CMT Forum: Lakshya Bhardwaj

I will discuss how Symmetry Topological Field Theories (SymTFTs), also known as topological holography, can be used to determine phases for systems carrying arbitrary, possibly categorical (i.e. non-invertible), global symmetry. This includes gapped phases and gapless phases lying at phase transitions between the gapped phases. The formalism is rather constructive:the knowledge of simple phase transitions like the ones provided by critical Ising and Potts models is used to construct transitions for arbitrarily large categorical symmetries. The main tool is the club sandwich configuration of SymTFT that performs non-invertible duality or KT (Kennedy-Tasaki) transformations on known phase transitions to construct new unknown phase transitions. Along the way, I will also describe how the same formalism can be used to construct all gapless SPT phases protected by any categorical symmetry. 
(Based on joint works with Lea Bottini, Daniel Pajer and Sakura Schafer-Nameki at Oxford: 2312.17322, 2310.03786 and 2310.03784)