metric is the standard
one.

I will then formulate the analogous problem for Kaehler metrics and
will describe the solution in the case of Hermitian symmetric
spaces of the compact type. If time permits I will try to explain the
link with Satake-Furstenberg compactifications and coadjoint orbits.

An introduction to DQ-modules

Posted in
Speaker: 
François Petit
Affiliation: 
MPIM
Date: 
Wed, 2012-10-31 10:30 - 12:00
Location: 
MPIM Lecture Hall

Incoherent Eisenstein series on U(n,n) and arithmetic geometry

Posted in
Speaker: 
Steve Kudla
Affiliation: 
University of Toronto
Date: 
Wed, 2012-11-07 14:15 - 15:15
Location: 
MPIM Lecture Hall
Parent event: 
Number theory lunch seminar
In this lecture, I will discuss the structure of the non-singular Fourier coefficients of
the derivative at the central critical point of incoherent Eisenstein series on U(n,n). 
In certain cases, these coefficients coincide with the arithmetic degrees of
0-cycles on moduli spaces of abelian varieties.  The proof of this relation depends
on p-adic uniformization and the determination of the structure of special cycles on
Rapoport-Zink spaces. 
This is joint work with Michael Rapoport.

2-groupoids and 2-types

Posted in
Speaker: 
Malte Pieper
Date: 
Mon, 2012-11-05 10:15 - 12:00
Location: 
MPIM Lecture Hall
  • Classification of 2-types and relation to
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