Explore the intricacies of tensionless string theory in this comprehensive High Energy Theory Seminar presented by Lorenz Eberhardt, a Member of the School of Natural Sciences at the Institute for Advanced Study. Delve into the complex world of partition functions, beginning with an introduction and overview of the speaker's approach. Gain insights into various backgrounds, super analogs, and conical defects before examining multiple boundaries in the context of string theory. Investigate the hybrid formalism and its applications, followed by an in-depth analysis of tau partition functions and grand canonical partition functions. Conclude with a detailed exploration of T4 partition functions, providing a thorough understanding of this advanced topic in theoretical physics.