The informal seminar is open to all visitors at IHES and researchers in the Paris area. We aim at keeping the informality, which implies, many (friendly) interruptions, many (smart and stupid) questions, spontaneous (blackboard only, sometimes unfinished) talks, and a welcoming atmosphere.

## Organizers:

Thierry Bodineau, Pieter Lammers, Yilin Wang

If you want to be added to the mailing list, please write to Yilin (yilin@ihes.fr)

If you want to be added to the mailing list, please write to Yilin (yilin@ihes.fr)

## IHES (Amphi Motchane or Centre de conference)

## Up-coming sessions

**Thursday, Feb. 9**

**11: 00 - 13: 00**

(Centre de conférences Marilyn et James Simons)

**Barbara Dembin**(ETHZ)

Upper tail large deviations for chemical distance in supercritical percolation

We consider supercritical bond percolation on Z^d and study the chemical distance, i.e., the graph distance on the infinite cluster. It is well-known that there exists a deterministic constant μ(x) such that the chemical distance D(0,nx) between two connected points 0 and nx grows like nμ(x). We prove the existence of the rate function for the upper tail large deviation event {D(0,nx)>nμ(x)(1+ϵ),0< - >nx} for d>=3. Joint work with Shuta Nakajima.

**Pieter Lammers**(IHES)

A mass identity for the 2D XY model

The 2D XY model has attracted attention of physicists and mathematicians for several decades. One way to understand this model is through its dual height function. Recent developments make it possible to show that the phase transitions of the two models coincide. At the core of the proof is a new perspective on the Symanzik/Brydges–Fröhlich–Spencer random walk. The talk is based on arXiv:2301.06905 (Bijecting the BKT transition) and arXiv:2211.14365 (A dichotomy theory for height functions).

**Thursday Feb. 16**

**11: 00 - 13: 00**

(Centre de conférences Marilyn et James Simons)

**Scott Armstrong**(NYU) Lecture (2/3)

Quantitative homogenization for probabilists

The goal of this informal lecture series is to explain the analysis/PDE point of view of some problems which arise in statistical physics and probability. I will try to argue that the language of elliptic/parabolic homogenization brings a new perspective to a wide range of problems, and that the quantitative "coarse-graining" methods are surprisingly useful and adaptable. We will try to cover the first part of the recent monograph co-written with Tuomo Kuusi (available here: https://arxiv.org/abs/2210.06488), and then proceed based on the interests of the audience.

**Thursday Feb. 23**

**11: 00 - 13: 00**

(Centre de conférences Marilyn et James Simons)

**Scott Armstrong**(NYU) Lecture (3/3)

Quantitative homogenization for probabilists

The goal of this informal lecture series is to explain the analysis/PDE point of view of some problems which arise in statistical physics and probability. I will try to argue that the language of elliptic/parabolic homogenization brings a new perspective to a wide range of problems, and that the quantitative "coarse-graining" methods are surprisingly useful and adaptable. We will try to cover the first part of the recent monograph co-written with Tuomo Kuusi (available here: https://arxiv.org/abs/2210.06488), and then proceed based on the interests of the audience.

**Friday Mar. 10**

**14:00 - 16:00**

(Amphi Motchane)

**Amaury Freslon**(Paris-Saclay)

**Angeliki Menegaki**(IHES)

**Friday Mar. 24**

**14:00 - 16:00**

(Amphi Motchane)

**Trishen Gunaratnam**(University of Geneva)

**Romain Panis**(University of Geneva)

**Friday Apr. 14**

**14:00 - 16:00**

(Amphi Motchane)

**Gérard Ben Arous**(NYU)

**Friday Apr. 21**

**14:00 - 16:00**

(Amphi Motchane)

**Anton Zorich**(Paris Diderot)

Friday Apr. 28

Friday May 5

Friday May 12

Friday Apr. 28

Friday May 5

Friday May 12

## Past sessions 2023

**Thursday, Feb. 2**(Centre de conférences Marilyn et James Simons)

**Scott Armstrong**(NYU) Lecture (1/3)

Quantitative homogenization for probabilists

The goal of this informal lecture series is to explain the analysis/PDE point of view of some problems which arise in statistical physics and probability. I will try to argue that the language of elliptic/parabolic homogenization brings a new perspective to a wide range of problems, and that the quantitative "coarse-graining" methods are surprisingly useful and adaptable. We will try to cover the first part of the recent monograph co-written with Tuomo Kuusi (available here: https://arxiv.org/abs/2210.06488), and then proceed based on the interests of the audience.

**(Centre de conférences Marilyn et James Simons)**

Thursday, Jan. 19, 2023

Thursday, Jan. 19, 2023

**Dmitry Chelkak**(U. Michigan)

Convergence of double-dimers to CLE(4) via isomonodromic tau-functions

The main goal of this talk is to discuss a series of works (Kenyon’11, Dubédat’14, Basok-Ch.’18, Bai-Wan’21) on the convergence of double-dimer loop ensembles in Temperleyan domains to the nested CLE(4). Contrary to the convergence results available for several other lattice models in 2D (LERW/UST, critical Ising and percolation), this approach does not rely upon martingale observables for single interfaces and uses a probabilistic interpretation of a certain SL(2)-isomonodromic tau-function instead.

The plan is to start with a crash introduction on what is known/predicted for the scaling limits of loop O(N) models in 2D – even though this is not directly related to the main subject of the talk – so as to keep a bigger picture in mind and to have more room for informal questions/discussions.

**Jan. 5, 2023 Amphi Motchane 11-13**

Junchen Rong(IHES)

Junchen Rong

Hand-waving introduction to two-dimensional conformal field theory.

I will try to explain the representation theory of the Virasoro algebra and its application to various statistical physics models such as the Ising model and the free compact boson (Gaussian free field) theory. If time permits, I will also discuss the space of c=1 conformal field theories.

**Jiaming Xia**(IHES)

We consider the random field Ising model on Z^2 with external field i.i.d. N(0,\epsilon). I will present that under nonnegative temperatures, the effect of boundary conditions at distance N away on the magnetization in a finite box decays exponentially. I will first talk about the perturbative analysis, which is a crucial tool used in the proof, and then about the similarities in the proofs of the zero temperature case and the positive temperature case. This talk is based on the joint work with Jian Ding.

## Past sessions 2022

**Dec. 5**

CharlotteDietze (LMU Munich)

Charlotte

will talk about Dispersive Estimates for Nonlinear Schrödinger Equations with External Potentials

"We consider the long time dynamics of nonlinear Schrödinger equations with an external potential. More precisely, we look at Hartree type equations in three or higher dimensions with small initial data. We prove an optimal decay estimate, which is comparable to the decay of free solutions. Our proof relies on good control on a high Sobolev norm of the solution to estimate the terms in Duhamel's formula."

**Hong-Bin Chen**(IHES)

will talk about small noise perturbation of an ODE (resulting in an SDE with vanishing diffusion term). In particular, about the exit distribution on the boundary of a domain in which the dynamics is released.

...And a few other sessions before the webpage existed...

@ IHES, Bures-sur-Yvette, France