WI Seminar- Alejandro Vilar Lopez

Euclidean wormholes in holographic path integrals prepare states containing closed universes, but understanding these saddles from the microscopic point of view remains challenging. Recent constructions in AdS/CFT have sharpened this tension by identifying CFT states whose semiclassical bulk description appears to contain a closed universe. After briefly reviewing these examples and their relation to more standard two-boundary wormholes, I will turn to a SYK construction where the emergence of a wormhole can be studied directly from the microscopic theory. This provides a controlled setting to ask how microscopic correlations give rise to a smooth closed universe geometry, and what survives of this picture before ensemble averaging. I will conclude by discussing what these examples teach us, and what they still leave unresolved, about closed universes in holography.