Morning lectures
Topological phases do not fall into the Laudau's paradigm of symmetry breaking. The absence of local order parameter to characterize these phases has motivated the development of new ways to probe them. Among those new approaches, entanglement measurements and characterizations have allowed a deeper understanding of these systems.
Using concrete examples such as the Su-Schrieffer-Heeger or the AKLT models, we will illustrate several concepts of quantum information applied to topological matter. In particular, we will unveil how the edge excitations, a key signature of topological phases, are encoded within the bulk groundstate, giving flesh to the bulk-edge correspondence.
Conformal invariance is a fundamental symmetry in nature and has been studied in Physics since the introduction of the Maxwell equations.
Conformal transformations are the angle-preserving transformations. In general dimension, the conformal group is composed by the Poincaré group (translations and rotations) plus dilations and inversions. Among the most recent breakthrough results in theoretical physics, one has shown that, in any dimension, the constraints coming from conformal invariance together with general consistency assumptions can be sufficient to provide non-perturbative and beyond mean field theory results for strongly interacting systems. For instance, this approach has provided the critical exponents of the critical 3D Ising model.
In two dimension the group of conformal transformations becomes infinite, thus opening the way for a series of powerful analytical approaches. For instance the analytic behavior of the symmetry functions of the 2d conformal group, called the conformal blocks, have been at the basis of the first prediction of non-Abelian statistics in fractional quantum Hall systems.
In these lectures, I will introduce to the basic concepts concerning the implementation of conformal symmetry at quantum level and the functions that appear in this theory. I will in particular stress the relation between the topological states in 2D and the quantum conformal symmetry. New directions of research will be also discussed.
Raoul's lecture notes: lecture notes 1, lecture notes 2, lecture notes 3.Topological order is a form of order which cannot be characterized locally (such as for symmetry breaking) and in which the entanglement in the system organizes in a global way. In my lectures, I will discuss a number of important examples which exhibit topological order. In particular, Kitaev's Toric Code model will be presented in detail, including its ground space structure and the nature of its excitations. In the second part of the lecture, I will explain how Tensor Networks provide an entanglement-based perspective on systems with complex entanglement, which allows for a simple local characterization of systems with topological order and allows us to extend the description above to a larger class of models.
Norbert's lecture notes: lecture notes 1, lecture notes 2.Afternoon lectures
Poster session