Events

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Monday, 27 February
Time Speaker Title Location
15:15 - 16:30 Claire Voisin
Jussieu and ITS
Symplectic Geometry Seminar
Hyper-Kähler manifolds and their moduli
HG G 43 
Tuesday, 28 February
Time Speaker Title Location
11:15 - 12:00 Po-Ling Loh
University of Wisconsin-Madison
Research Seminar in Statistics
Influence maximization in stochastic and adversarial settings 
HG  G 19.1 
Abstract: We consider the problem of influence maximization in fixed networks, for both stochastic and adversarial contagion models. In the stochastic setting, nodes are infected in waves according to linear threshold or independent cascade models. We establish upper and lower bounds for the influence of a subset of nodes in the network, where the influence is defined as the expected number of infected nodes at the conclusion of the epidemic. We quantify the gap between our upper and lower bounds in the case of the linear threshold model and illustrate the gains of our upper bounds for independent cascade models in relation to existing results. Importantly, our lower bounds are monotonic and submodular, implying that a greedy algorithm for influence maximization is guaranteed to produce a maximizer within a 1-1/e factor of the truth. In the adversarial setting, an adversary is allowed to specify the edges through which contagion may spread, and the player chooses sets of nodes to infect in successive rounds. We establish upper and lower bounds on the pseudo-regret for possibly stochastic strategies of the adversary and player. This is joint work with Justin Khim and Varun Jog.
17:15 - 18:15 Alessio Figalli

Inaugural Lectures
Optimal Transport: Theory and Applications
HG F 30 
Wednesday, 1 March
Time Speaker Title Location
13:30 - 15:00 Dr. Hyenho Lho
ETH Zürich
Algebraic Geometry and Moduli Seminar
GW/SQ wall crossing II 
HG G 43 
Abstract: We will study the wall crossing formula between Gromov-Witten invariant and Stable Quotient invariant for all genus. This formula which is recently proved for very general cases by Ciocan-Fontanine and Kim cover a large class of target spaces. In series of lectures, we will study this formula eventually enlarging the class of target spaces from Fano to Calabi-Yau.
15:45 - 16:45 Fanny Kassel
CNRS - IHES
Geometry Seminar
Proper affine actions of right-angled Coxeter groups  
HG G 43 
Abstract: The Auslander Conjecture states that all discrete groups acting properly and cocompactly on R^n by affine transformations should be virtually solvable. In 1983, Margulis constructed the first examples of proper (but not cocompact) affine actions of nonabelian free groups. It seems that until now all known examples of irreducible proper affine actions were by virtually solvable or virtually free groups. I will explain that any right-angled Coxeter group on k generators admits a proper affine action on R^{k(k-1)/2}. This is joint work with J. Danciger and F. Guéritaud.
17:15 - 19:00 Alessandra Caraceni
University of Bath
Seminar on Stochastic Processes
Self-Avoiding Walks on Random Quadrangulations 
Y27  H 25
Abstract: The local limit of random quadrangulations (UIPQ) and the local limit of quadrangulations with a simple boundary (the simple boundary UIHPQ) are two very well studied objects. We shall see how the simple boundary UIHPQ relates to an annealed model of self-avoiding walk on random quadrangulations, and how metric information obtained for the UIHPQ can be used to study quantities such as the displacement of the self-avoiding walk from the origin, as well as to ultimately investigate how the biasing of random quadrangulations by the number of their self-avoiding walks affects their local limit.
Thursday, 2 March
Time Speaker Title Location
15:15 - 16:15 Alexander Veselov
Loughborough University
Talks in Mathematical Physics
Lyapunov spectrum for Markov dynamics and hyperbolic structures 
HG G 43 
Abstract: We study the Lyapunov exponents Λ(x) for Markov dynamics as a function of path determined by x ∈ RP1 on a binary planar tree, describing the growth of Markov triples and their ``tropical" version - Euclid triples. We show that the corresponding Lyapunov spectrum is [0, ln φ], where φ is the golden ratio, and prove that on the set X of the most irrational numbers the corresponding function ΛX is convex and strictly monotonic. The key step is using the relation of Markov numbers with hyperbolic structures on punctured torus, going back to D. Gorshkov and H. Cohn, and, more precisely, the recent result by V. Fock, who combined this with Thurston’s lamination ideas. The talk is based on joint work with K. Spalding.
16:15 - 17:00 Ben Marwick
University of Washington, Seattle
ZüKoSt Zürcher Kolloquium über Statistik
Reproducible Research Compendia via R packages 
HG G 19.1 
Abstract: "Long considered an axiom of science, the reproducibility of scientific research has recently come under scrutiny after some highly-publicized failures to reproduce results. This has often been linked to the failure of the current model of journal publishing to provide enough details for reviewers to adequately assess the correctness of papers submitted for publication. One early proposal for ameliorating this situation is to bundle the different files that make up a research result into a publicly-available 'compendium'. At the time it was originally proposed, creating a compendium was a complex process. In this talk I show how modern software tools and services have substantially lightened the burden of making compendia. I describe current approaches to making these compendia to accompany journal articles. Several recent projects of varying sizes are briefly presented to show how my colleagues and I are using R and related tools (e.g. version control, continuous integration, containers, repositories) to make compendia for our publications. I explain how these approaches, which we believe to be widely applicable to many types of research work, subvert the constraints of the typical journal article, and improve the efficiency and reproducibility of our research."
17:15 - 18:15 Anthony Réveillac 
INSA de Toulouse
Talks in Financial and Insurance Mathematics
A Black-Scholes type formula for the pricing of some reinsurance contract 
HG G 43 
Abstract: In this talk we will derive, using the Malliavin calculus, a new formula which can be thought as a counterpart for some reinsurance contracts of the celebrated Black-Scholes formula in Finance. Our approach allows one for instance to consider claims that may depend on the intensity of the underlying counting process defining the risk process. This constitutes a joint work with Caroline Hillairet (ENSAE - Paris) and Ying Jiao (ISFA - Lyon).
17:15 - 18:15 Alessandro Carlotto

Inaugural Lectures
Isolated gravitational systems: four centuries of mathematical challenges
HG F 30 
Friday, 3 March
Time Speaker Title Location
16:00 - 17:15 Pierrick Bousseau
Imperial College London
Algebraic Geometry and Moduli Seminar
DT invariants from holomorphic curves 
HG G 43 
Abstract: I will first describe a general analogy between DT invariants of 3-Calabi-Yau categories and holomorphic disks in holomorphic symplectic varieties, and reinterpret the Gromov-Witten/Kronecker correspondence in this context. In some specific case, I will then explain a conjectural extension of this result relating refined DT invariants and holomorphic curves of higher genus. Finally, I plan to give a sketch of proof of this extended correspondence.

Next week 

 
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27.02.2017
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