Summing over geometries in string theory

A bstract We examine the question how string theory achieves a sum over bulk geometries with fixed asymptotic boundary conditions. discuss this problem help of tensionless on $$ {\mathrm{\mathcal{M}}}_3\times {\mathrm{S}}^3\times {\mathbbm{T}}^4 ℳ 3 × S T 4 (with one unit NS-NS flux) that was recently understood to be dual symmetric orbifold Sym N ( ). strengthen analysis [1] and show perturbative partition function around background already includes semi-classical large stringy corrections can interpreted as various geometries. argue in particular Euclidean wormhole geometry factorizes completely into factors associated two boundaries spacetime. Central is remarkable property moduli space integral localize covering spaces conformal ℳ 3 . also emphasize fact perturbation computes grand canonical family theories ⊕ The naturally expressed winding worldsheets, each which we interpret ‘stringy geometry’. condensate such briefly effect ensemble averaging Narain deforming away from by marginal deformation.