Strings through the Microscope

TL;DR

This paper provides an overview of modern string theory, focusing on dualities, boundary conformal field theory, and recent developments in non-rational and non-unitary models, highlighting ongoing research challenges and directions.

Contribution

It introduces the fundamental ingredients of modern string theory and discusses recent advances in boundary conditions and non-rational conformal field theories.

Findings

Classification and construction of boundary conditions

Studies of 2D renormalization group flows

Research on non-rational and non-unitary conformal field theories

Abstract

Over the last few years, string theory has changed profoundly. Most importantly, novel duality relations have emerged which involve gauge theories of brane excitations on one side and various closed string backgrounds on the other. In this lecture, we introduce the fundamental ingredients of modern string theory and explain how they are modeled through 2D (boundary) conformal field theory. This so-called `microscopic description' of strings and branes is an active research area with new results ranging from the classification and construction of boundary conditions to studies of 2D renormalization group flows. We shall provide an overview of such developments before concluding the lecture with an extensive outlook on some research that is motivated by current problems in string theory. This includes investigations of non-rational and non-unitary conformal field theories.