New frontiers of integrable deformations

Quantum field theory (QFT) is one of the most successful frameworks for studying a wealth of physical phenomena, ranging from the interactions of fundamental particles to condensed-matter systems. It is an ongoing challenge to understand quantum field theories exactly, i.e. without resorting to perturbation theory. A historically successful strategy is to restrict to theories simple enough to be exactly solvable, yet non-trivial enough to capture interesting physics. In the case of interacting quantum field theories, exactly solvable models can most often be found in two dimensions. These can be divided in two families: two-dimensional conformal field theories (CFTs), and two-dimensional integrable quantum field theories (IQFTs). Unsurprisingly in view of their very constrained nature, these theories are like rare gems: as precious for advancing our understanding as they are hard to find. It is therefore natural to ask, given an exactly solvable theory, whether it is possible to deform it, perhaps spoiling some of its symmetries, but preserving its exact solvability.

Recently integrable deformations stemming from composite operators constructed out of two conserved currents attracted much attention. Perhaps the most striking example of such deformations is given by the so-called T-Tbar deformations, which are constructed out of the product of two components of the stress-energy tensor. These deformations, first introduced by A.B. Zamolodchikov in 2004, were studied in detail by Zamolodchikov & Smirnov and by R. Tateo and collaborators in 2016. It was understood that the flow that they generate preserves exact solvability of a theory, and acts in a simple way on the spectrum. Moreover, these deformations appear naturally in string theory and seem to allow for a gravitational interpretation. In parallel, there has been remarkable activity in the study of integrable deformations of string-theory backgrounds and supersymmetric non-linear sigma model, in particular in the framework of “Yang-Baxter deformations”. While conceptually separate, many interesting similarities between these two frameworks are emerging. Many aspects remain to be explored, especially concerning the geometrical and gravitational (or string-theoretical) interpretation of these deformation, their application to non-linear sigma models, Wess-Zumino-Novikov-Witten models, as well as their role in the AdS/CFT correspondence and. The goal of this workshop is to bring together experts in all these topics for an open exchange of ideas, which we expect will lead to new collaborations and interesting results across all these fields.

• Riccardo Conti (U Torino)
• Andrea Dei (ETH Zurich)
• Fotis Farakos (KU Leuven)
• Christian Ferko (U Chicago)
• Guzmán Hernández-Chifflet (U New York)
• Hongliang Jiang (U Bern)
• Stefano Negro (U Stony Brook)
• Domenico Orlando (INFN Torino)
• Tomas Prochazka (LMU Munich)
• Susanne Reffert (U Bern)
• Fiona Seibold (ETH Zurich)
• Alessandro Sfondrini (ETH Zurich)
• Edgar Shaghoulian (U Cornell)
• Gabriele Tartaglino-Mazzucchelli (U Bern & U Queensland)
• Stijn van Tongeren (HU Berlin)
• Pelle Werkman (U Groeningen)
• Linus Wulff (MU Brno)

Villa Garbald is a facility of ETH Zurich, but is not located in Zurich. Rather it is right on the border with Italy, between Chiavenna and Bregaglia. It takes little less than 5 hours to get there from Zurich, and little less than 4 from Milan (by public transport; coming by car takes 3h and 2h30, respectively).

• From Zurich by public transport it is necessary to go to Chur, change train to St Moritz and take a public bus (bus n. 4 in direction "Chiavenna") from St Moriz to the conference venue (stop "Castasegna - Vecchia Dogana").
• From Milano by public transport, it is necessary to reach Chiavenna, which can be done by train with a change in Colico. From there, one should continue by public bus (bus n. 4 in direction "St Moritz") from Chiavenna to the conference venue (stop "Castasegna - Vecchia Dogana").
• Participants coming from north of Switzerland can also go directly to Chur by train or by long-distance bus and continue to St Moritz - Castasegna.

For information on local travel in Switzerland see www.sbb.ch. Since reaching Castasegna from the main Swiss airports and cities require a relatively long trip, we advise participants to consider purchasing a one-day travelcard, which is relaticely cheap (if bought in advance) and valid on all trains and buses (and most boats) in Switzerland.

For long-distance buses to Zurich and Chur see e.g. www.flixbus.ch. For local trains in Lombardia (the Milano region) see www.trenord.it.

Alessandro Sfondrini (ETH Zurich).