General Relativity & Quantum Cosmology

the multi-scale entanglement renormalization ansatz (MERA) is a tensor network that efficiently represents the ground state wave-function of a lattice Hamiltonian. Similarly, its extension to the continuum, the continuous MERA [proposed by Haegeman, Osborne, Verschelde and Verstraete, Phys. Rev. Lett. 110, 100402 (2013), arXiv:1102.5524], aims to efficiently represent the vacuum state wave-functional of a quantum field theory. In this talk I will first review MERA and cMERA, with emphasis on why we should care about these two constructions, including their conjectured connection to the AdS/CFT correspondence. Then, using the simplified context of the free boson CFT in 1+1 dimensions, I will discuss two new results: (1) the cMERA wave-function, which has an explicit UV cut-off, is nevertheless invariant under the conformal group (but with modified Virasoro generators: the stress tensor is non-local at short distances); (2) cMERA can be regarded as an evolution in de Sitter space. Talk based on joint work with Qi Hu, in preparation.

The application of holography to fundamental problems in quantum gravity has been hindered by the lack of a solvable model. However, building on work by Sachdev and Ye, Kitaev has proposed a solvable QM system as a dual to an AdS2 black hole. I will discuss the model and its possible bulk interpretation.