Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas 2020-Foreword

2020 was a special year. This was said repeatedly, but is certainly the right name for the 2020 edition of the Joint Varenna-Lausanne International Workshop on the Theory of Fusion Plasmas. After it became clear that Covid-19 was not going to give up easily, the conference was postponed from August to October 12-16 and the venue was changed too. The conference finally took place in the cosy Starling Hotel in Lausanne. The format was hybrid, a mix of face-to-face and remote participation. This was the result of tremendous efforts from the organisers, who had to adapt on a day-to-day basis in a context of fast evolving health situation. We believe the result was up to the dedication. Discussions were lively thanks to a very high quality of presentations and a relatively large audience, although the attendance was slightly reduced due to the circumstances. The hybrid format was really a plus. It allowed a rich mixture of exchanges on site and remote discussions by teleconference. Poster sessions by videoconferencing were a real success, including group participation and chats - the massive participation of young (and less young) Swiss scientists on site was surely appreciated. So once again, theory was innovative! MHD was in the limelight, covering all hot topics at stake in present and future fusion devices: disruptions, Edge Localised Modes, error fields and Resonant Magnetic Perturbations, Neoclassical Tearing Modes, magnetic configuration with negative triangularity, kinetic MHD, and last but not the least, 3D magnetic equilibria with applications to tokamaks and stellarators. This was a firework of theoretical and numerical results. Turbulent transport was on the forefront too, with some focus this year on plasma edge issues, turbulence self-organisation and transport in stellarators. Finally, special attention was given to impurity transport, in line with a continued interest in metallic walls. Mathematics and computer sciences applied to numerical simulations for plasma physics are traditionally lively topics of the conference, and indeed, outstanding results were presented both in fluid and kinetic computing. List of Scientific Committee are available in this pdf.