Between 4-8 October 2021, we held the online workshop ∀ Λ Holography@ Prague (All Lambda Holography at Prague), aiming to bring together researchers from the level of PhD students to senior researchers, working on Holography at different signs of the Cosmological Constant (Λ).
A spacetime with cosmological constant has constant curvature, be it positive, negative or zero. The negative cosmological constant corresponds to Anti de Sitter (AdS) spacetime which has negative curvature and describes a spacetime that contracts with an accelerated pace, the zero cosmological constant to Minkowski, which is the flat spacetime, and the positive cosmological constant corresponds to the de Sitter (dS) spacetime with positive curvature that expands with accelerated pace.
Some examples to where these geometries arise in nature are:
- AdS geometries (Λ<0) arises as the near horizon geometry of black holes.
- Most of our current understanding of standard model particles are set as quantum fields on Minkowski (Λ=0).
- dS geometry (Λ>0) has relevance for our universe at its primordial and current day states.
Holographic studies were initiated by analyzing gravitational theories on AdS and showed that these can be cast as conformal field theories, theories where the laws of physics remain invariant if lengths are rescaled. Eventually holography became a modern tool to understand gravity and the question whether it applies to other spacetimes besides AdS arose.
A uniting property of all these spacetimes with different signs of Λ is that they are all listed among maximally symmetric spacetimes, meaning each one of them posseses the maximum number of symmetries a spacetime can posses at a given number of dimensions. Yet for each one the types of symmetries involved are different, which leads to difference in their holographic properties and technicalities in investigating these properties.
The goal of the workshop was to bringing together experts on these three aspects of holography to discuss and exchange ideas leading towards its broader understanding. This became a very successful event as the participants voiced their appreciation of being exposed to different techniques and questions from Λ s other then theirs.