Ohsawa–Takegoshi L2 extension theorem

The Ohsawa–Takegoshi L² extension theorem is a significant result in complex analysis, particularly in the theory of several complex variables. It provides conditions under which holomorphic functions defined on a submanifold can be extended to a larger domain while retaining certain properties, such as being in the L² space. More precisely, the theorem addresses the problem of extending holomorphic functions that are square-integrable on certain subvarieties of complex manifolds.