Minkowski space of dimension 2+1 is the Lorentzian analogue of Euclidean 3-space. It is well-known that there exists an isometric embedding of the hyperbolic plane in Minkowski space, which is the analogue of the embedding of the round sphere in Euclidean space. However, differently from the Euclidean case, the embedding of the hyperbolic plane is not unique up to global isometries. In this talk I will discuss several results on the classification of these embeddings, and explain how this problem is related to Monge-Ampère equations, harmonic maps, and Teichmüller theory. This is joint work with Francesco Bonsante and Peter Smillie.

Hitchin representations are an important class of representations of fundamental groups of closed hyperbolic surfaces into PSL(n,R), at the heart of higher Teichmüller theory. Given such a representation j, there is a unique j-equivariant harmonic map from the universal cover of the hyperbolic surface to the symmetric space of PSL(n,R). We show that its energy density is at least 1 and that rigidity holds. In particular, we show that given a Hitchin representation, every equivariant minimal immersion from the hyperbolic plane into the symmetric space of PSL(n,R) is distance-increasing. Moreover, equality holds at one point if and only if it holds everywhere and the given Hitchin representation j is an n-Fuchsian representation.

I shall report about a new direct construction of Nori motives, discovered independently by Barbieri-Viale and Prest on the one hand, by Joyal and myself on the other hand. Unlike previous constructions, one uses only standard constructions in category theory, like Frey free abelian category on a given additive category, and Serre’s construction of quotient categories.

The statistical measure Evolutionary Entropy characterizes Darwinian Fitness and predicts the outcome of competition for limited resources between related entities at various levels of organization: metabolic, cellular, organismic and social. I will discuss the mathematical basis of the selection principle and describe its application to the evolution of aging and the origin of age-related diseases.

 

Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained.

 

Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as o-minimal geometry, has for prototype real semi-algebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity.

 

The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on o-minimal structures and their tameness properties, I will discuss:
– the use of tame geometry in proving algebraization results (Pila-Wilkie theorem; o-minimal Chow and GAGA theorems in definable complex analytic geometry);
– the tameness of period maps; algebraicity of images of period maps;
– functional transcendence results: Ax-Schanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (André-Oort conjecture and Zilber-Pink conjecture);
– the geometry of Hodge loci and their closures.

 

 

Hodge theory, as developed by Deligne and Griffiths, is the main tool for analyzing the geometry and arithmetic of complex algebraic varieties. It is an essential fact that at heart, Hodge theory is NOT algebraic. On the other hand, according to both the Hodge conjecture and the Grothendieck period conjecture, this transcendence is severely constrained.

 

Tame geometry, whose idea was introduced by Grothendieck in the 80s, seems a natural setting for understanding these constraints. Tame geometry, developed by model theorists as o-minimal geometry, has for prototype real semi-algebraic geometry, but is much richer. It studies structures where every definable set has a finite geometric complexity.

 

The aim of this course is to present a number of recent applications of tame geometry to several problems related to Hodge theory and periods. After recalling basics on o-minimal structures and their tameness properties, I will discuss:
– the use of tame geometry in proving algebraization results (Pila-Wilkie theorem; o-minimal Chow and GAGA theorems in definable complex analytic geometry);
– the tameness of period maps; algebraicity of images of period maps;
– functional transcendence results: Ax-Schanuel conjecture from abelian varieties to Shimura varieties and variations of Hodge structures. Applications to atypical intersections (André-Oort conjecture and Zilber-Pink conjecture);
– the geometry of Hodge loci and their closures.

 

——–  IMPORTANT INFORMATION  ——–

Due to the health situation related to the Coronavirus epidemic, the course has been cancelled and postponed at a later date to be confirmed.

In physics, the renormalisation group provides a powerful point of view to understand random systems with strong correlations. Despite advances in a number of particular problems, in general its mathematical justification remains a holy grail. I will give an introduction to the main concepts from the point of view of a mathematician and illustrate its use in some examples.

——–  IMPORTANT INFORMATION  ——–

Due to the health situation related to the Coronavirus epidemic, the course has been cancelled and postponed at a later date to be confirmed.

In physics, the renormalisation group provides a powerful point of view to understand random systems with strong correlations. Despite advances in a number of particular problems, in general its mathematical justification remains a holy grail. I will give an introduction to the main concepts from the point of view of a mathematician and illustrate its use in some examples.

——–  IMPORTANT INFORMATION  ——–

Due to the health situation related to the Coronavirus epidemic, the course has been cancelled and postponed at a later date to be confirmed.

In physics, the renormalisation group provides a powerful point of view to understand random systems with strong correlations. Despite advances in a number of particular problems, in general its mathematical justification remains a holy grail. I will give an introduction to the main concepts from the point of view of a mathematician and illustrate its use in some examples.

——–  IMPORTANT INFORMATION  ——–

Due to the health situation related to the Coronavirus epidemic, the course has been cancelled and postponed at a later date to be confirmed.

In physics, the renormalisation group provides a powerful point of view to understand random systems with strong correlations. Despite advances in a number of particular problems, in general its mathematical justification remains a holy grail. I will give an introduction to the main concepts from the point of view of a mathematician and illustrate its use in some examples.

In these lectures we will present the mathematical proofs of conformal invariance of a number of models coming from planar statistical mechanics, including the Ising and dimer models. In particular, we will explain how discrete notions of holomorphicity can be used to solve discrete versions of classical Boundary Value Problems, and how this analysis is related to conformal invariance of certain observables in planar statistical mechanics.

In these lectures we will present the mathematical proofs of conformal invariance of a number of models coming from planar statistical mechanics, including the Ising and dimer models. In particular, we will explain how discrete notions of holomorphicity can be used to solve discrete versions of classical Boundary Value Problems, and how this analysis is related to conformal invariance of certain observables in planar statistical mechanics.