## "Descartes, Euler, Gauss: From surfaces to integers". Hirzebruch lecture by Werner Ballmann on Monday, November 13, University Club Bonn

Geometric quantities of a surface, like distance, angle, or area, change when the surface is deformed. Euler discovered a quantity, the Euler characteristic, which remains unchanged. The formula of Gauss-Bonnet, a landmark result of mathematics, relates Euler characteristic with geometry. In the talk, I will present ideas of Descartes, Euler, and Gauss related to this formula.

## "Coarse Geometry". Hirzebruch colloquium talk by Walter Neumann

Coarse geometry can lead to useful classifications. For example, the word metric on a finitely presented group recognises (up to finite groups) if that group is the fundamental group of a 3-manifold and it carries a lot of information about the manifold. I will mainly talk about coarse geometry for complex surfaces, showing that bilipschitz geometry, which is purely topological and ignores any analytic structure, can recover the local analytic structure up to Zariski equisingularity. (Joint work with Anne Pichon).

## Jazz & Math: Public jazz performance with Rob Schneiderman & Friends

"Mathematics is not only a solo gig. When two or three mathematicians get together to share their ideas on how to attack a problem, sessions can easily stretch out for hours and even days. The dynamic is not unlike jazz musicians improvising with each spurring the other to go farther than they would go alone." **Rob Schneiderman**, New York based mathematician, regular guest at the Max Planck Institute for Mathematics, and professional Jazz pianist together with **John Goldsby** (bass) and **Hans Dekker** (drums) will explore the relations between **Jazz & Math** in a public concert, which will be followed by a get-together for an open discussion. (Free admission)

**Rob Schneiderman** was born in Boston, Massachusetts, and raised in California. His Jazz career began in San Diego playing piano for visiting soloists such as Eddie Harris or Harold Land. A move to New York in 1982 led to performing and touring experience with famous jazz musicians like Chet Baker, James Moody and Clifford Jordan, including trips to Europe and Japan. Rob Schneiderman has released several recordings as leader for the *Reservoir Music* label. These CDs contain over twenty Schneiderman originals as well as arrangements of many standards.

As a jazz educator, Rob Schneiderman taught as an adjunct professor in the Jazz departments of both William Paterson University and Queens College New York in addition to giving numerous workshops and teaching many students privately. He has also been on the faculty of *The Jazz School* in Berkeley.

In May 2001 Rob Schneiderman received a Ph.D. in Mathematics. After stints at the Max Planck Institute for Mathematics in Bonn, the Courant Institute at New York University, and the University of Pennsylvania, he is currently on the faculty of the Department of Mathematics and Computer Science at Lehman College, City University of New York. His area of interest is Low-dimensional Topology.

**John Goldsby** has been a member of the Westdeutscher Rundfunk Big Band (also known as the WDR Big Band or the Cologne Radio Big Band) since 1994. He was born and raised in Louisville, Kentucky. He played piano, guitar and electric bass before taking up the double bass at the age of 18. From 1980 to 1994, John Goldsby lived in New York City and was a fixture on the jazz scene there. He continues to contribute to the art form as a bassist, bandleader, composer, teacher, clinician and author. During his years in New York, he recorded with many world-class musicians, including Scott Hamilton, Mel Lewis, John Lewis, and the American Jazz Orchestra.

John Goldsby is well-known as a jazz educator and currently teaches at the Folkwang-Hochschule in Essen. He has also taught at the Cologne Musikhochschule, William Paterson College, Long Island University, and Columbia University. He has given jazz workshops all over the world and has written several books on jazz bass techniques.

**Hans Dekker** was born in Boekelo in the Netherlands and began to play the drums at the age of nine. He was introduced to jazz music by his father, who took him to an Art Blakey concert. After high school, Hans Dekker studied at the Amsterdam Academy of Music and started working with well-known Dutch and German musicians and orchestras. He plays regularly with famous jazz musicians, such as Scott Hamilton, Bob Brookmeyer, Dee Dee Bridgewater and world class ensembles, such as the Metropole Orchestra, Brussels Jazz Orchestra, Dutch Jazz Orchestra, and Jazz Orchestra of the Concertgebouw.

Hans Dekker has been on the faculty at the Institute of Arts in Enschede since 1995. He was a regular visiting instructor at the German Federal Jazz Orchestra (Bundesjazzorchester). Since 2005 is a member of the WDR Big Band.

## Escher and the Droste effect. Public talk by Hendrik Lenstra, Wednesday, 14 December

In 1956, the Dutch graphic artist M.C. Escher made an unusual lithograph with the title `Print Gallery‘. It shows a young man viewing a print in an exhibition gallery. Amongst the buildings depicted on the print, he sees paradoxically the very same gallery that he is standing in. A lot is known about the way in which Escher made his lithograph. It is not nearly as well known that it contains a hidden `Droste effect‘, or infinite repetition; but this is brought to light by a mathematical analysis of the studies used by Escher. On the basis of this discovery, a team of mathematicians at Leiden produced a series of hallucinating computer animations. These show, among others, what happens inside the mysterious spot in the middle of the lithograph that Escher left blank.

**Hendrik Lenstra** received his doctorate from the University of Amsterdam in 1977 and became a professor there in 1978. In 1987 he was appointed to the faculty of the University of California, Berkeley; starting in 1998, he divided his time between Berkeley and the University of Leiden, until 2003, when he retired from Berkeley to take a full-time position at Leiden. He was awarded the Spinoza prize in 1998, and on 24 April 2009 he was made a Knight of the Order of the Netherlands Lion. Lenstra has worked principally in computational number theory and is well known as the discoverer of the elliptic curve factorization method and a co-discoverer of the Lenstra–Lenstra–Lovász lattice basis reduction algorithm.

Hendrik Lenstra is currently Hirzebruch Visiting Professor at the Max Planck Institute for Mathematics in Bonn.

## "Cannons at Sparrows". Hirzebruch lecture by Günter M. Ziegler on Wednesday, November 2

The story told in this lecture starts with an innocuous little geometry problem, posed in a September 2006 blog entry by R. Nandakumar, an engineer from Calcutta, India: "Can you cut every polygon into a prescribed number of convex pieces that have equal area and equal perimeter?" This little problem is a "sparrow", tantalizing, not as easy as one could perhaps expect, and *Recreational Mathematics*: of no practical use.

I will sketch, however, how this little problem connects to very serious mathematics, including Computational Geometry: For the modelling of this problem we employ insights from a key area of *Applied Mathematics*, the Theory of Optimal Transportation, which leads to weighted Voronoi diagrams with prescribed areas. This will set up the stage for application of a major tool from *Very Pure Mathematics*, known as Equivariant Obstruction Theory. This is a "cannon", and we'll have fun with shooting it at the sparrow.

On the way to a solution, I will try to illustrate the workings of Equivariant Obstruction Theory in a slide show. Combinatorial properties of the permutahedron turn out to be essential. These will, at the end of the story, lead us back to India, with some time travel 100 years into the past: For the last step in our (partial) solution of the sparrows problem we need a simple divisibility property for the numbers in Pascal’s triangle, which was first observed by Balak Ram, in Madras 1909.

But even if the existence problem is solved, the Computational Geometry problem is not: If the solution exists, how do you find one? This problem will be left to you. Instead, I will comment on the strained relationship between cannons and sparrows, and to this avail quote a poem by Hans Magnus Enzensberger.

**Günter M. Ziegler** is a professor of mathematics at Freie Universität Berlin. His current work connects combinatorics and discrete geometry (especially polytopes) with topology (in particular configuration spaces). His honours include a Leibniz Prize (2001), the MAA Chauvenet Prize (2004), and the 2008 Communicator Award, as well as an ERC Advanced Grant (2010–2015). He presented invited lectures at the ICMs in Beijing (2002), Hyderabad (2016) and Seoul (2014). From 2006 to 2008, he was President of the German Mathematical Society. He is a member of the Executive Board of the Berlin-Brandenburg Academy of Sciences and a member of the Senate of the German Science Foundation.

(Photo: Sven Paustian/Piper Verlag)

## Hausdorff Cinema at MPIM: The Discrete Charm of Geometry

A team of mathematicians is working together on a big project. Excitement of discovery, hope and disappointment, competition and recognition are shown from an infinitely close distance. Scientists united by the idea of discretization, which, in short, means: constructing continuous objects from basic building blocks. Akin to the scientists’ search for the right discretization of continuum, this film itself is composed of fragments – individual characters of different ages, temperaments and scientific approaches – which form a single continuous melody. The question of where the boundaries lie between mathematics and the lives of those who are involved in it and how much they are willing to sacrifice is as important as the search for precise scientific answers. A unique and unprecedented dive into the unknown world of mathematicians.

Entry is free; there will be time for discussion after the movie.

More information about the movie project can be found here .

Was tun Mathematikerinnen und Mathematiker? Ekaterina Eremenko, erfahrene Berliner Filmemacherin („Colors of Maths“), zeigt einen Blick durchs Schlüsselloch in die rätselhafte Welt der Mathematik in ihrem neuen Dokumentarfilm: Sie hat ein Team von Forscherinnen und Forschern über ein Jahr lang mit der Kamera begleitet. Das Ergebnis ist ein einzigartiger und künstlerischer Film über Begeisterung, Hoffnung und Bangen, Konkurrenz und Anerkennung in der Mathematik. Die in dem Film portraitierte Forschergruppe arbeitet weltweit an dem Problem der Diskretisierung kontinuierlicher Objekte und Prozesse, im Zentrum steht ein Team an der TU Berlin, angesiedelt am Sonderforschungsbereich „Diskretisierung in Geometrie und Dynamik". Ekaterina Eremenko zeigt Größen wie John Nash und Freeman Dyson und den Arbeitsalltag: Wie ringen die Berliner Wissenschaftler um Lösungen, wie bringen sie ihr Leben mit der Mathematik in Einklang?

Der Eintritt ist frei; nach dem Film gibt es die Möglichkeit, über das Gesehene zu diskutieren.

Weitere Informationen zum Filmprojekt finden Sie hier .

## MPIM at play: Informal concert on Thursday, January 21

This Thursday, January 21st at 19:00h, members of the larger MPIM community will give us the honor of an informal musical concert. First, Carmen Rovi (Piano), Matthias Kreck (Cello), and Yael Fregier (Baritone) will play and sing classical pieces by Mozart, Schubert, Schumann, and Wagner. This is followed by a short break and some traditional folk music performed by the MPIM folk group with Tim Ballance (fiddle), Kristian Hodén (button accordeon), Pavel Mnev (flutes), Davide Spriano (electric bass), and Alessandro Valentino (acoustic guitar). Everybody from the math community in Bonn and their families are welcome.

## A Voyage of the Intellects: A Global History of Mathematics in the 17th century

**Tomoko L. Kitagawa**is a historian based in Cambridge, England. She is an author of five books in Japanese, including a national bestseller (2012) and the most recent one on the history of mathematics (2015). Her bachelor degree is in mathematics, and she has worked as a state diplomat before receiving her Ph.D. in history from Princeton University (2009). She taught history at Harvard University (2009-2012), where she was awarded a teaching certificate for three successive years and cited as one of the Class 2012’s Favorite Professors.

## Geometry, Analysis, and Gravitation. Hirzebruch Lecture 2014 by Gerhard Huisken

Since ancient times geometric concepts have been used to model astronomical phenomena such as the motion of the planets. In modern times geometry has merged with analysis to provide accurate models of gravitational phenomena involving stars and their planets, black holes and gravitational waves in the context of General Relativity - with the new mathematical insights leading also to progress in the understanding of many other phenomena surrounding us. The lecture describes in a non-technical way how ancient geometric concepts such as the isoperimetric inequality as well as classical concepts from Newtonian physics reappear in the curved space-times of General Relativity.

**Gerhard Huisken** PhD in Mathematics, University of Heidelberg 1983. Postdoctoral Fellow, Australian National University, Canberra. Habilitation University of Heidelberg 1986. Visiting Professor, University of California San Diego, 1986. Faculty position, Australian National University, Canberra 1986-1992. Professor, University of Tübingen 1992-2002. Dean, Faculty of Mathematics, Tübingen, 1996-1998. Visiting Professor, Princeton University 1990-2000. Director, Max Planck Institut für Gravitational Physics, 2002-2013. Since 2013 Director of the Mathematische Forschungsinstitut Oberwolfach and Professor at the University of Tübingen. Medal of the Australian Mathematical Society 1991. Leibniz Prize 2003. Fellow of the Heidelberg Academy for Sciences and Humanities, the Berlin-Brandenburg Academy of Sciences and Humanities, the German Academy of Sciences Leopoldina, and the American Mathematical Society.

**The Hirzebruch Lecture** is an annual one hour lecture for a general academic audience featuring a prominent speaker, which aims at illustrating the relation between mathematics and other fields like society, art, etc. It has been established on the occasion of Prof. Friedrich Hirzebruch's 80th birthday in 2007 and is jointly organized by the Max Planck Institute for Mathematics, the University Club, and the Hausdorff Center for Mathematics in Bonn. It is followed by a reception.

## Do musical improvisation and mathematics research have anything in common? A public jazz performance and mathematics discussion with Rob Schneiderman

"Mathematics is not only a solo gig. When two or three mathematicians get together to share their ideas on how to attack a problem, sessions can easily stretch out for hours and even days. The dynamic is not unlike jazz musicians improvising with each spurring the other to go farther than they would go alone." **Rob Schneiderman**, New York based mathematician, regular guest at the Max Planck Institute for Mathematics, and professional Jazz pianist together with **John Goldsby** (bass) and **Hans Dekker** (drums) will explore the relations between **Jazz & Math** in a public concert and an open discussion. (Free admission)

**Rob Schneiderman** was born in Boston, Massachusetts, and raised in California. His Jazz career began in San Diego playing piano for visiting soloists such as Eddie Harris or Harold Land. A move to New York in 1982 led to performing and touring experience with famous jazz musicians like Chet Baker, James Moody and Clifford Jordan, including trips to Europe and Japan. Rob Schneiderman has released several recordings as leader for the *Reservoir Music* label. These CDs contain over twenty Schneiderman originals as well as arrangements of many standards.

As a jazz educator, Rob Schneiderman taught as an adjunct professor in the Jazz departments of both William Paterson University and Queens College New York in addition to giving numerous workshops and teaching many students privately. He has also been on the faculty of *The Jazz School* in Berkeley.

In May 2001 Rob Schneiderman received a Ph.D. in Mathematics. After stints at the Max Planck Institute for Mathematics in Bonn, the Courant Institute at New York University, and the University of Pennsylvania, he is currently on the faculty of the Department of Mathematics and Computer Science at Lehman College, City University of New York. His area of interest is Low-dimensional Topology.

**John Goldsby** has been a member of the Westdeutscher Rundfunk Big Band (also known as the WDR Big Band or the Cologne Radio Big Band) since 1994. He was born and raised in Louisville, Kentucky. He played piano, guitar and electric bass before taking up the double bass at the age of 18. From 1980 to 1994, John Goldsby lived in New York City and was a fixture on the jazz scene there. He continues to contribute to the art form as a bassist, bandleader, composer, teacher, clinician and author. During his years in New York, he recorded with many world-class musicians, including Scott Hamilton, Mel Lewis, John Lewis, and the American Jazz Orchestra.

John Goldsby is well-known as a jazz educator and currently teaches at the Folkwang-Hochschule in Essen. He has also taught at the Cologne Musikhochschule, William Paterson College, Long Island University, and Columbia University. He has given jazz workshops all over the world and has written several books on jazz bass techniques.

**Hans Dekker** was born in Boekelo in the Netherlands and began to play the drums at the age of nine. He was introduced to jazz music by his father, who took him to an Art Blakey concert. After high school, Hans Dekker studied at the Amsterdam Academy of Music and started working with well-known Dutch and German musicians and orchestras. He plays regularly with famous jazz musicians, such as Scott Hamilton, Bob Brookmeyer, Dee Dee Bridgewater and world class ensembles, such as the Metropole Orchestra, Brussels Jazz Orchestra, Dutch Jazz Orchestra, and Jazz Orchestra of the Concertgebouw.

Hans Dekker has been on the faculty at the Institute of Arts in Enschede since 1995. He was a regular visiting instructor at the German Federal Jazz Orchestra (Bundesjazzorchester). Since 2005 is a member of the WDR Big Band.

## „The extra-scientific in scientific creativity: Galileo's mechanics and Bohr's quantum atom“. Hirzebruch lecture by John Heilbron

**John L. Heilbron** is Professor of History and Vice-Chancellor Emeritus, University of California, Berkeley, and Honorary Fellow, Worcester College, Oxford. His talk is drawn from material in and reflections on his recent books, *Galileo* (2010) and (with Finn Aaserud) *Love, literature, and the quantum atom. Niels Bohr's 1913 trilogy revisited* (2013), both from Oxford University Press.

**The Hirzebruch Lecture** is an annual one hour lecture for a general academic audience featuring a prominent speaker, which aims at illustrating the relation between mathematics and other fields like society, art, etc. It has been established on the occasion of Prof. Friedrich Hirzebruch's 80th birthday in 2007 and is jointly organized by the Max Planck Institute for Mathematics, the University Club, and the Hausdorff Center for Mathematics in Bonn. It is followed by a reception.

## Public Lecture: Mathematical Perspectives on Music-theoretical Knowledge

The music theorist Thomas Noll, currently a guest at the Max Planck Institute for Mathematics, will give a public lecture about his research on the relation between music and mathematics.

Download commented slides of the talk (pdf)

**Abstract:** Music theorists emphasize the historical anchors of their field and trace the history of ideas as a substantial part of their collective knowledge. Mathematical investigations offer a complementary approach, where mathematical redefinitions of historically grown concepts are studied with respect to their logical interdependencies. Within the last three decades a fruitful dialogue between the two types of investigation emerged. In my talk, I will share some instances where central elements of traditional knowledge appear in a promising new light after mathematical investigation. For instance, the decomposition of the dorian mode d-e-f-g-a-b-c-(d) into a species of the fifth (tone semitone tone tone) and a species of the fourth (tone semitone tone) suggests the consideration of an automorphism f(a) = abaa, f(b) = aba of the free group F2 over the generators a and b. Starting from such a definition, various music-theoretically relevant issues around diatonicity can then be re-interpreted on the basis of known facts from algebraic combinatorics on words. But also fundament progressions, a main subject in harmonic tonality, can be revisited in this context. In addition to the illustrative role of these examples I will attempt to position them within ongoing projects in mathematical music theory. The applied mathematical concepts include group actions, monoid actions, algebraic combinatorics on words, formal concept analysis, and discrete Fourier transforms.

**Thomas Noll** (Germany/Spain) works in mathematical music theory as his main research area. He studied mathematics (diploma) in Jena and semiotics (PhD) at the TU Berlin. From 1998 - 2003 he was the leader of an interdisciplinary research group on mathematical and computational music theory at that same university. After two years of teaching in theoretical informatics at the TU Berlin he works since 2005 as a lecturer in music theory at the Escola Superior de Musica de Catalunya in Barcelona. He was co-editor of the "Journal of Mathematics and Music" (2006 - 2012) and serves as reviewer for several journals and conferences in the field. He also is active in popularizing mathematical music theory for a wider audience. He is currently a guest at the MPIM collaborating with guest Thomas Fiore (Topology).

## German Movie Premiere: The Genius of Srinivasa Ramanujan

This documentary is a celebration of the story of Ramanujan while walking in his footsteps trying to fathom his genius. I will begin with a very short (less than 5 minutes) introduction to the making of the documentary. Then we will watch the documentary; it is about one hour long. Finally, I can (try to) answer any questions the audience might have.

"The Genius of Srinivasa Ramanujan" was directed by Nandan Kudhyadi, and co-produced by Vigyan Prasar in New Delhi, and IISER Pune. The documentary features Ken Ono, Raghuram, K.Srinivasa Rao and T.V.Venkateswaran. The filming was done mostly in Kumbakonam, Nammakal, Erode, Chennai (all in India), and Cambridge, UK. The documentary also involves conversations with: Bruce Berndt, George Andrews, John Coates, Ram Murty and Kumar Murty. It was released in IISER Pune in March 2013.

## The Secret Mathematicians. Hirzebruch lecture by Marcus du Sautoy

From composers to painters, writers to choreographers, the mathematician’s palette of shapes, patterns and numbers has proved a powerful inspiration. Often subconsciously artists are drawn to the same structures that fascinate mathematicians as they constantly hunt for interesting new structures to frame their creative process. Through the work of artists like Borges and Dali, Messiaen and Laban, Professor du Sautoy will explore the hidden mathematical ideas that underpin their creative output and reveal that the work of the mathematician is also driven by strong aesthetic values.

**Marcus du Sautoy** is the Charles Simonyi Professor for the Public Understanding of Science and Professor of Mathematics at the University of Oxford and a Fellow of New College. In 2001 he won the prestigious Berwick Prize of the London Mathematical Society awarded every two years to reward the best mathematical research made by a mathematician under 40. In 2004 Esquire Magazine chose him as one of the 100 most influential people under 40 in Britain and in 2008 he was included in the prestigious directory Who’s Who. In 2009 he was awarded the Royal Society’s Faraday Prize, the UK’s premier award for excellence in communicating science.

He is author of numerous academic articles and books on mathematics. He has been a visiting Professor at the École Normale Supérieure in Paris, the Max Planck Institute for Mathematics in Bonn, the Hebrew University in Jerusalem and the Australian National University in Canberra.

Marcus du Sautoy is author of the best-selling popular mathematics book "The Music of the Primes" published by Fourth Estate in 2003 and translated into 10 languages. It has won two major prizes in Italy and Germany for the best popular science book of the year. Marcus du Sautoy writes for the Times, Daily Telegraph, Independent and the Guardian and is frequently asked for comment on BBC radio and television. For several years he had a regular column in the Times called Sexy Science. He was presenter of BBC4’s TV game show Mind Games, for which he was nominated for the Royal Society of Television’s Best Newcomer to a Network award. He has written and presented several series for radio including: 5 Shapes for BBC radio 4 in 2004 and Maths and Music for the Essay on BBC radio 3 in 2007 and The Baroque: from ecstasy to infinity for BBC radio 3 in 2009. In 2010 he wrote and presented a ten part series for BBC Radio 4 called A Short History of Mathematics.

**The Hirzebruch Lecture** is an annual one hour lecture for a general academic audience featuring a prominent speaker, which aims at illustrating the relation between mathematics and other fields like society, art, etc. It has been established on the occasion of Prof. Friedrich Hirzebruch's 80th birthday in 2007 and is organized by MPIM in collaboration with the University Club and the Hausdorff Center for Mathematics in Bonn. It is followed by a reception.

## "Late Style". Bonn premiere of film documentary about Yuri Manin

Anges Handwerk and Harrie Willems have made a remarkable documentary about the life and work of Yuri Manin, Emeritus Director at the Max Institute for Mathematics in Bonn, who began his career as a student at Moscow State University in the year of Stalin's death 1953 and whose subsequent professional life reflects the history of mathematics and mathematicians trying to overcome the political constraints of that time. The film will be shown for the first time in Bonn, prior to its publication by Springer in 2012. The directors will be present and available for questions and discussion after the screening.

**Yuri Ivanovich Manin** started his distinguished career as scientist at Moscow State University. There he received his bachelor's degree in 1958 but, even before this, his first mathematics paper On cubic congruences to a prime modulus (Russian) appeared in print. He continued to undertake research at the Steklov Mathematical Institute in Moscow advised by Igor Shafarevitsch and after the award of his doctorate in 1960 he was appointed as Principal Researcher at the Steklov Mathematical Institute and professor for algebra at the Moscow State University. In 1991/92 he was at the Columbia University and till 1993 at the MIT, remaining , in absentia, a member of the Steklov Institut in Moscow. Since 1992 he is member of the scientific board of the Max Planck Institut for Mathematics in Bonn and was its director from 1993 to 2005. For him and his wife Xenia Semenova, Bonn became their main residence.

“The breadth of Manin's contributions have been remarkable. He has written papers on: algebraic geometry including ones on the Mordell conjecture for function fields and a joint paper with V Iskovskikh on the counter-example to the Lüroth problem; number theory including ones about torsion points on elliptic curves, p-adic modular forms, and on rational points on Fano varieties; and differential equations and mathematical physics including ones on string theory and quantum groups. He has also written famous papers on formal groups, the arithmetic of rational surfaces, cubic hypersurfaces, noncommutative algebraic geometry, instanton vector bundles and mathematical logic.”

**About the directors of the film:** Agnes Handwerk, Hamburg, and Harrie Willems, Amsterdam, both work as free journalists. They are the authors of the acclaimed documentary "Wolfgan Doeblin - A Mathematician Rediscovered". Agnes Handwerk recieved the Prize for Journalism of the German Mathematical Society DMV for a radio feature about Alexander Grothendieck.

## What is a random geometry? Hirzebruch-Vorlesung von Fieldsmedaillist Wendelin Werner

**Die Friedrich-Hirzebruch-Vorlesung** ist eine jährlich stattfindende Reihe von öffentlichen Vorträgen, die 2007 anlässlich des 80. Geburtstags von Prof. Friedrich Hirzebruch ins Leben gerufen wurde. Die Vorlesungen richten sich an ein breites Publikum und sollen die vielfältigen Verbindungen zwischen Mathematik, Kunst, Gesellschaft, und anderen Gebieten beleuchten. Die bisherigen Sprecher waren Sir Michael Atiyah, Hans Magnus Enzensberger, Don Zagier, Yuri Manin und Hendrik Lenstra.

**Wendelin Werner:** Geboren in 1968 in Köln. Französischer Staatsbürger seit 1977. Studium an der École Normale Superieure 1987-1991. Promotion an der Université Paris VI bei Jean-François Le Gall 1993. Forscher im CNRS 1991-1997. Professor an der Université Paris-Sud seit 1997 und École Normale Superieure seit 2005. Zahlreiche Preise, darunter Preis der Europäischen Mathematischen Gesellschaft 2000, Fermat-Preis 2001, Jacques-Herbrand-Preis 2003, Loève-Preis 2005, Pólya-Preis 2006, Fields-Medaille 2006. Mitglied der Académie des Sciences, Ehrenmitglied des Gonville and Caius College in Cambridge.

## Ein Abend im Grenzbereich zwischen Poesie und Mathematik

»Ein Mathematiker, der nicht etwas Poet ist, wird nimmer ein vollkommener Mathematiker sein«, schreibt der Mathematiker Weierstraß im August 1883 an Sofja Kowalewskaja. Aber ist die Mathematik als exakteste der Wissenschaften nicht eigentlich die Gegenspielerin der Poesie? Ist es nicht wie für Lessing »gewiß, daß dasjenige, was die Poesie von der Mathematik borgt, den Witz vertrocknet und ihn zu einer körperlichen Genauigkeit gewöhnet, welche mit der metaphysischen Genauigkeit der Dichter gar keine Verwandtschaft hat«? Der österreichische Lyriker Oswald Egger widerlegt mit seinem Werk das Klischee der Unvereinbarkeit von Dichtung und exakter Wissenschaft. Immer wieder hat er sich engagiert und produktiv mit geometrischen und algebraischen Strukturen der modernen Mathematik auseinandergesetzt, vom »Lehrbuch der literarischen Mathematik« von 1998 bis zu seinem 2008 in der Edition Unseld erschienen Band »Diskrete Stetigkeit«.

Oswald Egger stellt Auszüge aus seinem Werk vor und diskutiert mit dem Mathematiker Ralph Kaufmann über das Verhältnis von Poesie und Mathematik. Die Germanistin Andrea Albrecht kommentiert das Werk Oswald Eggers aus literaturwissenschaftlicher Sicht.

Weitere Informationen: http://www.mpim-bonn.mpg.de/node/3498

## Politische Raumkurven. Zur hundertjährigen Geschichte einer mathematischen "Tatsache"

Ein kurzes Gegenbeispiel, das der junge Theodor Vahlen 1891 veröffentlichte und das ein halbes Jahrundert lang als Teil des mathematisches Menscheitswissens galt, wurde plötzlich im Zweiten Weltkrieg druch Oskar Perron zum Mittelpunkt einer politisch-mathematischen Debatte. Im ersten Teil des Vortrags erinnern wir zunächst an diese Geschichte. Das Beispiel ist schon deshalb interessant, weil mathematisch-politische Debatten nicht sehr häufig sind. Ausserdem aber werfen wir im zweiten Teil einen frischen Blick auf das Problem.

## Escher and the Droste effect

In 1956, the Dutch graphic artist M.C. Escher made an unusual lithograph with the title `Print Gallery‘. It shows a young man viewing a print in an exhibition gallery. Amongst the buildings depicted on the print, he sees paradoxically the very same gallery that he is standing in. A lot is known about the way in which Escher made his lithograph. It is not nearly as well known that it contains a hidden `Droste effect‘, or infinite repetition; but this is brought to light by a mathematical analysis of the studies used by Escher. On the basis of this discovery, a team of mathematicians at Leiden produced a series of hallucinating computer animations. These show, among others, what happens inside the mysterious spot in the middle of the lithograph that Escher left blank.