# Dates

### Johannes Rau (Bogotá): Tropical geometry and some applications

In my talk, I would like to introduce the main ideas of tropical geometry (from a geometric point of view) and then focus on some of the main applicactions, in particular, in the context of real algebraic geometry. In this context, tropical geometry can be understodd as a generalization of Viro's patchworking technique to construct real algebraic varieties with specific topological properties. Tropical methods can be used here to extend the technique to singular varieties and higher codimensions.

### Marwan Benyoussef: On the Hitchin morphism in positive characteristic

Location: The talk will be held via WebEx.

### Victor Martinez-Luaces: Visualizing roots of complex functions using sibling curves

Location: The talk will be held via WebEx. If you are interested in joining the meeting, please contact: beate.pierchalla@fu-berlin.de

### Serkan Emek: Iterated Robin problem for the higher order Poisson equation

Location: Die Veranstaltung wird via WebEx durchgeführt. Die Zugangsdaten werden noch bekannt gegeben.

### Angel Luis Munoz Castaneda: Degenerations of semistable principal G-bundles on curves

Location: Arnimallee 3, SR 024, 14195 Berlin

### The harmonic Green and Neumann functions of domains bounded by two intersecting circular arcs

Location: Arnimallee 3, SR 024, 14195 Berlin

### Oliver Labs: Cubic Surface Models and their Historical and Mathematical Background

In the 19 th century, cubic surfaces - defined by an implicit equation of degree three in three variables - were among the first interesting examples in the development of modern algebraic geometry. A well-known result by Arthur Cayley and George Salmon is that any smooth cubic contains exactly 27 straight lines. Other prominent facts are the classification of all cubic surfaces w.r.t. their singularities by Ludwig Schläfli, and Alfred Clebsch's birational map between the plane and such surfaces where six points play an essential role. The talk will present both the historical and the mathematical background of classical hand-crafted and also recent 3d-printed cubic surface models. Some of their fascinating features such as the movement of the straight lines as the surfaces vary may very well be visualized using interactive software. In 2011 and 2014, the speaker created two versions of a complete series of more than 45 types of 3d-printed cubic surface models. Copies of these are now part of several university collections such as those at Lisbon, Strasbourg, Dresden, and Mainz, as well as at the IHP at Paris. He will bring some examples of these sculptures with him in order to illustrate facts which may better be appreciated when seeing and touching a real object.

Location: HS 001/Arnimallee 3 (Tea/coffee will be served from 16:45 in room 006/A3.)

### Frank Neumann: Hochschild cohomology of dg-categories and spectral sequences

Location: SR 007/008, Arnimallee 6 (Tee/coffee will be served from 15:45 in room 006/A3)

### Vincent Trageser: On actions of non-reductive groups with a graded unipotent radical on affine varieties

Location: SR 140, A3 (Hinterhaus)

### Yorck Sommerhäuser: Hopf Algebras - A short introduction

Location: HS 001/A3 (Tee/coffee will be served from 15:45 in room 006/A3).

### Bernd Kreussler: Means, Braids and Triangle Equations

Location: HS 001, A3 (Tea & coffee will be served from 4:45 pm in room 006, A3)

### Alejandra Rincón Hidalgo: Bridgeland stability conditions on the n-Kronecker quiver

Location: SR 140, A3 (HH)

### Hanxing Lin: Introduction to Cauchy-Pompeiu type formulas on Riemann surfaces

Location: SR 140, A3 (HH)

### Heinrich Begehr: A hierarchy of complex partial differential operators II

Location: SR 140, A3 (HH)

### Heinrich Begehr: A hierarchy of complex partial differential operators

Location: SR 140, A3 (HH)

### Alejandra Rincón: Algebraic cycles and Roitman's theorem

Location: SR 025/026, Arnimallee 6.

### Matthew Spong: Geometric Invariant Theory over the reals

Location: SR 005, Arnimallee 3

### Nikolai Beck and Arijit Dey: Homotopic classification of vector bundles on smooth k-schemes

Location: SR 005, Arnimallee 3

### Arijit Dey: Homotopic properties of the canonical torsor on the Grassmannians

Location: SR 005, Arnimallee 3

### Victoria Hoskins: Anodyne extensions II

Location: SR 005, Arnimallee 3

### Joana Cirici: Anodyne extensions

Location: SR 005, Arnimallee 3

### Ángel Muñoz Castañeda: Excision for Picard groups and Karoubi-Villamayor K-theory

Abstract: We continue from last week by defining K_0 and K_1-regularity of a ring and prove that a regular ring is K_0 and K_1-regular. We show that distinguished squares of schemes give rise to an exact sequence relating their Picard groups and prove that K_0-regularity implies Pic-regularity. Then we define the Karoubi-Villamayor K-theory groups of a ring and relate these to the K_0 and K_1 groups. Further details: http://userpage.fu-berlin.de/hoskins/seminar.html [userpage.fu-berlin.de]

Location: Arnimalle 3, SR005

### Ángel Muñoz Castañeda: K_0 and K_1 for rings

Location: SR 005, Arnimallee 3

### Nickolai Beck: The A^1-homotopy category of smooth k-schemes

Location: SR 005, Arnimallee 3

### Anna Wißdorf: The simplicial homotopy category of sheaves

Location: SR 005, Arnimallee 3

### Eva Martínez: Sheaves in the Nisnevich topology

Location: SR 005, Arnimallee 3

### Elena Martinengo: An introduction to homotopical algebra

Location: SR 005, Arnimallee 3

### Vincent Trageser: Classification of principal bundles in algebraic topology

Location: Arnimalle 3, SR005

### Victoria Hoskins: Introduction to A^1- homotopy theory of schemes

Location: SR 005, Arnimallee 3

### Anna Wißdorf: The theorem of Mehta-Ramanathan

Location: Arnimallee 6, SR 025/026

### Nikolai Beck: Wonderful compactifications

Location: Arnimallee 6, SR 025/026

### Anna Wißdorf: Introduction to Arakelov Geometry II: Arakelov principal bundles

Location: Arnimallee 6, SR 025/026

### Eva Martínez: Introduction to Arakelov Geometry I: Arakelov vector bundles over arithmetic curves

Location: Arnimallee 6, SR 025/026

### Victoria Hoskins: Towards symplectic and hyperkähler quotients for non-reductive groups

Location: Arnimallee 6, SR 025/026

### Anna Wißdorf: Betti numbers of the moduli space of Higgs bundles of rank 2 and degree 1

Location: Arnimallee 6, SR 025/026

### Nikolai Beck: The gauge theoretic moduli space

Location: Arnimallee 6, SR 025/026

### Joana Cirici: Hitchin's Existence Theorem

Location: Arnimallee 6, SR 025/026

### Ángel Muñoz: Stability of Hitchin pairs

Location: Arnimallee 6, SR 025/026

### Joana Cirici: Uhlenbeck’s Compactness Theorem

Location: Arnimallee 6, SR 025/026

### Eva Martinez: Sobolev spaces of sections in fiber bundles

Location: Arnimallee 6, SR 025/026

### Vincent Trageser: Review of classical Sobolev theory

Location: Arnimallee 6, SR 025/026

### Ángel Muñoz: Hitchin’s self-duality equations

Location: Arnimallee 6, SR 025/026

### Arijit Dey: Bundles on toric varieties

Location: Arnimallee 6, SR 025/026

### Eva Martinez: Moduli spaces of stable rank 2 vector bundles on flag manifolds

Location: SR 005, Arnimallee 3

### Juan Pons: Donaldson’s proof of Narasimhan-Seshadri

Location: SR 005, Arnimallee 3

### Emilio Franco: Refined Hitchin-Kobayashi correspondence on elliptic curves

Location: SR 005, Arnimallee 3

### Nikolai Beck: Gauge theory of ﬁber bundles

Location: SR 005, Arnimallee 3

### Anna Wißdorf: The Theorem of Narasimhan and Seshadri

Location: SR 005, Arnimallee 3

### Joana Cirici: Computing the E-polynomial of character varieties

Location: SR 005, Arnimallee 3

### Juan Pons: Counting points of character varieties over ﬁnite ﬁelds.

Location: SR 005, Arnimallee 3

### Daniela Prata (Campinas, Brazil)

Location: SR 005, Arnimallee 3

### Simone Marchesi (Campinas Brazil)

Location: SR 130, Arnimallee 3, Hinterhaus

### Ángel Muñoz: Abelianization of the Hitchin system

Location: SR 005, Arnimallee 3

### Anna Wißdorf: Construction of the Harder-Narasimhan reduction

Location: SR 005, Arnimallee 3

### Anna Wißdorf: The Harder–Narasimhan reduction of a Higgs bundle.

Location: SR 005, Arnimallee 3

### Nickolai Beck: The moduli space of Higgs bundles.

Location: SR 005, Arnimallee 3

### Anna Wißdorf: Symplectic and Orthogonal Instantons

Location: SR 025/026, Arnimallee 6

### Nikolai Beck: Explicit Examples of Instanton Moduli Spaces II

Location: SR 025/026, Arnimallee 6

### Nikolai Beck: Explicit Examples of Instanton Moduli Spaces

Location: Arnimallee 6, SR 025/026

### Joanna Cirici: The Penrose Transform III : Cohomology and massless fields

Location: SR 025/026, Arnimallee 6

### Patricia Borges dos Santos: Complex ADHM equations and sheaves on P^3

Location: Arnimallee 6, SR 025/026

### Elena Martinengo: The Penrose Transformation

Location: Arnimallee 6, SR 025/026

### Juan Pons Llopis: From Differential to Algebraic Geometry: Penrose Twistor Spaces

Location: Arnimallee 6, SR 025/026.

### E.F.Gomez: Yang-Mills Equations and the Instanton Classification Problem

Location: Arnimallee 6, SR 025/026