The Yes Boundaries Wavefunctions of the Universe and Late Time Cosmology

The topology of the universe is unknown, and a typical manifold will contain nontrivial cycles and boundaries.  This is quite consistent with the observed Lambda CDM cosmology, which does not imply that we live in a closed universe (including observers).   We start by briefly summarizing recently derived constraints on a population of timelike boundaries in the observable universe using recent CMB and BAO data, incorporating UV sensitive effects.  We then turn to their role in holography, where they incorporate a multiplicity of states.  In recent years this led to a concrete microstate count for the timelike-bounded de Sitter static patch in four dimensions, via a combination of solvable and fine-tuned deformations of AdS/CFT.  We next construct the thermofield double of the system to generate the cosmological future wedge in this framework.  We then show how to introduce constraints in this Hamiltonian system in order to capture tall states further down in the spectrum, where the boundaries are in causal contact. (We also note a separate method in progress for reaching the future wedge, deforming the timelike bounded theory to Cauchy slice holography.)