**Short description**

The first week of the Institute will primarily focus on non-perturbative topological string theory, refinement, exact quantisation and matrix models, while the second week will deal with B-type topological string theory, open-closed mirror symmetry and categories of matrix factorisations. One of the goals of the second week is to bring together researchers in both Mathematics and Physics.

This informal workshop will have just 2-3 talks per day to allow for extensive discussions and collaboration. It is supported jointly by CERN and by the Korean government under the CERN-Korea Collaboration agreement. It is also supported by the IBS Center for Geometry and Physics, Korea.

**Organisers**: Ahmad Zein Assi, Alba Grassi, Cheol-Hyun Cho, Calin Lazaroiu, Sangmin Lee, Wolfgang Lerche, Marcos Marino, Nikita Nekrasov, Yong-Geun Oh and Johannes Walcher.

**Key speakers**:

1st week: A. Klemm, K. S. Narain, R. Schiappa

2nd week: C.-H. Cho, J.-S. Park and J. Solomon

**Practical information**: There is no registration fee, and participation is open except for limited desk space. A limited number of rooms have already been pre-booked at CERN hotels, please contact THworkshops.secretariat@cern.ch (after registration) if you want to stay there during the meeting.

**Registration**: Closed

**Extended description**

Topological string theory has played an important role in the past decades in inducing a deeper understanding of string theory, but has also led to a plethora of new results and applications both in mathematics and physics.

From the mathematical point of view, this theory is deeply related to matrix models, arithmetic and integrability, spectral theory, supersymmetric gauge theories, Painlevé equations, knot theory and homological mirror symmetry. These relations have been exploited in recent years leading to important developments in these fields. For instance it has been possible to compute exactly and explicitly the spectrum of a new class of operators and integrable systems or to analyse in detail certain non-perturbative effects in supersymmetric gauge and string theories, and matrix models. Important progress has also been made in understanding topological open string invariants via mirror symmetry.

On the other hand, from the physical point of view, topological string theory has had a direct impact on the understanding of the physical string theory from which it can be constructed. Indeed, it can be viewed as a toy model for string theory probing its BPS sector only. For example, it has been shown that the partition function of topological string theory computes a class of higher derivative gravitational couplings in the string effective action. At low energies, this connection has led to new insights into Seiberg-Witten theory and its deformations. In a similar vein, there is still a number of interesting problems and challenges, one of which is to provide a clear worldsheet definition of the refined topological string and its applications to the physics of black holes.

The goal of the institute is to bring together mathematicians and physicists working on topics related to topological string theory and to give an overview of the recent developments over the last years. This will help in fostering new collaborations by providing a stimulating environment to make further advancements in the field.