Project acronym AMAREC
Project Amenability, Approximation and Reconstruction
Researcher (PI) Wilhelm WINTER
Host Institution (HI) WESTFAELISCHE WILHELMS-UNIVERSITAET MUENSTER
Call Details Advanced Grant (AdG), PE1, ERC-2018-ADG
Summary Algebras of operators on Hilbert spaces were originally introduced as the right framework for the mathematical description of quantum mechanics. In modern mathematics the scope has much broadened due to the highly versatile nature of operator algebras. They are particularly useful in the analysis of groups and their actions. Amenability is a finiteness property which occurs in many different contexts and which can be characterised in many different ways. We will analyse amenability in terms of approximation properties, in the frameworks of abstract C*-algebras, of topological dynamical systems, and of discrete groups. Such approximation properties will serve as bridging devices between these setups, and they will be used to systematically recover geometric information about the underlying structures. When passing from groups, and more generally from dynamical systems, to operator algebras, one loses information, but one gains new tools to isolate and analyse pertinent properties of the underlying structure. We will mostly be interested in the topological setting, and in the associated C*-algebras. Amenability of groups or of dynamical systems then translates into the completely positive approximation property. Systems of completely positive approximations store all the essential data about a C*-algebra, and sometimes one can arrange the systems so that one can directly read of such information. For transformation group C*-algebras, one can achieve this by using approximation properties of the underlying dynamics. To some extent one can even go back, and extract dynamical approximation properties from completely positive approximations of the C*-algebra. This interplay between approximation properties in topological dynamics and in noncommutative topology carries a surprisingly rich structure. It connects directly to the heart of the classification problem for nuclear C*-algebras on the one hand, and to central open questions on amenable dynamics on the other.
Summary
Algebras of operators on Hilbert spaces were originally introduced as the right framework for the mathematical description of quantum mechanics. In modern mathematics the scope has much broadened due to the highly versatile nature of operator algebras. They are particularly useful in the analysis of groups and their actions. Amenability is a finiteness property which occurs in many different contexts and which can be characterised in many different ways. We will analyse amenability in terms of approximation properties, in the frameworks of abstract C*-algebras, of topological dynamical systems, and of discrete groups. Such approximation properties will serve as bridging devices between these setups, and they will be used to systematically recover geometric information about the underlying structures. When passing from groups, and more generally from dynamical systems, to operator algebras, one loses information, but one gains new tools to isolate and analyse pertinent properties of the underlying structure. We will mostly be interested in the topological setting, and in the associated C*-algebras. Amenability of groups or of dynamical systems then translates into the completely positive approximation property. Systems of completely positive approximations store all the essential data about a C*-algebra, and sometimes one can arrange the systems so that one can directly read of such information. For transformation group C*-algebras, one can achieve this by using approximation properties of the underlying dynamics. To some extent one can even go back, and extract dynamical approximation properties from completely positive approximations of the C*-algebra. This interplay between approximation properties in topological dynamics and in noncommutative topology carries a surprisingly rich structure. It connects directly to the heart of the classification problem for nuclear C*-algebras on the one hand, and to central open questions on amenable dynamics on the other.
Max ERC Funding
1 596 017 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym BeyondA1
Project Set theory beyond the first uncountable cardinal
Researcher (PI) Assaf Shmuel Rinot
Host Institution (HI) BAR ILAN UNIVERSITY
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary We propose to establish a research group that will unveil the combinatorial nature of the second uncountable cardinal. This includes its Ramsey-theoretic, order-theoretic, graph-theoretic and topological features. Among others, we will be directly addressing fundamental problems due to Erdos, Rado, Galvin, and Shelah.
While some of these problems are old and well-known, an unexpected series of breakthroughs from the last three years suggest that now is a promising point in time to carry out such a project. Indeed, through a short period, four previously unattainable problems concerning the second uncountable cardinal were successfully tackled: Aspero on a club-guessing problem of Shelah, Krueger on the club-isomorphism problem for Aronszajn trees, Neeman on the isomorphism problem for dense sets of reals, and the PI on the Souslin problem. Each of these results was obtained through the development of a completely new technical framework, and these frameworks could now pave the way for the solution of some major open questions.
A goal of the highest risk in this project is the discovery of a consistent (possibly, parameterized) forcing axiom that will (preferably, simultaneously) provide structure theorems for stationary sets, linearly ordered sets, trees, graphs, and partition relations, as well as the refutation of various forms of club-guessing principles, all at the level of the second uncountable cardinal. In comparison, at the level of the first uncountable cardinal, a forcing axiom due to Foreman, Magidor and Shelah achieves exactly that.
To approach our goals, the proposed project is divided into four core areas: Uncountable trees, Ramsey theory on ordinals, Club-guessing principles, and Forcing Axioms. There is a rich bilateral interaction between any pair of the four different cores, but the proposed division will allow an efficient allocation of manpower, and will increase the chances of parallel success.
Summary
We propose to establish a research group that will unveil the combinatorial nature of the second uncountable cardinal. This includes its Ramsey-theoretic, order-theoretic, graph-theoretic and topological features. Among others, we will be directly addressing fundamental problems due to Erdos, Rado, Galvin, and Shelah.
While some of these problems are old and well-known, an unexpected series of breakthroughs from the last three years suggest that now is a promising point in time to carry out such a project. Indeed, through a short period, four previously unattainable problems concerning the second uncountable cardinal were successfully tackled: Aspero on a club-guessing problem of Shelah, Krueger on the club-isomorphism problem for Aronszajn trees, Neeman on the isomorphism problem for dense sets of reals, and the PI on the Souslin problem. Each of these results was obtained through the development of a completely new technical framework, and these frameworks could now pave the way for the solution of some major open questions.
A goal of the highest risk in this project is the discovery of a consistent (possibly, parameterized) forcing axiom that will (preferably, simultaneously) provide structure theorems for stationary sets, linearly ordered sets, trees, graphs, and partition relations, as well as the refutation of various forms of club-guessing principles, all at the level of the second uncountable cardinal. In comparison, at the level of the first uncountable cardinal, a forcing axiom due to Foreman, Magidor and Shelah achieves exactly that.
To approach our goals, the proposed project is divided into four core areas: Uncountable trees, Ramsey theory on ordinals, Club-guessing principles, and Forcing Axioms. There is a rich bilateral interaction between any pair of the four different cores, but the proposed division will allow an efficient allocation of manpower, and will increase the chances of parallel success.
Max ERC Funding
1 362 500 €
Duration
Start date: 2018-10-01, End date: 2023-09-30
Project acronym CLaQS
Project Correlations in Large Quantum Systems
Researcher (PI) Benjamin Schlein
Host Institution (HI) UNIVERSITAT ZURICH
Call Details Advanced Grant (AdG), PE1, ERC-2018-ADG
Summary This project is devoted to the mathematical analysis of important physical properties of many-body quantum systems. We will be interested in properties of the ground state and low-energy excitations but also of non-equilibrium dynamics. We are going to consider systems with different statistics and in different regimes. The questions we are going to address have a common aspect: correlations among particles play a crucial role. Our main goal consists in developing new tools that allow us to correctly describe many-body correlations and to understand their effects. The starting point of our proposal are ideas and techniques that have been introduced in a series of papers establishing the validity of Bogoliubov theory for Bose gases in the Gross-Pitaevskii regime, and in a recent preprint showing how (bosonic) Bogoliubov theory can also be used to study the correlation energy of Fermi gases. In this project, we plan to develop these techniques further and to apply them to new contexts. We believe they have the potential to approach some fundamental open problem in mathematical physics. Among our most ambitious objectives, we include the proof of the Lee-Huang-Yang formula for the energy of dilute Bose gases and of the corresponding Huang-Yang formula for dilute Fermi gases, as well as the derivation of the Gell-Mann--Brueckner expression for the correlation energy of a high density Fermi system. Furthermore, we propose to work on long-term projects (going beyond the duration of the grant) aiming at a rigorous justification of the quantum Boltzmann equation for fermions in the weak coupling limit and at a proof of Bose-Einstein condensation in the thermodynamic limit, two very challenging and important questions in the field.
Summary
This project is devoted to the mathematical analysis of important physical properties of many-body quantum systems. We will be interested in properties of the ground state and low-energy excitations but also of non-equilibrium dynamics. We are going to consider systems with different statistics and in different regimes. The questions we are going to address have a common aspect: correlations among particles play a crucial role. Our main goal consists in developing new tools that allow us to correctly describe many-body correlations and to understand their effects. The starting point of our proposal are ideas and techniques that have been introduced in a series of papers establishing the validity of Bogoliubov theory for Bose gases in the Gross-Pitaevskii regime, and in a recent preprint showing how (bosonic) Bogoliubov theory can also be used to study the correlation energy of Fermi gases. In this project, we plan to develop these techniques further and to apply them to new contexts. We believe they have the potential to approach some fundamental open problem in mathematical physics. Among our most ambitious objectives, we include the proof of the Lee-Huang-Yang formula for the energy of dilute Bose gases and of the corresponding Huang-Yang formula for dilute Fermi gases, as well as the derivation of the Gell-Mann--Brueckner expression for the correlation energy of a high density Fermi system. Furthermore, we propose to work on long-term projects (going beyond the duration of the grant) aiming at a rigorous justification of the quantum Boltzmann equation for fermions in the weak coupling limit and at a proof of Bose-Einstein condensation in the thermodynamic limit, two very challenging and important questions in the field.
Max ERC Funding
1 876 050 €
Duration
Start date: 2019-09-01, End date: 2024-08-31
Project acronym CURVATURE
Project Optimal transport techniques in the geometric analysis of spaces with curvature bounds
Researcher (PI) Andrea MONDINO
Host Institution (HI) THE UNIVERSITY OF WARWICK
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary The unifying goal of the CURVATURE project is to develop new strategies and tools in order to attack fundamental questions in the theory of smooth and non-smooth spaces satisfying (mainly Ricci or sectional) curvature restrictions/bounds.
The program involves analysis and geometry, with strong connections to probability and mathematical physics. The problems will be attacked by an innovative merging of geometric analysis and optimal transport techniques that already enabled the PI and collaborators to solve important open questions in the field.
The project is composed of three inter-connected themes:
Theme I investigates the structure of non smooth spaces with Ricci curvature bounded below and their link with
Alexandrov geometry. The goal of this theme is two-fold: on the one hand get a refined structural picture of
non-smooth spaces with Ricci curvature lower bounds, on the other hand apply the new methods to make progress in some long-standing open problems in Alexandrov geometry.
Theme II aims to achieve a unified treatment of geometric and functional inequalities for both smooth and
non-smooth, finite and infinite dimensional spaces satisfying Ricci curvature lower bounds. The approach
will be used also to establish new quantitative versions of classical geometric/functional inequalities for smooth Riemannian manifolds and to make progress in long standing open problems for both Riemannian and sub-Riemannian manifolds.
Theme III will investigate optimal transport in a Lorentzian setting, where the Ricci curvature plays a key
role in Einstein's equations of general relativity.
The three themes together will yield a unique unifying insight of smooth and non-smooth structures with curvature bounds.
Summary
The unifying goal of the CURVATURE project is to develop new strategies and tools in order to attack fundamental questions in the theory of smooth and non-smooth spaces satisfying (mainly Ricci or sectional) curvature restrictions/bounds.
The program involves analysis and geometry, with strong connections to probability and mathematical physics. The problems will be attacked by an innovative merging of geometric analysis and optimal transport techniques that already enabled the PI and collaborators to solve important open questions in the field.
The project is composed of three inter-connected themes:
Theme I investigates the structure of non smooth spaces with Ricci curvature bounded below and their link with
Alexandrov geometry. The goal of this theme is two-fold: on the one hand get a refined structural picture of
non-smooth spaces with Ricci curvature lower bounds, on the other hand apply the new methods to make progress in some long-standing open problems in Alexandrov geometry.
Theme II aims to achieve a unified treatment of geometric and functional inequalities for both smooth and
non-smooth, finite and infinite dimensional spaces satisfying Ricci curvature lower bounds. The approach
will be used also to establish new quantitative versions of classical geometric/functional inequalities for smooth Riemannian manifolds and to make progress in long standing open problems for both Riemannian and sub-Riemannian manifolds.
Theme III will investigate optimal transport in a Lorentzian setting, where the Ricci curvature plays a key
role in Einstein's equations of general relativity.
The three themes together will yield a unique unifying insight of smooth and non-smooth structures with curvature bounds.
Max ERC Funding
1 256 221 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym EffectiveTG
Project Effective Methods in Tame Geometry and Applications in Arithmetic and Dynamics
Researcher (PI) Gal BINYAMINI
Host Institution (HI) WEIZMANN INSTITUTE OF SCIENCE
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary Tame geometry studies structures in which every definable set has a
finite geometric complexity. The study of tame geometry spans several
interrelated mathematical fields, including semialgebraic,
subanalytic, and o-minimal geometry. The past decade has seen the
emergence of a spectacular link between tame geometry and arithmetic
following the discovery of the fundamental Pila-Wilkie counting
theorem and its applications in unlikely diophantine
intersections. The P-W theorem itself relies crucially on the
Yomdin-Gromov theorem, a classical result of tame geometry with
fundamental applications in smooth dynamics.
It is natural to ask whether the complexity of a tame set can be
estimated effectively in terms of the defining formulas. While a large
body of work is devoted to answering such questions in the
semialgebraic case, surprisingly little is known concerning more
general tame structures - specifically those needed in recent
applications to arithmetic. The nature of the link between tame
geometry and arithmetic is such that any progress toward effectivizing
the theory of tame structures will likely lead to effective results
in the domain of unlikely intersections. Similarly, a more effective
version of the Yomdin-Gromov theorem is known to imply important
consequences in smooth dynamics.
The proposed research will approach effectivity in tame geometry from
a fundamentally new direction, bringing to bear methods from the
theory of differential equations which have until recently never been
used in this context. Toward this end, our key goals will be to gain
insight into the differential algebraic and complex analytic structure
of tame sets; and to apply this insight in combination with results
from the theory of differential equations to effectivize key results
in tame geometry and its applications to arithmetic and dynamics. I
believe that my preliminary work in this direction amply demonstrates
the feasibility and potential of this approach.
Summary
Tame geometry studies structures in which every definable set has a
finite geometric complexity. The study of tame geometry spans several
interrelated mathematical fields, including semialgebraic,
subanalytic, and o-minimal geometry. The past decade has seen the
emergence of a spectacular link between tame geometry and arithmetic
following the discovery of the fundamental Pila-Wilkie counting
theorem and its applications in unlikely diophantine
intersections. The P-W theorem itself relies crucially on the
Yomdin-Gromov theorem, a classical result of tame geometry with
fundamental applications in smooth dynamics.
It is natural to ask whether the complexity of a tame set can be
estimated effectively in terms of the defining formulas. While a large
body of work is devoted to answering such questions in the
semialgebraic case, surprisingly little is known concerning more
general tame structures - specifically those needed in recent
applications to arithmetic. The nature of the link between tame
geometry and arithmetic is such that any progress toward effectivizing
the theory of tame structures will likely lead to effective results
in the domain of unlikely intersections. Similarly, a more effective
version of the Yomdin-Gromov theorem is known to imply important
consequences in smooth dynamics.
The proposed research will approach effectivity in tame geometry from
a fundamentally new direction, bringing to bear methods from the
theory of differential equations which have until recently never been
used in this context. Toward this end, our key goals will be to gain
insight into the differential algebraic and complex analytic structure
of tame sets; and to apply this insight in combination with results
from the theory of differential equations to effectivize key results
in tame geometry and its applications to arithmetic and dynamics. I
believe that my preliminary work in this direction amply demonstrates
the feasibility and potential of this approach.
Max ERC Funding
1 155 027 €
Duration
Start date: 2018-09-01, End date: 2023-08-31
Project acronym EFMA
Project Equidistribution, fractal measures and arithmetic
Researcher (PI) Peter Pal VARJU
Host Institution (HI) THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary The subject of this proposal lies at the crossroads of analysis, additive combinatorics, number theory and fractal geometry exploring equidistribution phenomena for random walks on groups and group actions and regularity properties of self-similar, self-affine and Furstenberg boundary measures and other kinds of stationary measures. Many of the problems I will study in this project are deeply linked with problems in number theory, such as bounds for the separation between algebraic numbers, Lehmer's conjecture and irreducibility of polynomials.
The central aim of the project is to gain insight into and eventually resolve problems in several main directions including the following. I will address the main challenges that remain in our understanding of the spectral gap of averaging operators on finite groups and Lie groups and I will study the applications of such estimates. I will build on the dramatic recent progress on a problem of Erdos from 1939 regarding Bernoulli convolutions. I will also investigate other families of fractal measures. I will examine the arithmetic properties (such as irreducibility and their Galois groups) of generic polynomials with bounded coefficients and in other related families of polynomials.
While these lines of research may seem unrelated, both the problems and the methods I propose to study them are deeply connected.
Summary
The subject of this proposal lies at the crossroads of analysis, additive combinatorics, number theory and fractal geometry exploring equidistribution phenomena for random walks on groups and group actions and regularity properties of self-similar, self-affine and Furstenberg boundary measures and other kinds of stationary measures. Many of the problems I will study in this project are deeply linked with problems in number theory, such as bounds for the separation between algebraic numbers, Lehmer's conjecture and irreducibility of polynomials.
The central aim of the project is to gain insight into and eventually resolve problems in several main directions including the following. I will address the main challenges that remain in our understanding of the spectral gap of averaging operators on finite groups and Lie groups and I will study the applications of such estimates. I will build on the dramatic recent progress on a problem of Erdos from 1939 regarding Bernoulli convolutions. I will also investigate other families of fractal measures. I will examine the arithmetic properties (such as irreducibility and their Galois groups) of generic polynomials with bounded coefficients and in other related families of polynomials.
While these lines of research may seem unrelated, both the problems and the methods I propose to study them are deeply connected.
Max ERC Funding
1 334 109 €
Duration
Start date: 2018-10-01, End date: 2023-09-30
Project acronym EllipticPDE
Project Regularity and singularities in elliptic PDE's: beyond monotonicity formulas
Researcher (PI) Xavier ROS-OTON
Host Institution (HI) UNIVERSITAT ZURICH
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary One of the oldest and most important questions in PDE theory is that of regularity. A classical example is Hilbert's XIXth problem (1900), solved by De Giorgi and Nash in 1956. During the second half of the XXth century, the regularity theory for elliptic and parabolic PDE's experienced a huge development, and many fundamental questions were answered by Caffarelli, Nirenberg, Krylov, Evans, Nadirashvili, Friedman, and many others. Still, there are problems of crucial importance that remain open.
The aim of this project is to go significantly beyond the state of the art in some of the most important open questions in this context. In particular, three key objectives of the project are the following. First, to introduce new techniques to obtain fine description of singularities in nonlinear elliptic PDE's. Aside from its intrinsic interest, a good regularity theory for singular points is likely to provide insightful applications in other contexts. A second aim of the project is to establish generic regularity results for free boundaries and other PDE problems. The development of methods which would allow one to prove generic regularity results may be viewed as one of the greatest challenges not only for free boundary problems, but for PDE problems in general. Finally, the third main objective is to achieve a complete regularity theory for nonlinear elliptic PDE's that does not rely on monotonicity formulas. These three objectives, while seemingly different, are in fact deeply interrelated.
Summary
One of the oldest and most important questions in PDE theory is that of regularity. A classical example is Hilbert's XIXth problem (1900), solved by De Giorgi and Nash in 1956. During the second half of the XXth century, the regularity theory for elliptic and parabolic PDE's experienced a huge development, and many fundamental questions were answered by Caffarelli, Nirenberg, Krylov, Evans, Nadirashvili, Friedman, and many others. Still, there are problems of crucial importance that remain open.
The aim of this project is to go significantly beyond the state of the art in some of the most important open questions in this context. In particular, three key objectives of the project are the following. First, to introduce new techniques to obtain fine description of singularities in nonlinear elliptic PDE's. Aside from its intrinsic interest, a good regularity theory for singular points is likely to provide insightful applications in other contexts. A second aim of the project is to establish generic regularity results for free boundaries and other PDE problems. The development of methods which would allow one to prove generic regularity results may be viewed as one of the greatest challenges not only for free boundary problems, but for PDE problems in general. Finally, the third main objective is to achieve a complete regularity theory for nonlinear elliptic PDE's that does not rely on monotonicity formulas. These three objectives, while seemingly different, are in fact deeply interrelated.
Max ERC Funding
1 335 250 €
Duration
Start date: 2019-01-01, End date: 2023-12-31
Project acronym Emergence
Project Emergence of wild differentiable dynamical systems
Researcher (PI) pierre berger
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary Many physical or biological systems display time-dependent states which can be mathematically modelled by a differentiable dynamical system. The state of the system consists of a finite number of variables, and the short time evolution is given by a differentiable equation or the iteration of a differentiable map. The evolution of a state is called an orbit of the system. The theory of dynamical systems studies the long time evolution of the orbits.
For some systems, called chaotic, it is impossible to predict the state of an orbit after a long period of time. However, in some cases, one may predict the probability of an orbit to have a certain state. A paradigm is given by the Boltzmann ergodic hypothesis in thermodynamics: over long periods of time, the time spent by a typical orbit in some region of the phase space is proportional to the “measure” of this region. The concept of Ergodicity has been mathematically formalized by Birkhoff. Then it has been successfully applied (in particular) by the schools of Kolmogorov and Anosov in the USSR, and Smale in the USA to describe the statistical behaviours of typical orbits of many differentiable dynamical systems.
For some systems, called wild, infinitely many possible statistical behaviour coexist. Those are spread all over a huge space of different ergodic measures, as initially discovered by Newhouse in the 70's. Such systems are completely misunderstood. In 2016, contrarily to the general belief, it has been discovered that wild systems form a rather typical set of systems (in some categories).
This project proposes the first global, ergodic study of wild dynamics, by focusing on dynamics which are too complex to be well described by means of finitely many statistics, as recently quantified by the notion of Emergence. Paradigmatic examples will be investigated and shown to be typical in many senses and among many categories. They will be used to construct a theory on wild dynamics around the concept of Emergence.
Summary
Many physical or biological systems display time-dependent states which can be mathematically modelled by a differentiable dynamical system. The state of the system consists of a finite number of variables, and the short time evolution is given by a differentiable equation or the iteration of a differentiable map. The evolution of a state is called an orbit of the system. The theory of dynamical systems studies the long time evolution of the orbits.
For some systems, called chaotic, it is impossible to predict the state of an orbit after a long period of time. However, in some cases, one may predict the probability of an orbit to have a certain state. A paradigm is given by the Boltzmann ergodic hypothesis in thermodynamics: over long periods of time, the time spent by a typical orbit in some region of the phase space is proportional to the “measure” of this region. The concept of Ergodicity has been mathematically formalized by Birkhoff. Then it has been successfully applied (in particular) by the schools of Kolmogorov and Anosov in the USSR, and Smale in the USA to describe the statistical behaviours of typical orbits of many differentiable dynamical systems.
For some systems, called wild, infinitely many possible statistical behaviour coexist. Those are spread all over a huge space of different ergodic measures, as initially discovered by Newhouse in the 70's. Such systems are completely misunderstood. In 2016, contrarily to the general belief, it has been discovered that wild systems form a rather typical set of systems (in some categories).
This project proposes the first global, ergodic study of wild dynamics, by focusing on dynamics which are too complex to be well described by means of finitely many statistics, as recently quantified by the notion of Emergence. Paradigmatic examples will be investigated and shown to be typical in many senses and among many categories. They will be used to construct a theory on wild dynamics around the concept of Emergence.
Max ERC Funding
1 070 343 €
Duration
Start date: 2019-09-01, End date: 2024-08-31
Project acronym FHiCuNCAG
Project Foundations for Higher and Curved Noncommutative Algebraic Geometry
Researcher (PI) Wendy Joy Lowen
Host Institution (HI) UNIVERSITEIT ANTWERPEN
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary With this research programme, inspired by open problems within noncommutative algebraic geometry (NCAG) as well as by actual developments in algebraic topology, it is our aim to lay out new foundations for NCAG. On the one hand, the categorical approach to geometry put forth in NCAG has seen a wide range of applications both in mathematics and in theoretical physics. On the other hand, algebraic topology has received a vast impetus from the development of higher topos theory by Lurie and others. The current project is aimed at cross-fertilisation between the two subjects, in particular through the development of “higher linear topos theory”. We will approach the higher structure on Hochschild type complexes from two angles. Firstly, focusing on intrinsic incarnations of spaces as large categories, we will use the tensor products developed jointly with Ramos González and Shoikhet to obtain a “large version” of the Deligne conjecture. Secondly, focusing on concrete representations, we will develop new operadic techniques in order to endow complexes like the Gerstenhaber-Schack complex for prestacks (due to Dinh Van-Lowen) and the deformation complexes for monoidal categories and pasting diagrams (due to Shrestha and Yetter) with new combinatorial structure. In another direction, we will move from Hochschild cohomology of abelian categories (in the sense of Lowen-Van den Bergh) to Mac Lane cohomology for exact categories (in the sense of Kaledin-Lowen), extending the scope of NCAG to “non-linear deformations”. One of the mysteries in algebraic deformation theory is the curvature problem: in the process of deformation we are brought to the boundaries of NCAG territory through the introduction of a curvature component which disables the standard approaches to cohomology. Eventually, it is our goal to set up a new framework for NCAG which incorporates curved objects, drawing inspiration from the realm of higher categories.
Summary
With this research programme, inspired by open problems within noncommutative algebraic geometry (NCAG) as well as by actual developments in algebraic topology, it is our aim to lay out new foundations for NCAG. On the one hand, the categorical approach to geometry put forth in NCAG has seen a wide range of applications both in mathematics and in theoretical physics. On the other hand, algebraic topology has received a vast impetus from the development of higher topos theory by Lurie and others. The current project is aimed at cross-fertilisation between the two subjects, in particular through the development of “higher linear topos theory”. We will approach the higher structure on Hochschild type complexes from two angles. Firstly, focusing on intrinsic incarnations of spaces as large categories, we will use the tensor products developed jointly with Ramos González and Shoikhet to obtain a “large version” of the Deligne conjecture. Secondly, focusing on concrete representations, we will develop new operadic techniques in order to endow complexes like the Gerstenhaber-Schack complex for prestacks (due to Dinh Van-Lowen) and the deformation complexes for monoidal categories and pasting diagrams (due to Shrestha and Yetter) with new combinatorial structure. In another direction, we will move from Hochschild cohomology of abelian categories (in the sense of Lowen-Van den Bergh) to Mac Lane cohomology for exact categories (in the sense of Kaledin-Lowen), extending the scope of NCAG to “non-linear deformations”. One of the mysteries in algebraic deformation theory is the curvature problem: in the process of deformation we are brought to the boundaries of NCAG territory through the introduction of a curvature component which disables the standard approaches to cohomology. Eventually, it is our goal to set up a new framework for NCAG which incorporates curved objects, drawing inspiration from the realm of higher categories.
Max ERC Funding
1 171 360 €
Duration
Start date: 2019-06-01, End date: 2024-05-31
Project acronym GTBB
Project General theory for Big Bayes
Researcher (PI) Judith Rousseau
Host Institution (HI) THE CHANCELLOR, MASTERS AND SCHOLARS OF THE UNIVERSITY OF OXFORD
Call Details Advanced Grant (AdG), PE1, ERC-2018-ADG
Summary In the modern era of complex and large data sets, there is stringent need for flexible, sound and scalable inferential methods to analyse them. Bayesian approaches have been increasingly used in statistics and machine learning and in all sorts of applications such as biostatistics, astrophysics, social science etc. Major advantages of Bayesian approaches are: their ability to model complex models in a hierarchical way, their coherency and ability to deliver not only point estimators but also measures of uncertainty from the posterior distribution which is a probability distribution on the parameter space at the core of all Bayesian inference. The increasing complexity of the data sets raise huge challenges for Bayesian approaches: theoretical and computational. The aim of this project is to develop a general theory for the analysis of Bayesian methods in complex and high (or infinite) dimensional models which will cover not only fine understanding of the posterior distributions but also an analysis of the output of the algorithms used to implement the approaches.
The main objectives of the project are (briefly):
1. Asymptotic analysis of the posterior distribution of complex high dimensional models
2. Interactions between the asymptotic theory of high dimensional posterior distributions and computational complexity.
We will also enrich these theoretical developments by 3 strongly related domains of applications, namely neuroscience, terrorism and crimes and ecology.
Summary
In the modern era of complex and large data sets, there is stringent need for flexible, sound and scalable inferential methods to analyse them. Bayesian approaches have been increasingly used in statistics and machine learning and in all sorts of applications such as biostatistics, astrophysics, social science etc. Major advantages of Bayesian approaches are: their ability to model complex models in a hierarchical way, their coherency and ability to deliver not only point estimators but also measures of uncertainty from the posterior distribution which is a probability distribution on the parameter space at the core of all Bayesian inference. The increasing complexity of the data sets raise huge challenges for Bayesian approaches: theoretical and computational. The aim of this project is to develop a general theory for the analysis of Bayesian methods in complex and high (or infinite) dimensional models which will cover not only fine understanding of the posterior distributions but also an analysis of the output of the algorithms used to implement the approaches.
The main objectives of the project are (briefly):
1. Asymptotic analysis of the posterior distribution of complex high dimensional models
2. Interactions between the asymptotic theory of high dimensional posterior distributions and computational complexity.
We will also enrich these theoretical developments by 3 strongly related domains of applications, namely neuroscience, terrorism and crimes and ecology.
Max ERC Funding
2 176 702 €
Duration
Start date: 2019-10-01, End date: 2024-09-30
Project acronym HiCoShiVa
Project Higher coherent coholomogy of Shimura varieties
Researcher (PI) Vincent Hubert Pilloni
Host Institution (HI) CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary One can attach certain complex analytic functions to algebraic varieties defined over the rational numbers, called Zeta functions. They are a vast generalization of Riemann’s zeta function. The Hasse-Weil conjecture predicts that these Zeta functions satisfy a functional equation and admit a meromorphic continuation to the whole complex plane. This follows from the conjectural Langlands program, which aims in particular at proving that Zeta functions of algebraic varieties are products of automorphic L-functions.
Automorphic forms belong to the representation theory of reductive groups but certain automorphic forms actually appear in the cohomology of locally symmetric spaces, and in particular the cohomology of automorphic vector bundles over Shimura varieties. This is a bridge towards arithmetic geometry.
There has been tremendous activity in this subject and the Hasse-Weil conjecture is known for proper smooth algebraic varieties over totally real number fields with regular Hodge numbers. This covers in particular the case of genus one curves. Nevertheless, lots of basic examples fail to have this regularity property : higher genus curves, Artin motives...
The project HiCoShiVa is focused on this irregular situation. On the Shimura Variety side we will have to deal with higher cohomology groups and torsion. The main innovation of the project is to construct p-adic variations of the coherent cohomology. We are able to consider higher coherent cohomology classes, while previous works in this area have been concerned with degree 0 cohomology.
The applications will be the construction of automorphic Galois representations, the modularity of irregular motives and new cases of the Hasse-Weil conjecture, and the construction of p-adic L-functions.
Summary
One can attach certain complex analytic functions to algebraic varieties defined over the rational numbers, called Zeta functions. They are a vast generalization of Riemann’s zeta function. The Hasse-Weil conjecture predicts that these Zeta functions satisfy a functional equation and admit a meromorphic continuation to the whole complex plane. This follows from the conjectural Langlands program, which aims in particular at proving that Zeta functions of algebraic varieties are products of automorphic L-functions.
Automorphic forms belong to the representation theory of reductive groups but certain automorphic forms actually appear in the cohomology of locally symmetric spaces, and in particular the cohomology of automorphic vector bundles over Shimura varieties. This is a bridge towards arithmetic geometry.
There has been tremendous activity in this subject and the Hasse-Weil conjecture is known for proper smooth algebraic varieties over totally real number fields with regular Hodge numbers. This covers in particular the case of genus one curves. Nevertheless, lots of basic examples fail to have this regularity property : higher genus curves, Artin motives...
The project HiCoShiVa is focused on this irregular situation. On the Shimura Variety side we will have to deal with higher cohomology groups and torsion. The main innovation of the project is to construct p-adic variations of the coherent cohomology. We are able to consider higher coherent cohomology classes, while previous works in this area have been concerned with degree 0 cohomology.
The applications will be the construction of automorphic Galois representations, the modularity of irregular motives and new cases of the Hasse-Weil conjecture, and the construction of p-adic L-functions.
Max ERC Funding
1 288 750 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym HomDyn
Project Homogenous dynamics, arithmetic and equidistribution
Researcher (PI) Elon Lindenstrauss
Host Institution (HI) THE HEBREW UNIVERSITY OF JERUSALEM
Call Details Advanced Grant (AdG), PE1, ERC-2018-ADG
Summary We consider the dynamics of actions on homogeneous spaces of algebraic groups,
and propose to tackle a wide range of problems in the area, including the central open problems.
One main focus in our proposal is the study of the intriguing and somewhat subtle rigidity properties of higher rank diagonal actions. We plan to develop new tools to study invariant measures for such actions, including the zero entropy case, and in particular Furstenberg's Conjecture about $\times 2,\times 3$-invariant measures on $\R / \Z$.
A second main focus is on obtaining quantitative and effective equidistribution and density results for unipotent flows, with emphasis on obtaining results with a polynomial error term.
One important ingredient in our study of both diagonalizable and unipotent actions is arithmetic combinatorics.
Interconnections between these subjects and arithmetic equidistribution properties, Diophantine approximations and automorphic forms will be pursued.
Summary
We consider the dynamics of actions on homogeneous spaces of algebraic groups,
and propose to tackle a wide range of problems in the area, including the central open problems.
One main focus in our proposal is the study of the intriguing and somewhat subtle rigidity properties of higher rank diagonal actions. We plan to develop new tools to study invariant measures for such actions, including the zero entropy case, and in particular Furstenberg's Conjecture about $\times 2,\times 3$-invariant measures on $\R / \Z$.
A second main focus is on obtaining quantitative and effective equidistribution and density results for unipotent flows, with emphasis on obtaining results with a polynomial error term.
One important ingredient in our study of both diagonalizable and unipotent actions is arithmetic combinatorics.
Interconnections between these subjects and arithmetic equidistribution properties, Diophantine approximations and automorphic forms will be pursued.
Max ERC Funding
2 090 625 €
Duration
Start date: 2019-06-01, End date: 2024-05-31
Project acronym ICOPT
Project Fundamental Problems at the Interface of Combinatorial Optimization with Integer Programming and Online Optimization
Researcher (PI) Rico Zenklusen
Host Institution (HI) EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary The goal of this proposal is to leverage and significantly extend techniques from the field of Combinatorial Optimization to address some fundamental open algorithmic questions in other, related areas, namely Integer Programming and Online Optimization. More precisely, we focus on the following three thrusts, which share many combinatorial features:
- Integer programming with bounded subdeterminants.
- Expressive power of mixed-integer linear formulations.
- The matroid secretary conjecture, a key online selection problem.
Recent significant progress, in which the PI played a central role, combined with new ideas, give hope to obtain breakthrough results in these fields. Many of the questions we consider are long-standing open problems in their respective area, and any progress is thus likely to be a significant contribution to Mathematical Optimization and Theoretical Computer Science. However, equally importantly, if progress can be achieved through the suggested methodologies, then this would create intriguing new links between different fields, which was a key driver in the selection of the above research thrusts.
Summary
The goal of this proposal is to leverage and significantly extend techniques from the field of Combinatorial Optimization to address some fundamental open algorithmic questions in other, related areas, namely Integer Programming and Online Optimization. More precisely, we focus on the following three thrusts, which share many combinatorial features:
- Integer programming with bounded subdeterminants.
- Expressive power of mixed-integer linear formulations.
- The matroid secretary conjecture, a key online selection problem.
Recent significant progress, in which the PI played a central role, combined with new ideas, give hope to obtain breakthrough results in these fields. Many of the questions we consider are long-standing open problems in their respective area, and any progress is thus likely to be a significant contribution to Mathematical Optimization and Theoretical Computer Science. However, equally importantly, if progress can be achieved through the suggested methodologies, then this would create intriguing new links between different fields, which was a key driver in the selection of the above research thrusts.
Max ERC Funding
1 443 422 €
Duration
Start date: 2019-11-01, End date: 2024-10-31
Project acronym IGOC
Project Interactions between Groups, Orbits, and Cartans
Researcher (PI) Xin Li
Host Institution (HI) QUEEN MARY UNIVERSITY OF LONDON
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary Recently, we discovered that the notion of Cartan subalgebras builds bridges between C*-algebras, topological dynamics, and geometric group theory. The goal of this research project is to develop our understanding of this concept in order to attack the following major open questions:
I. The UCT question
II. The Baum-Connes conjecture
III. The conjugacy problem for topological shifts
IV. Quasi-isometry rigidity for polycyclic groups
UCT stands for Universal Coefficient Theorem and is a crucial ingredient in classification. I want to make progress on the open question whether sufficiently regular C*-algebras satisfy the UCT, taking my joint work with Barlak as a starting point.
The Baum-Connes conjecture predicts a K-theory formula for group C*-algebras which has far-reaching applications in geometry and algebra as it implies open conjectures of Novikov and Kaplansky. My new approach to II will be based on Cartan subalgebras and the notion of independent resolutions due to Norling and myself.
Problem III asks for algorithms deciding which shifts are topologically conjugate. It has driven a lot of research in symbolic dynamics.
Conjecture IV asserts that every group quasi-isometric to a polycyclic group must already be virtually polycyclic. A solution would be a milestone in our understanding of solvable Lie groups.
To attack III and IV, I want to develop the new notion of continuous orbit equivalence which (as I recently showed) is closely related to Cartan subalgebras.
Problems I to IV address important challenges, so that any progress will result in a major breakthrough. On top of that, my project will initiate new interactions between several mathematical areas. It is exactly the right time to develop the proposed research programme as it takes up recent breakthroughs in classification of C*-algebras, orbit equivalence for Cantor minimal systems, and measured group theory, where measure-theoretic analogues of our key concepts have been highly successful.
Summary
Recently, we discovered that the notion of Cartan subalgebras builds bridges between C*-algebras, topological dynamics, and geometric group theory. The goal of this research project is to develop our understanding of this concept in order to attack the following major open questions:
I. The UCT question
II. The Baum-Connes conjecture
III. The conjugacy problem for topological shifts
IV. Quasi-isometry rigidity for polycyclic groups
UCT stands for Universal Coefficient Theorem and is a crucial ingredient in classification. I want to make progress on the open question whether sufficiently regular C*-algebras satisfy the UCT, taking my joint work with Barlak as a starting point.
The Baum-Connes conjecture predicts a K-theory formula for group C*-algebras which has far-reaching applications in geometry and algebra as it implies open conjectures of Novikov and Kaplansky. My new approach to II will be based on Cartan subalgebras and the notion of independent resolutions due to Norling and myself.
Problem III asks for algorithms deciding which shifts are topologically conjugate. It has driven a lot of research in symbolic dynamics.
Conjecture IV asserts that every group quasi-isometric to a polycyclic group must already be virtually polycyclic. A solution would be a milestone in our understanding of solvable Lie groups.
To attack III and IV, I want to develop the new notion of continuous orbit equivalence which (as I recently showed) is closely related to Cartan subalgebras.
Problems I to IV address important challenges, so that any progress will result in a major breakthrough. On top of that, my project will initiate new interactions between several mathematical areas. It is exactly the right time to develop the proposed research programme as it takes up recent breakthroughs in classification of C*-algebras, orbit equivalence for Cantor minimal systems, and measured group theory, where measure-theoretic analogues of our key concepts have been highly successful.
Max ERC Funding
1 296 966 €
Duration
Start date: 2019-09-01, End date: 2024-08-31
Project acronym KAPIBARA
Project Homotopy Theory of Algebraic Varieties and Wild Ramification
Researcher (PI) Piotr ACHINGER
Host Institution (HI) INSTYTUT MATEMATYCZNY POLSKIEJ AKADEMII NAUK
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary The aim of the proposed research is to study the homotopy theory of algebraic varieties and other algebraically defined geometric objects, especially over fields other than the complex numbers. A noticeable emphasis will be put on fundamental groups and on K(pi, 1) spaces, which serve as building blocks for more complicated objects. The most important source of both motivation and methodology is my recent discovery of the K(pi, 1) property of affine schemes in positive characteristic and its relation to wild ramification phenomena.
The central goal is the study of etale homotopy types in positive characteristic, where we hope to use the aforementioned discovery to yield new results beyond the affine case and a better understanding of the fundamental group of affine schemes. The latter goal is closely tied to Grothendieck's anabelian geometry program, which we would like to extend beyond its usual scope of hyperbolic curves.
There are two bridges going out of this central point. The first is the analogy between wild ramification and irregular singularities of algebraic integrable connections, which prompts us to translate our results to the latter setting, and to define a wild homotopy type whose fundamental group encodes the category of connections.
The second bridge is the theory of perfectoid spaces, allowing one to pass between characteristic p and p-adic geometry, which we plan to use to shed some new light on the homotopy theory of adic spaces. At the same time, we address the related question: when is the universal cover of a p-adic variety a perfectoid space? We expect a connection between this question and the Shafarevich conjecture and varieties with large fundamental group.
The last part of the project deals with varieties over the field of formal Laurent series over C, where we want to construct a Betti homotopy realization using logarithmic geometry. The need for such a construction is motivated by certain questions in mirror symmetry.
Summary
The aim of the proposed research is to study the homotopy theory of algebraic varieties and other algebraically defined geometric objects, especially over fields other than the complex numbers. A noticeable emphasis will be put on fundamental groups and on K(pi, 1) spaces, which serve as building blocks for more complicated objects. The most important source of both motivation and methodology is my recent discovery of the K(pi, 1) property of affine schemes in positive characteristic and its relation to wild ramification phenomena.
The central goal is the study of etale homotopy types in positive characteristic, where we hope to use the aforementioned discovery to yield new results beyond the affine case and a better understanding of the fundamental group of affine schemes. The latter goal is closely tied to Grothendieck's anabelian geometry program, which we would like to extend beyond its usual scope of hyperbolic curves.
There are two bridges going out of this central point. The first is the analogy between wild ramification and irregular singularities of algebraic integrable connections, which prompts us to translate our results to the latter setting, and to define a wild homotopy type whose fundamental group encodes the category of connections.
The second bridge is the theory of perfectoid spaces, allowing one to pass between characteristic p and p-adic geometry, which we plan to use to shed some new light on the homotopy theory of adic spaces. At the same time, we address the related question: when is the universal cover of a p-adic variety a perfectoid space? We expect a connection between this question and the Shafarevich conjecture and varieties with large fundamental group.
The last part of the project deals with varieties over the field of formal Laurent series over C, where we want to construct a Betti homotopy realization using logarithmic geometry. The need for such a construction is motivated by certain questions in mirror symmetry.
Max ERC Funding
1 007 500 €
Duration
Start date: 2019-06-01, End date: 2024-05-31
Project acronym LIMITS
Project Limits of Structures in Algebra and Combinatorics
Researcher (PI) Lukasz GRABOWSKI
Host Institution (HI) UNIVERSITY OF LANCASTER
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary The project is concerned with Borel and measurable combinatorics, sparse
graph limits, approximation of algebraic structures and applications to
metric geometry and measured group theory. Our research will result in
major advances in these areas, and will create new research directions in
combinatorics, analysis and commutative algebra.
The main research objectives are as follows.
1) Study equidecompositions of sets and solve the Borel version of the Ruziewicz problem.
2) Give a new characterisation of amenable groups in terms of measurable Lovasz Local Lemma.
3) Study rank approximations of infinite groups and commutative algebras.
Summary
The project is concerned with Borel and measurable combinatorics, sparse
graph limits, approximation of algebraic structures and applications to
metric geometry and measured group theory. Our research will result in
major advances in these areas, and will create new research directions in
combinatorics, analysis and commutative algebra.
The main research objectives are as follows.
1) Study equidecompositions of sets and solve the Borel version of the Ruziewicz problem.
2) Give a new characterisation of amenable groups in terms of measurable Lovasz Local Lemma.
3) Study rank approximations of infinite groups and commutative algebras.
Max ERC Funding
1 139 333 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym MaMBoQ
Project Macroscopic Behavior of Many-Body Quantum Systems
Researcher (PI) Marcello PORTA
Host Institution (HI) EBERHARD KARLS UNIVERSITAET TUEBINGEN
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary This project is devoted to the analysis of large quantum systems. It is divided in two parts: Part A focuses on the transport properties of interacting lattice models, while Part B concerns the derivation of effective evolution equations for many-body quantum systems. The common theme is the concept of emergent effective theory: simplified models capturing the macroscopic behavior of complex systems. Different systems might share the same effective theory, a phenomenon called universality. A central goal of mathematical physics is to validate these approximations, and to understand the emergence of universality from first principles.
Part A: Transport in interacting condensed matter systems. I will study charge and spin transport in 2d systems, such as graphene and topological insulators. These materials attracted enormous interest, because of their remarkable conduction properties. Neglecting many-body interactions, some of these properties can be explained mathematically. In real samples, however, electrons do interact. In order to deal with such complex systems, physicists often rely on uncontrolled expansions, numerical methods, or formal mappings in exactly solvable models. The goal is to rigorously understand the effect of many-body interactions, and to explain the emergence of universality.
Part B: Effective dynamics of interacting fermionic systems. I will work on the derivation of effective theories for interacting fermions, in suitable scaling regimes. In the last 18 years, there has been great progress on the rigorous validity of celebrated effective models, e.g. Hartree and Gross-Pitaevskii theory. A lot is known for interacting bosons, for the dynamics and for the equilibrium low energy properties. Much less is known for fermions. The goal is fill the gap by proving the validity of some well-known fermionic effective theories, such as Hartree-Fock and BCS theory in the mean-field scaling, and the quantum Boltzmann equation in the kinetic scaling.
Summary
This project is devoted to the analysis of large quantum systems. It is divided in two parts: Part A focuses on the transport properties of interacting lattice models, while Part B concerns the derivation of effective evolution equations for many-body quantum systems. The common theme is the concept of emergent effective theory: simplified models capturing the macroscopic behavior of complex systems. Different systems might share the same effective theory, a phenomenon called universality. A central goal of mathematical physics is to validate these approximations, and to understand the emergence of universality from first principles.
Part A: Transport in interacting condensed matter systems. I will study charge and spin transport in 2d systems, such as graphene and topological insulators. These materials attracted enormous interest, because of their remarkable conduction properties. Neglecting many-body interactions, some of these properties can be explained mathematically. In real samples, however, electrons do interact. In order to deal with such complex systems, physicists often rely on uncontrolled expansions, numerical methods, or formal mappings in exactly solvable models. The goal is to rigorously understand the effect of many-body interactions, and to explain the emergence of universality.
Part B: Effective dynamics of interacting fermionic systems. I will work on the derivation of effective theories for interacting fermions, in suitable scaling regimes. In the last 18 years, there has been great progress on the rigorous validity of celebrated effective models, e.g. Hartree and Gross-Pitaevskii theory. A lot is known for interacting bosons, for the dynamics and for the equilibrium low energy properties. Much less is known for fermions. The goal is fill the gap by proving the validity of some well-known fermionic effective theories, such as Hartree-Fock and BCS theory in the mean-field scaling, and the quantum Boltzmann equation in the kinetic scaling.
Max ERC Funding
982 625 €
Duration
Start date: 2019-02-01, End date: 2024-01-31
Project acronym NBEB-SSP
Project Nonparametric Bayes and empirical Bayes for species sampling problems: classical questions, new directions and related issues
Researcher (PI) Stefano FAVARO
Host Institution (HI) UNIVERSITA DEGLI STUDI DI TORINO
Call Details Consolidator Grant (CoG), PE1, ERC-2018-COG
Summary Consider a population of individuals belonging to different species with unknown proportions. Given an
initial (observable) random sample from the population, how do we estimate the number of species in the
population, or the probability of discovering a new species in one additional sample, or the number of
hitherto unseen species that would be observed in additional unobservable samples? These are archetypal
examples of a broad class of statistical problems referred to as species sampling problems (SSP), namely:
statistical problems in which the objects of inference are functionals involving the unknown species
proportions and/or the species frequency counts induced by observable and unobservable samples from the
population. SSPs first appeared in ecology, and their importance has grown considerably in the recent years
driven by challenging applications in a wide range of leading scientific disciplines, e.g., biosciences and
physical sciences, engineering sciences, machine learning, theoretical computer science and information
theory, etc.
The objective of this project is the introduction and a thorough investigation of new nonparametric Bayes
and empirical Bayes methods for SSPs. The proposed advances will include: i) addressing challenging
methodological open problems in classical SSPs under the nonparametric empirical Bayes framework, which
is arguably the most developed (currently most implemented by practitioners) framework do deal with
classical SSPs; fully exploiting and developing the potential of tools from mathematical analysis,
combinatorial probability and Bayesian nonparametric statistics to set forth a coherent modern approach to
classical SSPs, and then investigating the interplay between this approach and its empirical counterpart;
extending the scope of the above studies to more challenging SSPs, and classes of generalized SSPs, that
have emerged recently in the fields of biosciences and physical sciences, machine learning and information
theory.
Summary
Consider a population of individuals belonging to different species with unknown proportions. Given an
initial (observable) random sample from the population, how do we estimate the number of species in the
population, or the probability of discovering a new species in one additional sample, or the number of
hitherto unseen species that would be observed in additional unobservable samples? These are archetypal
examples of a broad class of statistical problems referred to as species sampling problems (SSP), namely:
statistical problems in which the objects of inference are functionals involving the unknown species
proportions and/or the species frequency counts induced by observable and unobservable samples from the
population. SSPs first appeared in ecology, and their importance has grown considerably in the recent years
driven by challenging applications in a wide range of leading scientific disciplines, e.g., biosciences and
physical sciences, engineering sciences, machine learning, theoretical computer science and information
theory, etc.
The objective of this project is the introduction and a thorough investigation of new nonparametric Bayes
and empirical Bayes methods for SSPs. The proposed advances will include: i) addressing challenging
methodological open problems in classical SSPs under the nonparametric empirical Bayes framework, which
is arguably the most developed (currently most implemented by practitioners) framework do deal with
classical SSPs; fully exploiting and developing the potential of tools from mathematical analysis,
combinatorial probability and Bayesian nonparametric statistics to set forth a coherent modern approach to
classical SSPs, and then investigating the interplay between this approach and its empirical counterpart;
extending the scope of the above studies to more challenging SSPs, and classes of generalized SSPs, that
have emerged recently in the fields of biosciences and physical sciences, machine learning and information
theory.
Max ERC Funding
982 930 €
Duration
Start date: 2019-03-01, End date: 2024-02-29
Project acronym PariTorMod
Project P-adic Arithmetic Geometry, Torsion Classes, and Modularity
Researcher (PI) Ana CARAIANI
Host Institution (HI) IMPERIAL COLLEGE OF SCIENCE TECHNOLOGY AND MEDICINE
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary The overall theme of the proposal is the interplay between p-adic arithmetic geometry and the Langlands correspondence for number fields. At the heart of the Langlands program lies reciprocity, which connects Galois representations to automorphic forms. Recently, new developments in p-adic arithmetic geometry, such as the theory of perfectoid spaces, have had a transformative effect on the field. This proposal would establish a research group that will develop and exploit novel techniques, that will allow us to move significantly beyond the state of art. I intend to make fundamental progress on three major interlinked problems.
Torsion in the cohomology of Shimura varieties: in joint work with Scholze, I proved a strong vanishing result for torsion in the cohomology of compact unitary Shimura varieties. In work in progress, we have extended this to many non-compact cases. To obtain a complete picture, I propose to develop new techniques using point-counting and the trace formula and combine them with ingredients from arithmetic geometry.
Local-global compatibility is essential for establishing new instances of Langlands reciprocity. I will use the results on Shimura varieties described above to prove local-global compatibility for torsion in the cohomology of locally symmetric spaces for general linear groups over CM fields. This is one of the fundamental questions in the field. Solving it will require progress on a diverse set of problems in representation theory and integral p-adic Hodge theory.
The Fontaine–Mazur conjecture is the most general reciprocity conjecture. Very little is known outside the case of two-dimensional representations of the absolute Galois group of the rational numbers, which relies crucially on a connection to p-adic local Langlands. I will attack the Fontaine–Mazur conjecture for imaginary quadratic fields. Some crucial inputs will come from the first two projects above.
Summary
The overall theme of the proposal is the interplay between p-adic arithmetic geometry and the Langlands correspondence for number fields. At the heart of the Langlands program lies reciprocity, which connects Galois representations to automorphic forms. Recently, new developments in p-adic arithmetic geometry, such as the theory of perfectoid spaces, have had a transformative effect on the field. This proposal would establish a research group that will develop and exploit novel techniques, that will allow us to move significantly beyond the state of art. I intend to make fundamental progress on three major interlinked problems.
Torsion in the cohomology of Shimura varieties: in joint work with Scholze, I proved a strong vanishing result for torsion in the cohomology of compact unitary Shimura varieties. In work in progress, we have extended this to many non-compact cases. To obtain a complete picture, I propose to develop new techniques using point-counting and the trace formula and combine them with ingredients from arithmetic geometry.
Local-global compatibility is essential for establishing new instances of Langlands reciprocity. I will use the results on Shimura varieties described above to prove local-global compatibility for torsion in the cohomology of locally symmetric spaces for general linear groups over CM fields. This is one of the fundamental questions in the field. Solving it will require progress on a diverse set of problems in representation theory and integral p-adic Hodge theory.
The Fontaine–Mazur conjecture is the most general reciprocity conjecture. Very little is known outside the case of two-dimensional representations of the absolute Galois group of the rational numbers, which relies crucially on a connection to p-adic local Langlands. I will attack the Fontaine–Mazur conjecture for imaginary quadratic fields. Some crucial inputs will come from the first two projects above.
Max ERC Funding
1 469 805 €
Duration
Start date: 2019-01-01, End date: 2023-12-31
Project acronym PATHWISE
Project Pathwise methods and stochastic calculus in the path towards understanding high-dimensional phenomena
Researcher (PI) Ronen ELDAN
Host Institution (HI) WEIZMANN INSTITUTE OF SCIENCE
Call Details Starting Grant (StG), PE1, ERC-2018-STG
Summary Concepts from the theory of high-dimensional phenomena play a role in several areas of mathematics, statistics and computer science. Many results in this theory rely on tools and ideas originating in adjacent fields, such as transportation of measure, semigroup theory and potential theory. In recent years, a new symbiosis with the theory of stochastic calculus is emerging.
In a few recent works, by developing a novel approach of pathwise analysis, my coauthors and I managed to make progress in several central high-dimensional problems. This emerging method relies on the introduction of a stochastic process which allows one to associate quantities and properties related to the high-dimensional object of interest to corresponding notions in stochastic calculus, thus making the former tractable through the analysis of the latter.
We propose to extend this approach towards several long-standing open problems in high dimensional probability and geometry. First, we aim to explore the role of convexity in concentration inequalities, focusing on three central conjectures regarding the distribution of mass on high dimensional convex bodies: the Kannan-Lov'asz-Simonovits (KLS) conjecture, the variance conjecture and the hyperplane conjecture as well as emerging connections with quantitative central limit theorems, entropic jumps and stability bounds for the Brunn-Minkowski inequality. Second, we are interested in dimension-free inequalities in Gaussian space and on the Boolean hypercube: isoperimetric and noise-stability inequalities and robustness thereof, transportation-entropy and concentration inequalities, regularization properties of the heat-kernel and L_1 versions of hypercontractivity. Finally, we are interested in developing new methods for the analysis of Gibbs distributions with a mean-field behavior, related to the new theory of nonlinear large deviations, and towards questions regarding interacting particle systems and the analysis of large networks.
Summary
Concepts from the theory of high-dimensional phenomena play a role in several areas of mathematics, statistics and computer science. Many results in this theory rely on tools and ideas originating in adjacent fields, such as transportation of measure, semigroup theory and potential theory. In recent years, a new symbiosis with the theory of stochastic calculus is emerging.
In a few recent works, by developing a novel approach of pathwise analysis, my coauthors and I managed to make progress in several central high-dimensional problems. This emerging method relies on the introduction of a stochastic process which allows one to associate quantities and properties related to the high-dimensional object of interest to corresponding notions in stochastic calculus, thus making the former tractable through the analysis of the latter.
We propose to extend this approach towards several long-standing open problems in high dimensional probability and geometry. First, we aim to explore the role of convexity in concentration inequalities, focusing on three central conjectures regarding the distribution of mass on high dimensional convex bodies: the Kannan-Lov'asz-Simonovits (KLS) conjecture, the variance conjecture and the hyperplane conjecture as well as emerging connections with quantitative central limit theorems, entropic jumps and stability bounds for the Brunn-Minkowski inequality. Second, we are interested in dimension-free inequalities in Gaussian space and on the Boolean hypercube: isoperimetric and noise-stability inequalities and robustness thereof, transportation-entropy and concentration inequalities, regularization properties of the heat-kernel and L_1 versions of hypercontractivity. Finally, we are interested in developing new methods for the analysis of Gibbs distributions with a mean-field behavior, related to the new theory of nonlinear large deviations, and towards questions regarding interacting particle systems and the analysis of large networks.
Max ERC Funding
1 308 188 €
Duration
Start date: 2019-01-01, End date: 2023-12-31
