INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN

Activity report

Institut Mittag-Leffler is a Nordic research institute for mathematics. It was founded in 1916 by Gösta Mittag-Leffler and his wife Signe, who donated their magnificent villa with its first-class library for the purpose of creating the Institute that bears their name.

The Institute is today an active international center for front-line research in the mathematical sciences, operating under the auspices of the Royal Swedish Academy of Sciences. It enjoys the economic support of national funding agencies from all the Nordic countries, as well as of some private foundations. The main activities at the Institute are the research programs and the publication of two research journals.

The Institute conducts semester-long programs aimed at research in some area in pure or applied mathematics of current interest. The ambition is that over time all areas of current interest to mathematicians in the Nordic countries are served. The programs during the current 10-year period – past, present and future – are:

• Probability and conformal mappings, fall 2001 and spring 2002. • Partial differential equations and spectral theory, fall 2002. • Mathematical control and systems theory, spring 2003. • Noncommutative geometry, fall 2003 and spring 2004. • Queuing theory and teletraffic theory, fall 2004. • Algebraic , spring 2005. • Wave motion, fall 2005. • Algebraic topology, spring 2006. • Moduli spaces, fall 2006 and spring of 2007. • Stochastic partial differential equations, fall 2007. • Several complex variables, spring 2008. • Geometry, analysis, and general relativity, fall 2008. • Discrete probability, spring 2009. • Mathematical logic: Set theory and model theory, fall 2009. • Dynamical systems and PDEs, spring 2010. • Quantum information theory, fall 2010. • Algebraic geometry with a view to applications, spring 2011 • Complex analysis and integrable systems, fall 2011. • Geometric and analytic aspects of group theory, spring 2012.

The subject area for each research program is decided circa 2 1/2 years in advance by the board of the Institute, based on submitted proposals. An international evaluation committee is appointed, which meets at the Institute and conducts interviews with the prospective organizers as a basis for the recommendations submitted to the board.

Each research program is led by an organizing committee. Based on the recommendations of this committee the Institute invites senior and junior mathematicians to come and work together at the Institute. The senior participants are chosen among the internationally leading mathematicians in the given area. To the junior

1 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS participants, typically recent Ph.D.s, we offer fellowships, open to everyone to apply for. Mathematicians from the Nordic countries are given a slight priority, however we make sure that scientific caliber and a good mixture of talents and backgrounds have top priority, to optimize the creative environment at the Institute.

During 2009 there were a total of 151 visiting researchers, working a total of 272.5 man- months at the Institute as part of the following programs:

Discrete Probability, spring of 2009 Organizing committee: Sven Erick Alm, Uppslala Olle Häggström, CTH, Göteborg Svante Janson, Uppsala Kurt Johansson, KTH, Stockholm Jeff Steif, CTH, Göteborg

Mathematical Logic: Set Theory, fall of 2009 Organizing committee: Dag Normann, Oslo Erik Palmgren, Uppsala Jouko Väänänen, Amsterdam and Helsinki Hugh Woodin, Berkeley

Detailed reports and documentation on these programs can be found later in this annual report.

The research programs are conducted in a way that recognizes the immense value of having the time and the freedom to follow one's research interests wherever developments lead rather than having to deliver on predetermined goals. For this reason we require of all participants that they stay at least one month, to ensure time for substantial work.

An aspect of the programs that is emphasized is to provide good postdoctoral training to the junior participants. Special seminars and minicourses are given specifically for them. In addition to these area-specific research programs we have the RIP program (Research in Peace), which allows Nordic mathematicians to spend time at the Institute for independent research.

The Institute publishes two journals, Acta Mathematica (founded in 1882) and Arkiv för matematik (founded in 1903). Information about the journals is given on page www.mittag- leffler.se/publications/. Acta Mathematica has won a standing as one of a handful of journals generally considered to be the most important ones among all mathematics research journals.

Institut Mittag-Leffler is an active participant in international scientific life. In particular, it participates in international networks of research institutes in mathematics. For instance, we belong to ERCOM (European Research Centers on Mathematics), a network of European sister institutes. We also belong to EPDI (European Post-Doctoral Institute), a collaboration between 9 institutes for jointly awarding postdoctoral fellowships to Europe's most promising young mathematicians.

During 13-14 March Institut Mittag-Leffler hosted the annual ERCOM meeting. 30 directors and administrators representing 21 of the 26 ERCOM member institutes met in Djursholm to discuss matters of common concern and to share information.

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Participants at the ERCOM meeting

The efforts to improve the Institute's financial situation have led to some small progress during 2009. Being a Nordic institute, we benefit from contributions from all Nordic countries (including Iceland). On 22 September a Nordic meeting was held at the Institute to discuss its financial basis. Representatives from the national research councils of Denmark, Finland, Norway and were present, as well as mathematicians from these countries. The meeting indicated a general willingness from our neighboring countries to increase their contributions.

Institut Mittag-Leffler extends its warm gratitude to all organizations and individuals who via grants and contributions of various kinds have made the work of the Institute possible during the year 2009.

Anders Björner Director

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Contributors

The Institute is very grateful to the following organizations and individuals for contributions and support during 2009:

The Swedish Research Council (Vetenskapsrådet) Academy of Finland The Danish Research Councils The Icelandic Mathematical Society The Research Council of Norway Acta Mathematicas fond Barbro Osher Pro Suecia Foundation Department of Mathematics, University of Oslo European Science Foundation's Set theory Research Network INFTY program Fonden ”Till bröderna Jacob och Marcus Wallenbergs minne” Stiftelsen G.S. Magnusons fond The Anna-Greta and Holger Crafoord Fund

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Discrete Probability

Scientific report 2009 spring

The spring 2009 Mittag-Leffler programme on discrete probability saw intense work in the intended broad spectrum ranging from, on one hand, basic probabilistic objects such as Markov chains, random walks, random graphs and random matrices, to, on the other hand, applications in computer science, statistical mechanics and the modeling of epidemics and social networks.

A central meeting point for the participants was the seminar taking place Tuesdays and Thursdays; a total of 74 seminars were delivered. The seminar was very lively and led (together with the frequent more informal discussions during coffee breaks, in corridors and in hallways) to several unexpected collaborations. Recurrent themes covered in the seminar from a variety of angles include, for instance, the Ising model, Poisson processes, sorting and selection algorithms, Gaussian unitary ensembles, percolation models including dynamical percolation, different aspects of random graphs, and random walks with various (self-)interactions or in random environments.

There were a number of research projects completed in the area of percolation, particle systems and related topics. John Wierman, who participated the entire semester, showed in collaborative work that certain pairs of 2-dimensional lattices have the same critical exponents. Remco van der Hofstad succeeded in uncovering the structure of the size of the largest component for nonhomogeneous graphs; the critical quantity turns out to be the tail behavior of the degree. Jonathon Peterson and Timo Seppäläinen obtained very precise results concerning current fluctuations for a system of random walks moving in a common fixed random environment; it turns out that the fluctuations are occurring at two different scales. Maria Deijfen and Olle Häggström constructed an example of a percolation model where the speed of a biased random walk on the cluster is not monotone in the bias; this monotonicity is believed to hold for i.i.d. percolation. This example therefore shows that the i.i.d. assumption is critical.

One important area studied during the program was random graphs. In particular, progress was made on several fronts in the study of inhomogeneous random graphs, with contributions in the form of completed preprints by Tom Britton, Maria Deijfen, Remco van der Hofstad, Svante Janson, Mathias Lindholm, Tomasz \Luczak, Ilkka Norros, Oliver Riordan and Tatyana Turova. As an important example we would like to mention the result by Tatyana Turova describing the distribution of the sizes of the largest components of an inhomogeneous in the critical window; this is a major generalization of a well-known result by Aldous (1997) for the standard Erdös-Rényi random graphs. The result turns out to be essentially the same as in the standard case, provided a third moment is finite.

Other random graph problems studied include the diameter in the standard random graph process (\Luczak and Taral Guldahl Seierstad); high-dimensional models (Markus Heydenreich and van der Hofstad); connections to graph limits (Janson); recursive directed graphs (Luc Devroye and Janson); correlations in randomly oriented graphs (Sven Erick Alm and Svante Linusson); random lifts and large deviation estimates (Janson and Andrzej Rucinski). The demographics of the programme was very broad agewise, and somewhat tilted genderwise. A core group of young postdocs staying throughout the programme was of particular importance for holding it together, while more senior participants (with a few

5 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS exceptions) tended to stay for only parts of it but made important contributions nevertheless.

At present 37 preprints are listed as resulting from the programme, but this is not entirely representative as many advances made during the programme are yet to be written down in preprint form. A key participant from a scientific point of view was Svante Janson, as evidenced by the fact that he (co-)authored no less than 14 of the 37 preprints.

As a kind of satellite meeting for the Mittag-Leffler programme, a special session on discrete probability was organized at the 25th Nordic and 1st British-Nordic Congress of Mathematicians in Oslo in June 2009.

Organizing committee: Sven Erick Alm, Uppsala, Olle Häggström, Chalmers, Svante Janson, Uppsala, Kurt Johansson, KTH, Jeff Steif, Chalmers.

On behalf of the organizing committee,

Sven Erick Alm

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Discrete Probability

Participants 2009 spring

Name University City Arrival Departure Alm, Sven Erick Uppsala 15 Jan 15 Jun Austrin, Per KTH Stockholm 15 Jan 15 Jun Barbour, Andrew Universität Zürich Zürich 16 May 13 Jun Beffara, Vincent UMPA-ENS Lyon Lyon 15 Jan 8 Feb Bender, Martin University of Leuven Leuven 11 May 31 May Berg, van den, Jacob CWI Amsterdam 31 Mar 29 Apr 2 Jun 12 Jun Einstein Institute of Berger, Noam Jerusalem 1 Feb 27 Feb Mathematics Björnberg, Jakob Statistical Laboratory Cambridge 15 Jan 15 Jun Bollobas, Bela University of Cambridge Cambridge 6 Apr 8 Apr Britton, Tom Stockholm 14 Apr 20 May Broman, Erik Chalmers Göteborg 15 Jan 15 Jun Camia, Federico Vrije Universiteit Amsterdam 16 Feb 14 Mar Deijfen, Maria Stockholm University Stockholm 15 Jan 15 Jun Devroye, Luc McGill University Montreal 10 May 29 May Eriksson, Kimmo Mälardalens högskola Västerås 14 Apr 8 May Ferrari, Patrik University of Bonn Bonn 1 Mar 27 Mar Fill, Jim Johns Hopkins University Baltimore 17 May 9 Jun Fribergh, Alexander Université Lyon 1 Lyon 15 Jan 8 Apr Gantert, Nina University of Münster Münster 2 Mar 26 Mar Garban, Christophe Universite' Paris Sud Paris 15 Jan 15 Mar 10 May 23 May Guttmann, Tony University of Melbourne Victoria 15 May 15 Jun Hammond, Alan ENS Paris 6 Feb 15 Mar 18 May 16 Jun Hegarty, Peter Chalmers Göteborg 16 Mar 14 Apr Heydenreich, Markus Vrije Universiteit Amsterdan 25 Jan 22 Feb Hoffman, Chris University of Washington Seattle 16 May 15 Jun Hofstad, van der, Eindhoven University of Eindhoven 15 Jan 29 Jan Remco Technology Hollander, den, Frank Leiden University Leiden 1 Feb 27 Feb Holmgren, Cecilia Uppsala UniversityU Uppsala 15 Jan 15 Jun Holroyd, Alexander University of British Columbia Vancouver 9 Feb 16 Apr Holst, Lars KTH Stockholm 15 Jan 15 Jun Hwang, Hsien-Kuei Academia Sinica Taipei 27 Jan 14 Feb Häggström, Olle Chalmers Göteborg 2 Mar 5 Jun Janson, Svante Uppsala University Uppsala 15 Jan 11 Jun Johansson A., Anders Högskolan i Gävle Gävle 3 Mar 30 Apr Johansson, Fredrik KTH Stockholm 30 Jan 15 Jun Johansson K., Kurt KTH Stockholm 15 Jan 15 Jun

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Jonasson, Johan Chalmers Göteborg 6 Apr 30 Apr Jones, Liza University of Oxford Oxford 15 Jan 15 Jun Kahn, Jeff Rutgers University Piscataway 15 May 15 Jun Kalai, Gil Hebrew University Jerusalem 1 Jun 15 Jun Kang, Mihyun Technische Universität Berlin Berlin 1 Feb 28 Feb Karonski, Michal Adam Mickiewicz University Poznan 19 Jan 11 Feb 26 May 15 Jun Kesten, Harry Cornell University Ithaca 20 Apr 14 May Lagerås, Andreas Stockholm University Stockholm 15 Jan 15 Jun Limic, Vlada Université de Provence Marseille 1 Apr 30 Apr 3 Jun 14 Jun Lindholm, Mathias Stockholm University Stockholm 15 Jan 15 Jun Linusson, Svante KTH Stockholm 15 Jan 15 Jun Louchard, Guy Université Libre de Bruxelles Bruxelles 23 Feb 27 Feb Luczak M, Malwina London School of Economics London 23 Mar 17 Apr Luczak T, Tomasz Adam Mickiewicz University Poznan 15 Jan 31 Mar Markström, Klas Umeå University Umeå 2 Feb 07 May Martin, James St Hugh's College Oxford 22 Feb 25 Mar Martin-Löf, Anders Stockholm University Stockholm 15 Jan 15 Jun McDiarmid, Colin University of Oxford Oxford 29 Mar 26 Apr Metcalfe, Anthony University College Cork Cork 15 Jan 15 Jun Mossel, Elchanan University of California Berkeley 24 May 6 Jun Neininger, Ralph J.W.Goethe-Universität Frankfurt 16 Feb 28 Feb 25 May 4 Jun Nordenstam, Eric KTH Stockholm 15 Jan 15 Jun Norros, Ilkka VTT, Helsinki Helsinki 15 Jan 12 Mar Pete, Gabor Mcrosoft Research Redmond 6 May 5 Jun Peterson, Jonathon University of Wisconsin Madison 14 Jan 22 Mar Renlund, Henrik Uppsala University Uppsala 15 Jan 15 Jun Riordan, Oliver University of Oxford Oxford 26 Mar 22 Apr Rodl, Vojtech Emory University Atlanta 1 Jun 15 Jun Rucinski, Andrzej Adam Mickiewicz University Poznan 26 Jan 20 Feb 4 May 15 Jun Sanders, Tom Christ's College Cambridge 12 Jan 15 Jun Seierstad, Taral University of Oslo Oslo 15 Jan 15 Apr Seppäläinen, Timo University of Wisconsin-Madison Madison 16 Feb 12 Mar Sidoravicius, Vladas IMPA Rio de Janeiro 20 Apr 13 May Yorktown Sorkin, Gregory IBM Research 2 May 13 May Heights Spencer, Joel New York University New York 16 Mar 20 Apr Steif, Jeffrey Chalmers Göteborg 20 Jan 28 Feb 6 Apr 5 Jun Söderberg, Bo Lund University Lund 15 Apr 15 May Thorisson, Hermann University of Iceland Reykjavik 26 May 4 Jun Budapest University of Toth, Balint Budapest 26 Apr 9 May Technology 24 May 12 Jun Turova, Tatyana University of Lund Lund 15 Jan 15 Jun Tykesson, Johan Chalmers Göteborg 15 Jan 15 Jun

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Vallier, Thomas Institut Mittag-Leffler Djursholm 16 Mar 15 Jun Volkov, Stanislav University of Bristol Bristol 27 Apr 22 May Warfheimer, Marcus Chalmers Gothenburg 3 Feb 10 Feb Wierman, John Johns Hopkins University Baltimore 15 Jan 15 Jun Wilson, David Microsoft Corporation Redmond 1 Apr 5 May Wästlund, Johan Chalmers Göteborg 15 Jan 15 Feb 9 Apr 31 May Zeitouni, Ofer University of Minnesota Minneapolis 4 May 12 May

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Discrete Probability

Seminars 2009 spring

Andrew Barbour, Universität Zürich Quasi-stationary distributions

Gil Kalai, Hebrew University, Jerusalem Noise sensitivity

Svante Janson, Uppsala University Audience's choice Listeners are Kurt Johansson, Andrzej Rucinski, Vlada Limic and Jacob van den Berg. Photo: M. Wiberg

Balint Toth, Budapest University of Technology Long time asymptotics of self-repelling random walks

Gabor Pete, University of Toronto The scaling limits of dynamical and near-critical percolation, and the minimal spanning tree

Elchanan Mossel, University of California, Berkeley Quantitative social choice theory

Christopher Hoffman, University of Washington,Seattle Topology of random simplicial complexes

Alan Sokal, University of New York The multivariate Tutte polynomial for graphs and matroids

Jim Fill, Johns Hopkins University, Baltimore The numbers of symbol comparisons used by Quickselect and by Quicksort

Tony Guttmann, University of Melbourne, Victoria Lattice green functions and Calabi-Yau equations

Mathias Lindholm, Stockholm University Dynamic random networks

Martin Bender, University of Leuven Edge scaling limits for non-Hermitian random matrices

Thomas Vallier, Institut Mittag-Leffler, Djursholm Spread of activation on G(n,p)

Gregory Sorkin, IBM Research, Yorktown Heights Average-case analyses of Vickrey costs

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Stanislav Volkov, University of Bristol Going through a passport control with wife, or sequential adsorption at extremes

Maria Deijfen, Stockholm University Invariant random graphs with prescribed iid degrees

Kimmo Eriksson, Mälardalens Högskola, Västerås Cultural evolution as a random walk on integer partitions

Harry Kesten, Cornell University, Ithaca Random walk with occasionally modified transition probabilities

Ofer Zeitouni, University of Minnesota, Minneapolis Some aspects of large deviations for RWRE

Per Austrin, KTH, Stockholm Randomly supported independence

Svante Linusson and Sven Erick Alm, KTH, Stockholm and Uppsala University Surprising (?) correlations in randomly oriented graphs

Vladas Sidoravicius, IMPA, Rio de Janeiro Fixation in the activated random walk model

Tom Britton, Stockholm University Random networks and epidemics

Cecilia Holmgren, Uppsala University A weakly 1-stable limiting distribution for the number of random records and cuttings in split trees

Bo Söderberg, Lund University Random Feynman graphs

Vlada Limic, Université de Provence, Marseille The Lambda-coalescent speed of coming down from infinity

Anders Martin-Löf, Stockholm University Pfaff, Ising and statistical mechanics

Johan Jonasson, Chalmers, Gothenburg The bottom-to-top shuffle and the overlapping cycles shuffle

Colin McDiarmid, University of Oxford Random graphs with few disjoint cycles

Rob van den Berg, CWI, Amsterdam Sharpness of percolation transitions in some dependent 2D models

David Wilson, Microsoft Corporation, Redmond A sharp threshold for minimum bounded-depth and bounded-diameter spanning trees and Steiner trees in random networks

Oliver Riordan, Oxford University Random graphs, the cut metric and branching processes

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Johan Wästlund, Chalmers, Gothenburg Cancelling $\infty - \infty$ with games on graphs

Kurt Johansson, KTH, Stockholm Universality in random matrix theory

Anders Johansson, University of Gävle Factors in random graphs and hypergraphs

Malwina Luczak, London School of Economics Averaging over fast variables in the fluid limit for Markov chains

Lars Holst, KTH,Stockholm On records

Joel Spencer, New York University Finding Lovász's needle in an exponential haystack

Peter Hegarty, Chalmers, Gothenburg Concentration of measure in additive number theory

Erik Broman, Chalmers, Gothenburg (Some new and some old results in) fractal percolation

Olle Häggström, Chalmers, Gothenburg Dependent percolation on the square lattice

Svante Janson, Uppsala University Susceptibility of random graphs

John Wierman, Johns Hopkins University, Baltimore Triangle-duality and exact bond percolation thresholds

Anthony Metcalfe, University College Cork Structural and universality properties of Gelfand-Tsetlin patterns and their generalizations

Jakob Björnberg, Statistical Laboratory, Cambridge Stochastic geometry of the space-time Ising model

Eric Nordenstam, KTH, Stockholm The shuffling algorithm and the Aztec diamond

Patrik Ferrari, Weierstrass Institute, Berlin Limit processes in KPZ growth

Nina Gantert, University of Münster Nearly optimal paths and survival in a killed branching random walk

Liza Jones, Oxford University Infinite systems of non-colliding processes

James Martin, St Hugh's College, Oxford Multiclass queues and interchangeability

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Timo Seppäläinen, University of Wisconsin-Madison Fluctuation bounds for a class of zero range processes

Alan Hammond, ENS, Paris Trapping of a biased random walk on a supercritical tree

Christophe Garban, Université Paris Sud The Fourier spectrum of critical percolation

Federico Camia, Vrije Universiteit, Amsterdam Ising Euclidean fields and cluster area measures

Ralph Neininger, J.W. Goethe-Universität, Frankfurt Probabilistic analysis of "Quickselect" and the contraction method

Johan Tykesson, Chalmers, Gothenburg Aspects of continuum percolation in hyperbolic space

Klas Markström, Umeå University Random Cayley-like graphs

Alexander Holroyd, University of British Columbia, Vancouver Poisson matching

Frank den Hollander, Leiden University Intermittency on catalysts

Noam Berger, Einstein Institute of Mathematics, Jerusalem Slowdown estimates for ballistic random walk in random environment

Mihyun Kang, Technische Universität, Berlin An ice-type model for random graphs embeddable on a surface

Michal Karonski, Adam Mickiewicz University, Poznan Vertex-coloring edge-weightings

Markus Heydenreich, Vrije Universiteit, Amsterdam Percolation on high dimensional boxes and related questions

Alexander Fribergh, Université Lyon 1 Biased random walks on a Galton-Watson tree with leaves

Hsien-Kuei Hwang, Academia Sinica, Taipei A new analytic approach to the variance asymptotics of random digital trees

Andrzej Rucinski, Adam Mickiewicz University, Poznan Subhypergraph counts in random hypergraphs

Jonathon Peterson, University of Wisconsin, Madison Quenched limits for one-dimensional, transient, RWRE

Taral Guldahl Seierstad, University of Oslo The differential equation method and random graphs

Remco van der Hofstad, Eindhoven University of Technology First passage percolation on random graphs

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Vincent Beffara, UMPA-ENS, Lyon Isotropic embeddings of planar lattices

Tomasz Luczak, Adam Mickiewics University, Poznan Chasing robbers on random graphs Tatyana Turova, Lund University Asymptotics for the size of the largest component scaled to "log n" in inhomogeneous random graphs

Tom Sanders, Christ's College, Cambridge Probabilistic methods in additive combinatorics: sets with random spectrum

Ilkka Norros, VTT, Helsinki Power-law random graphs and routing problems

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Discrete Probability

Preprints 2009 spring

01 - Critical behavior in inhomogeneous random graphs - Remco van der Hofstad 02 - Poset limits and exchangeable random posets - Svante Janson 03 - Delange's Tauberian theorem and asymptotic normality of random ordered factorizations of integers - Hsien-Kuei Hwang, Svante Janson 04 - A mean-field approach to some Internet-like random networks - Ilkka Norros 05 - The diameter behavior in the random graph process - Tomasz Luczak, Taral Guldahl Seierstad 06 - A survey of dynamical percolation - Jeffrey Steif 07 - Asymptotic normality of statistics on permutation tableaux - Pawel Hitczenko, Svante Janson 08 - Triangle-duality and equality of infinitely many bond percolation thresholds - John Wierman, Robert Ziff 09 - Equality of bond percolation critical exponents for pairs of dual lattices - Matthew Sedlock, John Wierman 10 - Random graph asymptotics on high-dimensional tori. II. Volume, diameter and mixing time – Markus Heydenreich, Remco van der Hofstad 11 - Aperiodic non-isomorphic lattices with equivalent percolation and random- cluster models. - Klas Markström, John Wierman 12 - Probability asymptotics: notes on notation - Svante Janson 13 - Duality in inhomogeneous random graphs, and the cut metric - Svante Janson, Oliver Riordan 14 - Large cliques in a power-law random graph - Svante Janson, Tomasz Luczak, Ilkka Norros 15 - Susceptibility in inhomogeneous random graphs - Svante Janson, Oliver Riordan 16 - Current fluctuations of a system of one-dimensional random walks in random environment - Jonathon Peterson, Timo Seppäläinen 17 - Upper tails for counting objects in randomly induced subhypergraphs and rooted random graphs - Svante Janson, Andrzej Rucinski 18 - Dynamic random networks in dynamic populations - Tom Britton, Mathias Lindholm 19 - Quasi-random graphs and graph limits - Svante Janson 20 - A note on correlations in randomly oriented graphs - Svante Linusson 21 - Long and short paths in uniform random recursive dags - Luc Devroye, Svante Janson 22 - A counter-intuitive correlation in a random tournament - Sven Erick Alm, Svante Linusson

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23 - Correlations for paths in random orientations of G(n,p) - Sven Erick Alm, Svante Linusson 24 - On the speed of biased random walk in translation invariant percolation - Maria Deijfen, Olle Häggström 25 - Growing networks with preferential deletion and addition of edges - Maria Deijfen, Mathias Lindholm 26 - Diffusion approximation for the components in critical inhomogeneous random graphs of rank 1. - Tatyana Turova 27 - A functional combinatorial central limit theorem - Andrew Barbour, Svante Janson 28 - On the number of perfect matchings in random lifts - Catherine Greenhill, Svante Janson, Andrzej Rucinski 29 - Noise Correlation Bounds for Uniform Low Degree Functions - Per Austrin, Elchanan Mossel 30 - Dirac-type conditions for hamiltonian paths and cycles in 3-uniform hypergraphs - Vojtech Rödl, Andrzej Rucinski, Endre Szemeredi 31 - Threshold graph limits and random threshold graphs - , Susan Holmes, Svante Janson 32 - On the speed of coming down from infinity for $\X$-coalescent processes - Vlada Limic 33 - Finite-dimensional distributions for the size of the core in random graphs - Taral Seierstad 34 - Stronger large deviation bounds for Wormald's differential equation method - Taral Seierstad 35 - Perfect matchings and Hamilton cycles in hypergraphs with large degrees - Klas Markström, Andrzej Rucinski 36 - Susceptibility of random graphs with given vertex degrees - Svante Janson 37 - On Coupling and Convergence in Density and in Distribution - Hermann Thorisson

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Mathematical Logic: Set Theory and Model Theory

Report 2009 fall

We discuss some highlights of the semester program in the area of Set Theory. The program was very successful with significant progress achieved on the principal problems of the proposal. These problems included problems related to the metamathematics of the Continuum Hypothesis and problems at the frontier of the Inner Model Program.

The participants; D. Aspero, P. Larson, and J. Moore obtained a very nice result solving a decade old problem relating to the Continuum Hypothesis. The problem posed in 1999 2 concerned Π 2-maximality and the Continuum Hypothesis. The question asks whether there 2 are two Π 2-sentences each of which is Ω-consistent with the Continuum Hypothesis but which jointly refute the Continuum Hypothesis. One motivation for the question was the result of Woodin which showed that assuming there is a proper class of measurable Woodin 2 cardinals, then for the case of Σ 2-sentences the answer is no. The other motivation was the discovery of the Pmax-axiom and this was really the primary motivation.

2 Aspero-Larson-Moore answer this question for Π 2-sentences proving that there is such a 2 pair of Π 2-sentences. This result shows that the maximality property that characterizes the Pmax-axiom cannot be generalized to the Continuum Hypothesis. The result also places constraints on possible generalizations of the forcing axiom, Martin’s Maximum, to the context of CH.

Inspired by this result, Woodin showed that any such counterexample in the context of generic-◇ yields the nonexistence of inner models at the level of superstrong cardinals. While the failure of inner model theory at this level seems by current intuition extremely unlikely this result shows how a development in the technical theory of forcing could lead to such an unexpected theorem. Alternatively this result shows that the intuition from inner 2 model theory is that Π 2-maximality must be possible with generic- and this in turn suggests new directions for the technical theory of forcing in the context of forcing notions which do not add reals.

Another series of results obtained during the semester program concerned the focus problem: the fine-structure theory for one supercompact cardinal. Results obtained prior to the Mittag-Leffler program have identified the inner model problem for one supercompact cardinal as the key problem in extending inner model theory beyond the level of superstrong cardinals. The reason is that these results show that the generalization of Gödel’s Axiom of Constructibility to the level of exactly one supercompact cardinal yields a provably maximal version of this axiom. The existence of such an “ultimate” version of Gödel’s inner model L would have truly profound consequences in Set Theory and the foundations of Mathematics.

The generalizations of L to large cardinals are in the form of extender models. For large cardinals at the level of superstrong and below, the extenders are short extenders. The detailed theory of these models was worked out by Mitchell and Steel (both of whom were participants in the fall program) over 15 years ago. The extension of this theory beyond the level of superstrong cardinals requires the development of the theory of extender models involving long extenders. It has been realized for some time that dealing with long extenders creates serious technical problems. Results obtained during the fall program by Woodin have made significant progress on this problem yielding for the first time a

17 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS definition of fine-structural extender models with long extenders and generalizing significant elements of the Mitchell-Steel theory to the context of these new models. The theory is still at a preliminary stage and certain aspects could change but many key obstacles have been identified and overcome.

Quite a number of other results were obtained by the participants on a variety of topics in Set Theory. A very nice result was obtained by the two participants, Ilijas Farah and -non א Saharon Shelah, and shows that in ZFC any countable model has either 1 or 22 0 isomorphic ultrapowers associated with nonprincipal ultrafilters on N. The result also applies to separable metric structures, such as C*- algebras and II1 factors. Their results have already been submitted for publication. Farah also working with participants, P. McKenney and E. Schimmerling, proved that assuming the forcing axiom PFA then for every Hilbert space (even nonseparable), the automorphisms of the associated Calkin algebra are all inner. Ilijas Farah, Paul McKenney and Ernest Schimmerling discuss in the lecture room. Photo: M. Wiberg

In the area of constructive set theory and topos theory a group of people worked on Aczel- Myhill constructive set theory, CZF. Thomas Streicher together with Alex Simpson finished work on a sheaf model for CZF refuting both the power set axiom and unbounded separation. Extensions of CZF with axioms related to predicativity issues in formal topology, especially set-presentation of covers, were investigated by Benno van den Berg, Hajime Ishihara and Erik Palmgren. They studied in particular the set-generation scheme (SGS) and the principle for non-deterministic inductive definitions (NID) and their relation to relativized dependent choice and similar principles true in the standard type-theoretic model of CZF.

Topos theory and category-theoretic formulations of set theory were related topics of research. Van den Berg finalized a major paper with Ieke Moerdijk on sheaves in predicative algebraic set theory. Palmgren finished a paper relating Lawvere's categorical set theory and Bishop's informal theory of sets. Jaap van Oosten discovered that the effective topos contains at least part of a so-called Quillen model structure, which makes it possible to develop a homotopy theory in this topos. The appropriate notion of path is very much connected to the so-called "discrete reflection": the left adjoint to the inclusion of the discrete objects in the topos. It allows the discrete objects to be characterized as "having no nontrivial paths", and therefore (internally) the discrete reflection of an object as the set of its path components.

The graduate student-participant, Daisuke Ikegami, working with Woodin, obtained a likely solution to the problem of the relationship between determinacy and Blackwell determinacy at the level of real games. The main result is that the Axiom of Real Determinacy and the Axiom of Real Blackwell Determinacy are equivalent (in the context of the base theory ZF + DC). The details are still being checked but the proof looks quite promising.

Magidor and Väänänen finalized the solution of an old open problem concerning strong Löwenheim-Skolem properties and supercompact cardinals.

18 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

On the non-mathematical side a potluck party was organized every week and four special 20 person dinners were organized where the junior members could meet a senior member (Shelah, Magidor, Todorcevic and Woodin). These dinners were preceded by an informal question-and-answers session, and ended with a concert by the grand piano. Both the junior members and the senior mathematician in question alike reported that the arrangement was very successful and beneficial.

Vadim Kulikov plays guitar. In the front Professor and Mrs Magidor. Photo: J. Väänänen

Organizing committee Dag Normann, University of Oslo Erik Palmgren, University of Uppsala Jouko Väänänen, University of Helsinki and University of Amsterdam Hugh Woodin, University of California at Berkeley

On behalf of the organizing committee

Jouko Väänänen and Erik Palmgren

19 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Mathematical Logic: Set Theory and Model Theory

Participants 2009 fall

Name University City Arrival Departure Asperó, David Universitat de Barcelona Barcelona 5 Sep 20 Sep 1 Nov 14 Nov Bagaria, Joan Universitat de Barcelona Barcelona 1 Nov 29 Nov Baldwin, John University of Illinois Chicago 3 Sep 30 Oct Berg, van den, Benno TU Darmstadt Darmstadt 15 Oct 15 Dec Cummings, James Carnegie Mellon University Pittsburgh 15 Nov 16 Dec Di Prisco, Carlos IVIC Caracas 30 Oct 29 Nov Dobrinen, Natasha University of Denver 24 Nov 15 Dec Dzamonja, Mirna University of East Anglia Norwich 31 Aug 28 Sep Enayat, Ali American University Washington 31 Aug 1 Nov Engström, Fredrik Göteborg 1 Sep 13 Nov Farah, Ilias York University Toronto 1 Sep 30 Sep Flaskova, Jana University of West Bohemia Plzeń 2 Sep 16 Dec Galliani, Pietro University of Amsterdam Amsterdam 13 Nov 30 Nov Hedin, Anton Uppsala University Uppsala 15 Sep 15 Dec Hella, Lauri University of Tampere Tampere 20 Oct 15 Dec Hyttinen, Tapani University of Helsinki Helsinki 5 Oct 30 Oct Ikegami, Daisuke Universiteit van Amsterdam Amsterdam 4 Sep 15 Dec Japan Advanded Institute of Ishihara, Hajime Ishikawa 13 Nov 1 Dec Science and Technology Alfréd Rényi Institut of Juhász, István Budapest 31 Aug 30 Sep Mathematics Kangas, Kaisa University of Helsinki Helsinki 26 Oct 1 Nov Kankaanpää, Teppo Helsinki University Helsinki 5 Oct 15 Dec California Institute of Kechris, Alexander Pasadena 1 Sep 30 Sep Technology Kennedy, Juliette University of Helsinki Helsinki 27 Aug 15 Dec Keskinen, Lauri Universiteit van Amsterdam Amsterdam 1 Sep 15 Dec Kesälä, Meeri University of Helsinki Helsinki 15 Oct 15 Nov Rheinische-Friedrich-Wilhelm- Koepke , Peter Bonn 1 Dec 14 Dec Universität Koerwien, Martin University of Illinois Chicago 18 Oct 31 Oct Kojman, Menachem Ben Gurion University Be'er-Sheva 1 Sep 12 Sep Kontinen, Juha University of Helsinki Helsinki 2 Nov 4 Dec Koponen, Vera University of Uppsala Uppsala 1 Sep 15 Dec Kossak, Roman The Graduate Center New York 1 Sep 15 Dec Kulikov, Vadim Helsinki University Helsinki 1 Sep 15 Dec Larson, Paul Miami University Oxford, Ohio 1 Sep 15 Oct Lindström, Ingrid Uppsala University Uppsala 1 Sep 15 Dec Lopez-Abad, Jordi ICMAT (CSIC) Madrid 1 Dec 13 Dec Loukanova, Roussanka Uppsala University Uppsala 1 Sep 15 Dec Luosto, Kerkko University of Helsinki Helsinki 1 Sep 15 Dec

20 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Magidor, Menachem The Hebrew University Jerusalem 1 Sep 15 Dec Martin-Löf, Per Stockholms universitet Stockholm 1 Sep 15 Dec McKenney, Paul Carnegie Mellon University Pittsburgh 1 Sep 30 Sep Mildenberger, Heike The Hebrew University Jerusalem 15 Nov 15 Dec Mitchell, William University of Florida Gainesville 12 Oct 15 Dec Moore, Justin Cornell University Ithaca 1 Sep 30 Sep Normann, Dag University of Oslo Oslo 5 Oct 9 Oct Oosten, van, Jaap University of Utrecht Utrecht 30 Sep 14 Dec Palmgren, Erik Uppsala University Uppsala 1 Sep 15 Dec Sabok, Marcin Wroclaw University Wroclaw 1 Sep 15 Dec Schimmerling, Ernest Carnegie Mellon University Pittsburgh 1 Sep 30 Sep Schindler, Ralf Universität Münster Münster 14 Sep 5 Nov Schlicht, Philipp Friedrich-Wilhelms-Universität Bonn 31 Aug 16 Dec Shelah, Saharon Hebrew University Jerusalem 1 Sep 30 Sep Steel, John University of California Berkeley 1 Sep 30 Sep Stoltenberg, Viggo Uppsala University Uppsala 5 Oct 31 Oct Streicher, Thomas Technische Universität Darmstadt 20 Sep 9 Oct Todorcevic, Stevo University of Toronto Toronto 1 Sep 15 Dec Tuomi, Lauri University of Helsinki Helsinki 21 Oct 31 Oct Velickovic, Boban Université Paris 7 Paris 3 Oct 31 Oct Universidad Nacional de Villaveces, Andrés Bogotá 1 Oct 15 Nov Colombia Vlitas, Dimitrios University of Toronto Toronto 26 Nov 6 Dec University of Helsinki and Helsinki and Väänänen, Jouko 27 Aug 15 Dec Amsterdam Amsterdam Walczak-Typke, Agatha University of Vienna Vienna 31 Aug 15 Dec Wilander, Olov Uppsala University Uppsala 1 Oct 15 Dec Wohofsky, Wolfgang Vienna University of Technology Vienna 14 Sep 27 Sep Woodin, Hugh University of California Berkeley Berkeley 9 Sep 12 Dec Yang, Fan University of Helsinki Helsinki 2 Nov 13 Nov Universidad Nacional de Zambrano, Pedro Bogotà 1 Oct 16 Oct Colombia

21 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Mathematical Logic: Set theory and model theory

Seminars 2009 fall

Stevo Todorcevic, University of Toronto gave a series of 4 lectures with the title: A basis problem for compact spaces

Jouko Väänänen, Universitites of Helsinki and of Amsterdam gave a series of 5 lectures with the title: Set theory and logic

Erik Palmgren, Uppsala University Constructivist and structuralist foundations: Bishop's and Lawvere's theories of sets

Bill Mitchell, University of Florida, Gainesville The covering lemma: 35 years, and a question

Heike Mildenberger, Universität Wien Filters versus semifilters

James Cummings, Carnegie Mellon University, Pittsburgh Recent uses of infinitary methods in finite combinatorics

Jean Larson, Gainesville, Florida Scattered thoughts on infinite combinatorics

Hajime Ishihara, Japan Advanced Institute of Science and Technology, Ishikawa A boundedness principle in constructive reverse mathematics Vera Koponen, University of Uppsala Asymptotic probabilities of extension axioms.

Kerkko Luosto, University of Helsinki Combinatorics of quantifiers

Joan Bagaria, Universitat de Barcelona Large cardinals and accessible categories

Philipp Schlicht, Friedrich-Wilhelm-Universität, Bonn Descriptive set theory at uncountable cardinals

Lauri Hella, University of Tampere Monadic sigma-1-1 and modal logic with quantified binary relations

Juha Kontinen, University of Helsinki Regular representations of uniform TC0.

Agatha Walczak-Typke, University of Vienna Constructibility of potentially isomorphic pairs vs classification in homogeneous model theory.

22 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Carlos Di Prisco, IVIC, Caracas Graphs defined by the shift operation

Ralf Schindler, Universität Münster Woodin's axiom (*), bounded forcing axioms, and related issues. Part II

Daisuke Ikegami, Universiteit van Amsterdam Blackwell determinacy

Meeri Kesälä, University of Helsinki Finitary abstract elementary classes

Fredrik Engström, University of Gothenburg Logical constants and invariance

Menachem Magidor, the Hebrew University, Jerusalem The Lowenheim-Skolem-Tarski number of the Hartig-quantifier can be the first inaccessible

Benno van den Berg, TU Darmstadt An introduction to algebraic set theory

Tapani Hyttinen, University of Helsinki Model theory and metric structures

Vadim Kulikov. University of Helsinki Equivalence relations on a generalized Baire space

Boban Velickovic, Université Paris 7 Universal countable Borel equivalence relations

Andrés Villaveces, Universidad Nacional de Colombia, Bogota Dependence outside first order contexts

Dag Normann, University of Oslo The sequential functionals are far from being algebraic domains

Jaap van Oosten, University of Utrecht Constructions of (order-) partial combinatory algebras

Hugh Woodin, University of California, Berkeley Pi-2-2 -maximality and generic diamond

Ralf Schindler, Universität Münster Woodin's axiom (*), bounded forcing axioms, and related issues.

Jana Flaskova, University of West Bohemia, Plzeń Some ultrafilters on natural numbers

Thomas Streicher, Technische Universität Darmstadt Sheaf models for CZF refuting power set and full separation

Roman Kossak, City University of New York Classification problems in models of Peano arithmetic

23 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Marcin Sabok, Wroclaw University Playing with idealized forcing

Paul Larson, Miami University, Ohio Universally measurable sets in generic extensions

Justin Moore, Cornell University, Ithaca CH and the combinatorics of the club filter

Saharon Shelah, Hebrew University and Rutgers University An advance on the existence of completely separable MAD families

Ali Enayat, American University, Washington DC Automorphisms of Models of Set Theory

Alexander Kechris, CALTECH, Pasadena The complexity of classification problems in ergodic theory.

Istvan Juhasz, Hungarian Academy of Sciences, Budapest On the convergence and character spectra of compact spaces

John Baldwin, University of Illinois, Chicago Shelah´s Conjecture: The Universe is Wide or Deep

Ilijas Farah, York University, Toronto Model theory of operator algebras (joint work with Bradd Hart and David Sherman)

24 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Mathematical Logic: Set theory and model theory

Preprints 2009 fall

01 - CH, a problem of Rolewicz and bidiscrete systems - Mirna Džamonja, István Juhász 02 - Measurable chromatic and independence numbers for ergodic graphs and group actions - Alexander S. Kechris, Clinton T. Conley 03 - A dichotomy for the number of ultrapowers - Ilijas Farah, Saharon Shelah 04 - Constructivist and Structuralist Foundations: Bishop's and Lawvere's Theories of Sets - Erik Palmgren 05 - Woodin's axiom (*), bounded forcing axioms, and precipitous ideals on $\omega_1$ - Ralf Schindler 06 - Aspects of Predicative Algebraic Set Theory III: Sheaves - Benno van den Berg, Ieke Moerdijk 07 - An Improper Arithmetically Closed Borel Subalgebra of P(omega) mod FIN - Ali Enayat, Saharon Shelah 08 - On cofinal submodels and first interstices - Roman Kossak 09 - The Stability Spectrum for Classes of Atomic models - John Baldwin, Saharon Shelah 10 - Interpreting Groups and Fields in Simple, Finitary AECs - Tapani Hyttinen, Meeri Kesälä 11 - Forcing properties of ideals of closed sets - Marcin Sabok, Jindrich Zapletal 12 - Amalgamation, Absoluteness, and Categoricity - John Baldwin 13 - Rapid ultrafilters and summable ideals - Jana Flaskova 14 - Tukey types of ultrafilters - Natasha Dobrinen, Stevo Todorcevic 15 - On Löwenheim-Skolem-Tarski numbers for extensions of first order logic - Menachem Magidor, Jouko Väänänen 16 - Model Theoretic Perspectives on the Philosophy of Mathematics - John Baldwin 17 - Asymptotic probabilities of extension properties - Vera Koponen 18 - Generic Banach spaces and generic simplexes - Jordi Lopez-Abad, Stevo Todorcevic 19 - Lascar types and Lascar automorphisms in Abstract Elementary Classes - Tapani Hyttinen, Meeri Kesälä 20 - Countable Ideals Models for CZF - Alex Simpson, Thomas Streicher 21 - Martin's maximum and weak square - James Cummings, Menachem Magidor 22 - A Remark on Negation in Dependence Logic - Juha Kontinen, Jouko Väänänen 23 - Non-permutation invariant Borel quantifiers - Fredrik Engström, Philipp Schlicht 24 - A Notion of Homotopy for the Effective Topos - Jaap van Oosten 25 - Regular Representations of Uniform $TC^0$ - Lauri Hella, Juha Kontinen, Kerkko Luosto 26 - $C^{(n)}$-Cardinals - Joan Bagaria 27 - Notions of Independence for Metric Abstract Elementary Classes – Andrés Villaveces, Pedro Zambrano 28 - On Milliken-Taylor Ultrafilters - Heike Mildenberger 29 - Remarks on Gaps in Dense(Q)/nwd - Teppo Kankaanpää 30 - Potential Isomorphism of Elementary Substructures of a Homogeneous Model - Agatha Walczak-Typke, Tapani Hyttinen, Sy-David Friedman

25 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

31 - A Hanf Number for Satuation and Omission - John Baldwin, Saharon Shelah 32 - Real Determinacy and Real Blackwell Determinacy - Daisuke Ikegami, W. Hugh Woodin 33 - Around Superstability in Metric Abstract Elementary Classes: Limit Models and r-Towers - Andrés Villaveces, Pedro Zambrano 34 - On Ajtai Hypothesis in different cardinalities - Lauri Keskinen 35 - The relation of rapid ultrafilters and Q-points to van der Waerden ideal - Jana Flaskova 36 - Remarks on the relation between families of setoids and identity in type theory - Erik Palmgren 37 - On the maximal resolvability of monotonically normal spaces - Istvan Juhasz, Menachem Magidor 38 - On $\Pi_2$-maximality and the Continuum Hypothesis - David Asperó, Paul Larson, Justin Tatch Moore

26 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Participants from the Nordic countries

Finland Hella, Lauri, Tampere Hyttinen, Tapani, Helsinki Kangas, Kaisa, Helsinki Kankaanpää, Teppo, Helsinki Kennedy, Juliette, Helsinki Kesälä, Meeri, Helsinki Keskinen, Lauri, Helsinki Kontinen, Juha, Helsinki Kulikov, Vadim, Helsinki Luosto, Kerkko, Helsinki Norros, Ilkka, Helsinki Tuomi, Lauri, Helsinki Väänänen, Jouko, Helsinki & Amsterdam

Norway Normann, Dag, Oslo Seierstad, Taral, Oslo

Sweden Alm, Sven Erick, Uppsala Lagerås, Andreas, Stockholm Austrin, Per, Stockholm Lindholm, Mattias, Stockholm Björnberg, Jakob, Stockholm Lindström, Ingrid, Uppsala Britton, Tom, Stockholm Linusson, Svante, Stockholm Broman, Erik, Göteborg Markström, Klas, Umeå Deijfen, Maria, Stockholm Martin-Löf, Anders, Stockholm Engström, Fredrik, Göteborg Martin-Löf, Per, Stockholm Eriksson, Kimmo, Västerås Nordenstam, Eric, Stockholm Hedin, Anton, Uppsala Palmgren, Erik, Uppsala Hegarty, Peter, Göteborg Renlund, Henrik, Uppsala Holmgren, Cecilia, Uppsala Steif, Jeff, Göteborg Holst, Lars, Stockholm Stoltenberg,Viggo, Uppsala Häggström, Olle, Göteborg Söderberg, Bo, Lund Janson,Svante, Uppsala Turova, Tatyana, Lund Johansson, Anders, Gävle Tykesson, Johan, Göteborg Johansson, Fredrik, Stockholm Vallier, Thomas, Lund Johansson, Kurt, Stockholm Warfheimer, Marcus, Göteborg Jonasson, Johan, Göteborg Wilander, Olov, Uppsala Koponen, Vera, Uppsala Wästlund, Johan, Göteborg

27 Publications

Institut Mittag-Leffler publishes two research journals. Acta Mathematica was founded by Gösta Mittag-Leffler in 1882, while Arkiv för matematik traces its roots back to a journal founded in 1903 by the Royal Swedish Academy of Sciences.

Since January 1, 2006 Springer is handling printing, subscriptions and distribution of both journals. Naturally, the Institute retains full ownership and full editorial control of the journals. All back volumes of both journals have been digitized by Springer and are available on the web for subscribers.

Acta Mathematica 2 volumes/year (4 issues, totally 600 pp) During 2009 the issues 202:1-2 and 203:1-2 have appeared with in total 11 articles.

The influx of manuscripts has been very good.

Printed version: 474 copies Electronic version: 5 547 subscribers via consortia of universities all over the world. In this way the journal is reached by 34 African, 1 119 American, 1 313 Australasian and 3 081 European departments and institutions at different universities.

Editorial Board: Anders Björner, Editor-in-Chief, Institut Mittag-Leffler Karsten Grove, Dept of Mathematics, University of Notre Dame, USA; Jens Carsten Jantzen, University of Aarhus, Denmark; Kurt Johansson, Dept of Mathematics, The Royal Institute of Technology, KTH, Stockholm, Sweden; Pekka Koskela, Dept of Mathematics and Statistics, University of Jyväskylä, Finland; Kristian Seip, Dept of Mathematical Sciences, NTNU, Trondheim, Norway; Johannes Sjöstrand, IMB, Université de Bourgogne, Dijon, France

Technical Editors: Anders Björn, Dept of Mathematics, Linköping University, Sweden; Federico Incitti, Dept of Mathematics, Sapienza University of Rome, Italy.

Editorial Assistant: Margareta Wiberg Roland, Institut Mittag-Leffler

28 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Arkiv för matematik 1 volume/year (2 issues, totally 400 pp) The issues 46:1-2 have appeared during 2009 with in total 19 articles.

The influx of manuscripts has been sufficient, but could be better.

Printed version: 215 copies Electronic version: 5 050 subscribers via consortia of universities all over the world. In this way the journal is reached by 34 African, 899 American, 1 047 Australasian and 3 070 European departments and institutions at different universities.

Editorial Board: Anders Björner, Editor-in-Chief, Institut Mittag-Leffler Ralf Fröberg, Dept of Mathematics, Stockholm University, Sweden; Olle Häggström, Dept of Mathematical Sciences, Chalmers University of Technology, Göteborg, Sweden – 2009-06-30 Ari Laptev, Dept of Mathematics, The Royal Institute of Technology, KTH, Stockholm, Sweden; Mikael Passare, Dept of Mathematics, Stockholm University, Sweden Peter Sjögren, Dept of Mathematics, Göteborg University, Sweden; Jeffrey Steif, Dept of Mathematical Sciences, Chalmers University of Technology, Göteborg, Sweden 2009-07-01 –

Technical Editor: Anders Björn, Dept of Mathematics, Linköping University, Sweden

Editorial Assistant: Margareta Wiberg Roland, Institut Mittag-Leffler

29 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

The board of Institut Mittag-Leffler 2009

Bo Berndtsson, Chalmers University of Technology, CTH, Göteborg Anders Björner, Director, Institut Mittag-Leffler Torsten Ekedahl, Stockholm University Olle Häggström, Chalmers University of Technology, CTH, Göteborg Bjørn Jahren, University of Oslo, Vice Chairman Svante Janson, Uppsala University Kurt Johansson, Royal Institute of Technology, KTH, Stockholm Jan-Erik Roos, Stockholm University, Chairman Mikael Rørdam, Copenhagen, 2009-07-01 – Eero Saksman, University of Helsinki Jan Philip Solovej, H.C. Ørsted Institute, Copenhagen, Vice Chairman, – 2009-06-30 Anders Szepessy, Royal Institute of Technology, KTH, Stockholm Hermann Thorisson, University of Iceland, Reykjavik Hans Wallin, Umeå University

Board meeting November 2009. From left standing: A. Szepessy, H. Wallin, Lisbeth Wallin and Gunnar Öquist, The Royal Swedish Academy of Sciences, T. Ekedahl, B. Jahren, S. Janson, J.-E. Roos, O. Häggström, E. Saksman. Sitting: H. Thorisson, J.-P. Solovej, K. Johansson and A. Björner. Photo: M. Wiberg Roland

30 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Administrative information 2009

Staff Anders Björner Director, 60% Federico Incitti Technical editor, 50% Alexander Koponen Computer technician, 80% Marie-Louise Koskull Administrator of the scientific program Fawzi Mourou Caretaker Mikael Rågstedt Librarian Margareta Wiberg Roland Head of administration and economy

Fawzi Mourou, Alexander Koponen, Marie-Louise Koskull, Margareta Wiberg Roland, Anders Björner and Mikael Rågstedt. Photo: C. Ameln

Research program During 2009 the Institute hosted 151 visiting researchers, who together spent 272.5 man- months working at the Institute.

Library and historical archive The library subscribes to several electronic journals and to around 110 print journals. In addition, we receive some 70 journals in exchange for Acta Mathematica and Arkiv för matematik.

Information and copies from the historical archive are frequently requested, including visits by mathematical historians.

31 INSTITUT MITTAG-LEFLER – A NORDIC INSTITUT FOR RESEARCH IN MATHEMATICS

Financial statement (kSEK)

Result 2009 Result 2008 Income Contributions from Nordic countries 1 067 787 Contribution from the Swedish Research Council 1 100 1 105 Grant Income 1 260 1 029 Other Income 592 737 Total External Income 4 019 3 657 Journals net 495 718 Profit available for distribution from the Endowment 2 974 3 344 Exceeded withdrawal from the Endowment 1 069 806 Total Income 8 558 8 525

Expenditure Scientific Program - Grants 1 582 1 888 Offices and Lodging 2 256 1 938 Library 1 516 1 519 Administration 3 203 3 180 Total Costs 8 558 8 525

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