This is the seventh workshop that we are organizing. These mini-workshops take place biannually. The goal is to strengthen the symplectic community of the Netherlands and to connect it with abroad. Topics include Hamiltonian dynamics, the symplectic embedding question, holomorphic curves, and Floer homology.

* If you are interested in participating then please register.

Dietmar Salamon (ETH Zürich)

Agnès Gadbled (Uppsala University)

Michael Entov (Technion Haifa)

Darko Milinković (University of Belgrade)

Oliver Fabert (Vrije Universiteit Amsterdam)

Fabian Ziltener (Universiteit Utrecht)

**Speakers**

Javier Fresán (ETH, Zurich)

Michael Groechenig (FU, Berlin)

Johannes Nicaise (Imperial College/Leuven)

The first lecture starts at 13:00h. For further information, titles and abstracts, see the seminar website.

**Organizers:** Johannes Nicaise (Imperial College/Leuven), Nero Budur (Leuven), Lenny Taelman (Amsterdam), Bas Edixhoven (Leiden), Arne Smeets and Ben Moonen (Nijmegen),

Examples will be provided in the second part of the talk.

Dates: Wednesdays 11 and 18 October

]]>Examples will be provided in the second part of the talk.

Date and time: Wednesday 11 and 18 October 14-15 h

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Some information can be found on the web page

http://www.projects.science.uu.nl/Moerdijk/HigherLower%202017%20home%202.htm

where more details will appear in due course. You are welcome to attend the lectures. But please register on that web page if you do, so that we (and the catering!) have an idea of the number of participants.

]]>This is the sixth workshop that we are organizing. These mini-workshops take place biannually. The goal is to strengthen the symplectic community of the Netherlands and to connect it with abroad. Topics include Hamiltonian dynamics, the symplectic embedding question, holomorphic curves, and Floer homology.

* If you are interested in participating then please register.

Kaoru Ono (Kyoto)

Sergei Kuksin (Paris 7)

Peter Albers (Heidelberg)

Alberto Abbondandolo (Bochum)

Oliver Fabert (Vrije Universiteit Amsterdam)

Fabian Ziltener (Universiteit Utrecht)

Tuesday the 17th and Wednesday the 18th of December on the occasion of Qizheng Yin’s defence of his doctors thesis.

The defence will be on the Wednesday.

**Speakers (December 17th)**

Gerard van der Geer (Amsterdam)

Dan Petersen (Zürich)

Arnaud Beauville (Nice)

Qizheng Yin (Nijmegen)

**Speakers (December 18th)**

Lenny Taelman (Leiden)

Claire Voisin (École Polytechnique)

Sergey Shadrin (Amsterdam)

**Belgian-Dutch Algebraic Geometry Day
**

**Venue**

The lectures are given in the Huygens Building, room HG00.071 on the ground floor.

Address: Heyendaalseweg 135, Nijmegen.

**Programme**

13:00-14:00 Nero Budur (Leuven) TBA

14:00-14:30 Coffee break

14:30-15:30 Stefan Schröer (Düsseldorf) TBA

15:30-16:00 Coffee break

16:00-17:00 René Schoof (Rome) TBA

As usual, after the lectures we intend to go for an informal dinner in town.

**Workshop on Foliations and Orbispaces, 21-22 November
**

**Description**

The focus of this short workshop lies on (possibly singular) foliations are their leaf spaces, both from a classical perspective (\Gamma-structures, Riemannian foliations,..) and a modern one (Lie groupoids).

**Speakers**

Gael Meignez (Bretagne-Sud)

Marcos Alexandrino (Sao Paulo)

Hessel Posthuma (Amsterdam)

Matias del Hoyo (Utrecht)

Marco Zambon (Madrid)

**Higher Geometric Structures along the Lower Rhine III
**

This is the third in a series of short workshops jointly organized by the Geometry/Topology groups in Bonn, Nijmegen, and Utrecht, all situated along the Lower Rhine. The focus lies on the development and application of new structures in geometry and topology such as Lie groupoids, differentiable stacks, Lie algebroids, generalized complex geometry, topological quantum field theories, higher categories, homotopy algebraic structures, higher operads, derived categories, and related topics. The first workshop took place in Bonn and the second in Nijmegen.

**Speakers **

Camilo Arias Abad (Bonn)

Javier Gutiérrez (Nijmegen)

Matias del Hoyo (Utrecht)

Arturo Prat-Waldron (Bonn)

Gregor Schaumann (Universität Erlangen-Nürnberg)

Pavol Ševera (Université de Genève)

Anton Zeitlin (Columbia University)

**Workshop Noncommutative Geometry and Particle Physics, Leiden\
**

Lorentz Center Leiden, October 14-18, 2013.

**Topics:**

- The Higgs Sector and its Experimental Status
- Phenomenology of Electroweak and Strong Forces
- The Noncommutative Standard Model
- Particle Physics: Beyond the Standard Model
- Family Structure of Particle Physics
- Gravity and Noncommutative Geometry

**Scientific organizers:**

- Thijs Van den Broek (Nijmegen, The Netherlands)
- Alain Connes (Bures-sur-Yvette, France)
- Jose Gracia-Bondia (Zaragoza, Spain)
- Piet Mulders (Amsterdam, The Netherlands)
- Walter Van Suijlekom (Nijmegen, The Netherlands)

**Workshop Knots & Physics, Amsterdam
**

**Speakers:**

Gaetan Borot (MPI Bonn),

Jinseok Cho (KIAS Seoul),

Sebas Eliens (ITF Amsterdam),

Hitoshi Murakami (Tohoku University),

Satoshi Nawata (NIKHEF Amsterdam).

**Organisers:** Satoshi Nawata and Roland van der Veen

**Workshop “Elliptic Integrable Systems and Hypergeometric Functions”
**

5 day workshop from July 15th – 19th, 2013. Scientific organizers: Erik Koelink, Masatoshi Noumi, Eric Rains, Hjalmar Rosengren, Simon Ruijsenaars, Jasper Stokman.

**A singular life – Conference in honour of Eduard Looijenga
**

This two-day conference (27 & 28 of June) marks the retirement of Professor Eduard Looijenga and will be a celebration of his achievements and influence in Dutch and International mathematics. The confirmed speakers are Arnaud Beauville (Laboratoire J.-A. Dieudonn�, Nice), Igor Dolgachev (University of Michingan), Carel Faber (Royal Institute of Technology, Stockholm), Gerard van der Geer (University of Amsterdam), Gert Heckman (Radboud Universiteit Nijmegen), Joseph Steenbrink (Radboud Universiteit Nijmegen), Jonathan Wahl (University of North Carolina), Shing-Tung Yau (Harvard University) Don Zagier (Max Planck Institute — Bonn)

**G&T day – Utrecht
**

The Quarterly seminar on Topology and Geometry aims to take place every bimester in the mathematics department in Utrecht. Our next meeting will happen on the 21st of June 2013 in MIN 211.

The speakers will be Jonny Evans, Igor Khavkine and James Tener.

**Mini Workshop on locally analytic representations and some applications
**

June 5-6, 2013, at Vrije Universiteit Amsterdam

supported by the DIAMANT cluster*

**Organizers:** Deepam Patel (VU Amsterdam), Tobias Schmidt (Munster), Matthias Strauch (Indiana)

* funded by the Netherlands Organisation for Scientific Research (NWO), the Ministry of Education, Culture and Science (OCW), and the Ministry of Economic Affairs (EZ).

**Topology & Geometry Day on the occasion of Maria Amelia Salazar’s Ph.D. defense
**

**GQT colloquium Utrecht
**

Place: Universiteit Utrecht; Minnaert Building, room 208.

Schedule: 13:00 to 14:00 – Kim Froyshov (Aarhus): On the existence of representations of finitely presented groups in compact Lie groups;

14:00 to 14:30 – Coffee;

14:30 to 15:30 – Moritz Groth (Nijmegen): Some first steps with Grothendieck derivators;

15:45 to 16:45 – Matthias Kreck (Hausdorff Institute): Special codes – special manifolds?

**Workshop “Moduli of curves and integrable hierarchies”
**

On the occasion of the thesis defense of Alexandr Buryak, a workshop takes place on Friday, April 26 at the University of Amsterdam (Plantage Muidergracht 24, 1018 TV Amsterdam, N.B.: This is OLD LOCATION of the KdV Institute). The lecture room is P0.14.

The **program** is as follows:

13:15-14:15 Maxim Kazarian (Moscow): Topological recursion for the genus zero descendant Hurwitz potential.

14:15-14:45 Coffee and tee.

14:45-15:45 Johan van de Leur (Utrecht): Hirota equations for the extended bigraded Toda hierarchy and the total descendant potential of CP^1 orbifolds.

16:00-17:00 Dimitri Zvonkine (Paris): A (complete?) family of relations between tautological cohomology classes of Mbar_{g,n}

**Abstract Kazarian:**

Double Hurwitz numbers enumerate possible ways to represent the identical permutation as the product of two permutations of given cyclic types and a given number of transpositions. In topological terms, they describe topologically distinct meromorphic functions on Riemann surfaces of given genus with prescribed critical values and prescribed orders of poles and zeroes. These numbers themselves are well studied and there are known formulas for their generating function. In spite of the existence of such formulas and a variety of modern proofs, many natural questions concerning these numbers remain open.

We propose a new recursion for these numbers that has a topological origin: it is derived from cohomological information contained in the stratification of the Hurwitz space by multisingularities of the functions. We expect that variations of this approach could be adopted to other families of Hurwitz numbers for which closed formulas are not known at the moment, including those for curves of higher genera.

(Joint work with S.Lando and D.Zvonkine)

**Abstract van de Leur:**

Milanov and Tseng conjectured that the total descendent potential of the orbifold C_{k;m} is a tau function of the extended bigraded Toda hierarchy. We prove this conjecture.

(Joined work with Guido Carlet)

**Abstract Zvonkine:**

Let M_g be the moduli space of smooth curves of genus g. As g tends to infinity, the cohomology ring of M_g stabilizes to Q[kappa_1, kappa_2, …] for certain natural cohomology classes kappa_m. For a fixed g, however, there are polynomial relations between the kappa-classes. The study of these relations was started by C. Faber in 1993 and is still not finished 20 years later.

We can complicate the problem by adding marked points and passing to the Deligne-Mumford compactification of the moduli space, which greatly increases the number of generators and relations. We will construct a family of relations between these generators that contains all known relations and, conjecturally, all existing relations. The construction involves r-spin structures (r-spin = r-th root of the cotangent line bundle to the curve) and Frobenius manifolds.

(Joint work with A. Pixton et R. Pandharipande)

The defence of Alexandr Buryak will take place on 10:00 at the Agnietenkapel (Oudezijds Voorburgwal 229-231, 1012 EZ Amsterdam). Title of the thesis: “Topology of the moduli space of curves and integrable hierarchies”.

Everybody is welcome!

**Operations on Hochschild complexes, revisited
**

**Speaker:** Boris Tsygan (Northwestern University)

**Date and time:** Thursday, March 28th, 2013 from 16:00-17:00hrs

**Location:** UVA, Science Park 904, Room A1.06

**Title:** Operations on Hochschild complexes, revisited.

**Abstract:** Algebraic structures on Hochschild cochain and chain complexes of algebras are long known to be of considerable interest. On the one hand, some of them arise as standard operations in homological algebra. On the other hand, for the ring of functions on a manifold, Hochschild homology, resp. cohomology, is isomorphic to the space of differential forms, resp. multivector fields, and many algebraic structures from classical calculus can be defined (in a highly nontrivial way) in a more general setting of an arbitrary algebra and its Hochschild complexes. Despite an extensive amount of work on the subject, it appears that large parts of the algebraic structure on the Hochschild complexes of algebras and their tensor products are still unknown. I will review the known results (Kontsevich-Soibelman, Dolgushev, Tamarkin and myself, Keller) and then outline some provisional results and conjectures about new operations. The talk will not assume any prior knowledge beyond basic facts about complexes and (co)homology.

**GQT colloquium Nijmegen
**

**place:** Radboud Universiteit Nijmegen, Huygensgebouw

**time:** 13:00 – 17:00

**room:** HG00.108

**program:**

13:00 – 14:00 **Christian Voigt **(University of Glasgow)

**The string group and vertex algebras **

The string group String(n) is an infinite dimensional analogue of the spin group Spin(n) familiar from geometry and index theory. In this talk I will discuss a tentative realisation of String(n) using unitary vertex superalgebras and field algebras. This includes a categorified analogue of the Clifford algebra and its spinor representation, and I will explain carefully the analogy to the situation for the spin group.

14:30 – 15:30 **Simon Salamon **(King’s College London)

**Surveying points in the complex projective plane **

I shall introduce Zauner’s conjecture on the existence of SIC-POVM’s (symmetric informationally complete positive operator valued measures, that correspond to n^2 equidistant points in CP^(n-1) with the Fubini-Study metric). The theory will be illustrated in only the simplest situations of n=3 and 4, but from a geometer’s perspective using the concept of moment mapping.

16:00 – 17:00 **Raf Bocklandt **(Universiteit van Amsterdam)

**Noncommutative mirror symmetry for punctured surfaces **

A dimer model on a surface with punctures is an oriented graph such that its nodes correspond to the punctures and the arrows circle round the faces they cut out. To any dimer model Q we can associate 2 categories: A wrapped Fukaya category F(Q) and a category of matrix factorizations M(Q).

In both categories the objects are arrows, which are interpreted as Lagrangian subvarieties in F(Q) and will give us certain matrix factorizations of a potential on the Jacobi algebra of the dimer in M(Q).

We show that there is a duality D on the set of all dimers such that for consistent dimers the category of matrix factorizations M(Q) is isomorphic to the Fukaya category of its dual, F(D(Q)). We also discuss the connection between classical mirror symmetry.

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**15.00:** Tea

**15.30-16.30:** Colloquium Lecture, Pangea Lecture Theater, Koningberger building

**16.30:** Drinks in the Library

Two more seminar lectures by Professor Madsen from **11.00-12.00** and **15.00-16.00** in the **Hans Freudenthal Building **, room 611

We would like to announce the ninth workshop of the series on “Higher Geometric Structures along the Lower Rhine”, jointly organized by geometers and topologists from Bonn, Nijmegen, and Utrecht.

The meeting will be held at Radboud University Nijmegen, on May 11-12, 2017.

The focus of this workshop series lies on the development and application of new structures in geometry and topology such as Lie groupoids, differentiable stacks, Lie algebroids, generalized complex geometry, topological quantum field theories, higher categories, homotopy algebraic structures, higher operads, derived categories, and related topics.

The speakers are:

Francesca Arici

Michael Bailey

Tyrone Crisp

Honglei Lang

Milena Pabiniak

Markus Pflaum

For the registration and more information please check site.

**Topology/geometry seminar: Ezra Getzler will give a talk on The derived Maurer-Cartan locus**

**Abstract:** This talk is based on a recent paper in l’Enseignement Mathématique of this title. There are two models for derived schemes: differential graded manifolds and cosimplicial manifolds. The cosimplicial formalism is more general: in this talk, I construct a functor from differential graded Lie algebras to cosimplicial manifolds which represents the derived Maurer-Cartan locus. The talk will be a very gentle introduction to this subject: some background in the theory of simplicial and cosimplicial abelian groups is useful but not required.

As always, all interested are welcome.

Ieke Moerdijk

**Workshop on generalized geometry
**

We are organizing a mini workshop on the occasion of Joey van der Leer Duran’s graduation. The meeting will take place in the Sonnenborgh Observatorium on the 30th of November. The speakers will be Gueo Grantcharov, Ioan Marcut and Brent Pym.

Registration is free and people attending the workshop will be provided with coffee and lunch. To help us with the planning, please register if you intend to come.

**GQT school and colloquium
**

Will take place in Ernst Sillem Hoeve Hotel and Conference Center form the 28th of November to the 2nd of December.

School lectures will be:

Martijn Kool — Toric varieties and equivariant vector bundles

Suijlekom & Arici — Noncommutative geometry and gauge theories

Gerard van der Geer — Modular forms

See the event webpage for registration and further details.

**Workshop: The Big Picture (on the occasion of Jan Stienstra’s retirement)
**

**Date:** Friday November 25, 2016 (10.30-17.30).

**Speakers:**

Raf Bocklandt (UvA)

Vasily Golyshev (Moscow)

Anton Mellit (Trieste)

Duco van Straten (Mainz)

**Registration:
**Participation in this symposium is open and free to all interested, but registration is required. Please register by sending an email to science.secr.mathins@uu.nl as soon as possible. Mention in this email “JS65”. Lunch (Yes or No; Also, if you have special dietary requirements, please let us know). For more information click on the link above.

**Mini-workshop on symplectic geometry
**

On September 30 we will organize a mini-workshop on symplectic geometry at the VU Amsterdam. It is aimed at researchers, Ph.D. students, and advanced master’s students working in symplectic geometry and related areas. The speakers are:

Hansjörg Geiges (Universität zu Köln)

Urs Frauenfelder (Universität Augsburg)

Alexander Ritter (University of Oxford)

Lev Buhovski (Tel Aviv University)

* If you are interested in participating then please register.

Please indicate if you will join us for dinner.

organizers:

Oliver Fabert (VU Amsterdam)

Fabian Ziltener (Universiteit Utrecht)

**GQT School and Colloquium
**

The next GQT school and colloquium will take place in Woudschoten Hotel and Conference Center form the 6th to 10th of June. School lectures will be:

Ioan Marcut — Dirac Structures

Gert Heckman — Complex reflexion groups

Nicolai Reshetikhin — BV-quantization

See the event webpage for registration and further details.

**2nd Kan memorial lectures
**

We are honoured that Graeme Segal (Oxford) will give the 2nd Kan Memorial Lectures at Utrecht University.

The lectures start with a colloquium style talk on 2 June, in the

**The Ubiquity of Homotopy, **15.30-16.30

Refreshments beforehand from 15.00-15.30

Drinks afterwards from 16.30-17.00 in the mathematics library

Two more specialised lectures will follow on

Friday 3 June, in The **Hans Freudenthal building, room 611**

**Aspects of non-commutative geometry, **11.00-12.00

**Higher structures in homotopy theory, **15.00-16.00

**Abstract**

Much of mathematics is about discovering robust kinds of structure which organize and illuminate large areas of the subject. Perhaps the most basic organizing concept of our thought is space. It leads us to the homotopy category, which captures many of our geometric intuitions but also arises unexpectedly in contexts far from ordinary spaces. Still more is this true of the `stable homotopy’ category, which sits midway between geometry and algebra.

The theme of my lectures is the strangeness and the ubiquity of the homotopy and stable homotopy categories, and how they give us new ideas of what a space is, and why manifolds and spaces with algebraic structure play such a special role. The first lecture will be a non-technical survey of things discussed in more detail in the following two, such as the dual ways of thinking of a space in terms of the paths in it and in terms of its algebra of functions; also, what abstract homotopy theory is, and how it leads us to new geometrical ideas and new analogues of the stable homotopy category.

One of the biggest steps in disengaging homotopy from spaces was Kan’s theory of simplicial objects; a subtheme is the different ways in which this can be viewed and the different directions in which it can lead.

The second lecture focuses on the relation between spaces and their algebras of functions, algebraic K-theory, and the nature of noncommutative spaces and `quantization’ – what it means for a noncommutative object to be a deformation of a normal space. We see how the stable homotopy category sits inside a noncommutative stable category. I shall speculate on the place of Floer homotopy theory in this picture.

The third lecture is partly about how manifolds relate to stable homotopy, and the role of Poincare duality and quadratic forms. It is also about the `higher homotopies’ which lie below the surface of the naive homotopy category. This is another angle on the interpolation between commutativity and noncommutativity, more from the perspective of traditional algebraic topology.

**Topics in the Langlands Correspondence**

Workshop on June 2nd and 3rd at the University of Amsterdam, Kortweg de Vries Institute on the occasion of the Ph.D. defense of Marcelo G. De Martino

**Location** SP 107, room F3.20

**Programme**

**Thursday 02/06**

**15:00-16:00:** Gordan Savin (University of Utah)

**16:15-17:15:** Erik van den Ban (Universiteit Utrecht)

**Friday 03/06**

**10:00-11:00:** Dipendra Prasad (Tata Inst. of Fund. Research)

**11:15-12:15:** Anne-Marie Aubert (Inst. Mathématiques de Jussieu)

Gordan Savin: TBA

Erik van den Ban: TBA

**Dipendra Prasad:** *A relative Local Langlands correspondence.*

**Abstract:** For E/F quadratic extension of local fields, we consider the question of classifying irreducible admissible representations of G(E) which carry a G(F)-inv. linear form. Although in a certain generic sense, one expects a simple answer – multiplicity 1, and exact characterization, the full answer is rather complicated – and interesting, involving geometry of Langlands parameters.

**Anne-Marie Aubert:** *Cuspidality and Hecke algebras for enhanced Langlands parameters*

**Abstract:** Enhanced Langlands parameters for a p-adic group G are pairs formed by a Langlands parameter for G and an irreducible character of a certain component group attached to the parameter. We will introduce a notion of cuspidality for these pairs, describe a construction of a cuspidal support map for enhanced Langlands parameters, and attach an almost affine Hecke algebra to every cuspidal support. It is joint work with Ahmed Moussaoui and Maarten Solleveld.

**Belgian-Dutch Algebraic Geometry Day
**

Friday April 22 in Leuven: 10th edition of the Belgian-Dutch Algebraic Geometry Days. Speakers: Sho Tanimoto (Copenhagen), John Christian Ottem (Oslo), Bruno Chiarellotto (Padova).

**Gauge Theory and Noncommutative Geometry
**

4-8 April 2016 at the Radboud University Nijmegen.

More details can be found **here**

If you’re interested in coming, please let us know by filling in the registration form.

**Organizing committee**

Simon Brain

Klaas Landsman

Walter van Suijlekom

**Mini-Workshop on Symplectic Geometry
**March 11th, 2016

This mini-workshop is aimed at researchers, Ph.D. students, and advanced master’s students working in symplectic geometry and related areas. It is organized jointly with the Vrije Universiteit Amsterdam.

This is the third workshop that we are organizing. These mini-workshops take place biannually. The goal is to strengthen the symplectic community of the Netherlands and to connect it with abroad. Topics include Hamiltonian dynamics, the symplectic embedding question, holomorphic curves, and Floer homology.

**Speakers**

Claude Viterbo (ENS Paris)

Janko Latschev (Universität Hamburg)

Yaron Ostrover (Tel Aviv University)

Chris Wendl (University College London)

**Organizers**

Oliver Fabert (Vrije Universiteit Amsterdam)

Fabian Ziltener (Universiteit Utrecht)

Please **register**by March 3!

For any question please contact Oliver Fabert at o.fabert@vu.nl and Fabian Ziltener at f.ziltener@uu.nl .

**Winter school: Banach methods in noncommutative geometry
**

From 25th-29th January, 2016 we have organized a winter school in Münster entitled *Banach methods in noncommutative geometry: isomorphism conjectures and geometry of groups.* The school is aimed at PhD students and postdocs as well as M.Sc. students continuing in academia. We will focus on the connection between Banach/operator space methods as approximation properties and geometric properties of groups and their connection to problems as the Baum-Connes and conjecture. We welcome young researchers in these, and neighbouring areas to participate.

**Lectures are given by:**

-Siegfried Echterhoff (Münster)

-Erik Guentner (Hawaii)

-Michael Puschnigg (Aix-Marseille)

-Mikael de la Salle (ENS Lyon)

-Guoliang Yu (Texas A&M)

Please register **here**

For information on funding we refer you to the website. The workshop has been organized together with the ANR SingStar project. Please feel free to forward the announcement to people who may be interested.

**Organizer:** Martijn Caspers, Maria-Paula Gomez, Pierre-Yves Le Gall, Walther Paravicini

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