# Seminars (SRQW01)

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Event When Speaker Title Presentation Material
SRQW01 3rd September 2018
10:00 to 11:00
Antti Kupiainen Introduction to the Renormalisation Group - 1
Lecture notes for the course are at:
https://courses.helsinki.fi/sites/default/files/course-material/4594153/MathPhys2018final.pdf
We discuss parts of sections 4,6,7,8,9 which are self contained
SRQW01 3rd September 2018
11:30 to 12:30
Antti Kupiainen Introduction to the Renormalisation Group - 2
SRQW01 3rd September 2018
13:30 to 14:30
Martin Hairer Stochastic quantisation of Yang-Mills
Co-authors: Ajay Chandra (Imperial College London), Hao Shen (Columbia University)
SRQW01 3rd September 2018
14:30 to 15:30
Lorenzo Zambotti Renormalisation in regularity structures - part 1
This should be a mini-course on the algebraic side of the theory of regularity structures.
SRQW01 3rd September 2018
16:00 to 17:00
Felix Otto Regularity structures: Reconstruction and Integration - part 1
This minicourse is coordinated with the one of Lorenzo Zambotti. The joint goal is to treat the dynamical phi-4-3 model. This minicourse will provide the basic notions in regularity structures and discuss reconstruction and integration. It will mostly follow Martin Hairer's 2015 notes "Regularity structures and the dynamical phi-4-3 model''.
SRQW01 4th September 2018
09:00 to 10:00
Felix Otto Regularity structures: Reconstruction and Integration - part 2
This minicourse is coordinated with the one of Lorenzo Zambotti. The joint goal is to treat the dynamical phi-4-3 model. This minicourse will provide the basic notions in regularity structures and discuss reconstruction and integration. It will mostly follow Martin Hairer's 2015 notes "Regularity structures and the dynamical phi-4-3 model''.
SRQW01 4th September 2018
10:00 to 11:00
Lorenzo Zambotti Renormalisation in regularity structures - part 2
This should be a mini-course on the algebraic side of the theory of regularity structures.
SRQW01 4th September 2018
11:30 to 12:30
Antti Kupiainen Introduction to the Renormalisation Group - 3
SRQW01 4th September 2018
13:30 to 14:30
Vieri Mastropietro Universality in solid state physics and Constructive Renormalization Group
I will review some universality results in graphene and Hall insulators obtained by Renormalization Group methods.
SRQW01 4th September 2018
14:30 to 15:30
Antti Kupiainen Introduction to the Renormalisation Group - 4
SRQW01 4th September 2018
16:00 to 17:00
Slava Rychkov CFT and the bootstrap
SRQW01 5th September 2018
09:00 to 10:00
Felix Otto Regularity structures: Reconstruction and Integration - part 3
This minicourse is coordinated with the one of Lorenzo Zambotti. The joint goal is to treat the dynamical phi-4-3 model. This minicourse will provide the basic notions in regularity structures and discuss reconstruction and integration. It will mostly follow Martin Hairer's 2015 notes "Regularity structures and the dynamical phi-4-3 model''.
SRQW01 5th September 2018
10:00 to 11:00
Lorenzo Zambotti Renormalisation in regularity structures - part 3
This should be a mini-course on the algebraic side of the theory of regularity structures.
SRQW01 5th September 2018
11:30 to 12:30
Horst Knoerrer Symmetry breaking in a gas of bosons - an approach using constructive field theory
T.Balaban, J.Feldman, E.Trubowitz and the speaker have the long term goal to rigorously demonstrate symmetry breaking in a gas of weakly interaction bosons hopping on a three-dimensional lattice. Technically, to show that the correlation functions decay at a nonintegrable rate when the chemical potential is sufficiently positive, the nonintegrability reflecting the presence of a long range Goldstone boson mediating the inteaction between quasiparticles in the superfluid condensate.

In addition to a report on the status of this program, I will try to describe in more detail the method of block spin transformations that we use to define and control a renormalization group flow.
SRQW01 6th September 2018
09:00 to 10:00
Gordon Slade Renormalisation group and critical phenomena - 1
The understanding of critical phenomena via the renormalisation group approach is one of the great achievements of theoretical physics during the last half of the previous century. This series of lectures will begin with an introduction to the critical behaviour of the phi^4 lattice spin system and its supersymmetric counterpart (the weakly self-avoiding walk). The lectures will mainly be occupied with an introduction to a rigorous renormalisation group method that has been developed and used to compute critical exponents for these models in the upper critical dimension d=4, and also below the critical dimension for long-range models. The lectures are based on collaborations with David Brydges and Roland Bauerschmidt.
SRQW01 6th September 2018
10:00 to 11:00
Nicolas Perkowski Infinite-dimensional paracontrolled distributions: the Burgers generator
Regularity structures, paracontrolled distributions and all that provide pathwise, deterministic tools to solve and study singular stochastic PDEs over finite-dimensional spaces. From a probabilistic point of view we would also like to understand the associated Kolmogorov backward equations, which can be interpreted as infinite-dimensional singular SPDEs. I will discuss on the example of the conservative stochastic Burgers equation how to construct a space of (para-) paracontrolled distributions in which the backward equation is well posed. As an application we obtain a martingale formulation and an alternative proof for the well-posedness of "energy solutions", without using the Cole-Hopf transform. The approach extends to some other singular SPDEs with Gaussian invariant measures and quadratic nonlinearities. This is joint work with Massimiliano Gubinelli.
SRQW01 6th September 2018
11:30 to 12:30
Gordon Slade Renormalisation group and critical phenomena - 2
The understanding of critical phenomena via the renormalisation group approach is one of the great achievements of theoretical physics during the last half of the previous century. This series of lectures will begin with an introduction to the critical behaviour of the phi^4 lattice spin system and its supersymmetric counterpart (the weakly self-avoiding walk). The lectures will mainly be occupied with an introduction to a rigorous renormalisation group method that has been developed and used to compute critical exponents for these models in the upper critical dimension d=4, and also below the critical dimension for long-range models. The lectures are based on collaborations with David Brydges and Roland Bauerschmidt.
SRQW01 6th September 2018
13:30 to 14:30
Felix Otto Regularity structures: Reconstruction and Integration - part 4
This minicourse is coordinated with the one of Lorenzo Zambotti. The joint goal is to treat the dynamical phi-4-3 model. This minicourse will provide the basic notions in regularity structures and discuss reconstruction and integration. It will mostly follow Martin Hairer's 2015 notes "Regularity structures and the dynamical phi-4-3 model''.
SRQW01 6th September 2018
14:30 to 15:30
Lorenzo Zambotti Renormalisation in regularity structures - part 4
This should be a mini-course on the algebraic side of the theory of regularity structures.
SRQW01 6th September 2018
16:00 to 17:00
Christoph Kopper The Flow equations of the renormalization group
The Flow equations in Polchinski's setting allow for a simple and transparent proof of perturbative renormalizability, cirumventing auxiliary combinatoric structures. They also permit to prove properties of perturbative Schwinger functions which are out of reach in other settings. The main problem for a nonperturbative analysis of those equations lies in their combinatoric instability, which is present already at the mean field level.
SRQW01 6th September 2018
17:15 to 18:15
Antti Kupiainen Wilsonian RG for SPDEs (Informal discussion)
SRQW01 7th September 2018
09:00 to 10:00
Roland Bauerschmidt Spectral gap critical exponent for Glauber dynamics of hierarchical spin models
We develop a renormalisation group approach to deriving the asymptotics of the spectral gap of the generator of Glauber type dynamics of spin systems at and near a critical point. In our approach, we derive a spectral gap inequality, or more generally a Brascamp--Lieb inequality, for the measure recursively in terms of spectral gap or Brascamp--Lieb inequalities for a sequence of renormalised measures. We apply our method to hierarchical versions of the $4$-dimensional $n$-component $|\varphi|^4$ model at the critical point and its approach from the high temperature side, and the $2$-dimensional Sine--Gordon and the Discrete Gaussian models in the rough phase (Kosterlitz--Thouless phase). For these models, we show that the spectral gap decays polynomially like the spectral gap of the dynamics of a free field (with a logarithmic correction for the $|\varphi|^4$ model), the scaling limit of these models in equilibrium. Co-author: Thierry Bodineau
SRQW01 7th September 2018
10:00 to 11:00
Gordon Slade Renormalisation group and critical phenomena - 4
The understanding of critical phenomena via the renormalisation group approach is one of the great achievements of theoretical physics during the last half of the previous century. This series of lectures will begin with an introduction to the critical behaviour of the phi^4 lattice spin system and its supersymmetric counterpart (the weakly self-avoiding walk). The lectures will mainly be occupied with an introduction to a rigorous renormalisation group method that has been developed and used to compute critical exponents for these models in the upper critical dimension d=4, and also below the critical dimension for long-range models. The lectures are based on collaborations with David Brydges and Roland Bauerschmidt.
SRQW01 7th September 2018
11:30 to 12:30
Gordon Slade Renormalisation group and critical phenomena - 3
The understanding of critical phenomena via the renormalisation group approach is one of the great achievements of theoretical physics during the last half of the previous century. This series of lectures will begin with an introduction to the critical behaviour of the phi^4 lattice spin system and its supersymmetric counterpart (the weakly self-avoiding walk). The lectures will mainly be occupied with an introduction to a rigorous renormalisation group method that has been developed and used to compute critical exponents for these models in the upper critical dimension d=4, and also below the critical dimension for long-range models. The lectures are based on collaborations with David Brydges and Roland Bauerschmidt.
SRQW01 7th September 2018
13:30 to 14:30
Massimiliano Gubinelli A stochastic approach to constructive QFT
Co-author: Nikolay Barashkov (University of Bonn)We propose a new existence proof of the Phi^4_{2,3} Euclidean quantum fields in a periodic domain using tools from stochastic analysis, in particular a stochastic control interpretation of Wilson's continuous RG.