Special geometries, such as Calabi-Yau manifolds, play a central role in multiple areas of string theory, as well as gravitational theories more generally. The goal of these lectures is to introduce some of the formalism and tools useful for characterising such geometries, pitched at the level of a starting PhD student. We will start with purely geometrical backgrounds using the general notions of a G-structure and special holonomy and then will go on to describe backgrounds that also have non-trivial fluxes. We will be guided by applications to string phenomenology and the AdS/cft correspondence.

“Special” geometries, such as Calabi-Yau manifolds, play a central role in multiple areas of string theory, as well as gravitational theories more generally. The goal of these lectures is to introduce some of the formalism and tools useful for characterising such geometries, pitched at the level of a starting PhD student. We will start with purely geometrical backgrounds using the general notions of a G-structure and special holonomy and then will go on to describe backgrounds that also have non-trivial fluxes. We will be guided by applications to string phenomenology and the AdS/cft correspondence.

Special geometries, such as Calabi-Yau manifolds, play a central role in multiple areas of string theory, as well as gravitational theories more generally. The goal of these lectures is to introduce some of the formalism and tools useful for characterising such geometries, pitched at the level of a starting PhD student. We will start with purely geometrical backgrounds using the general notions of a G-structure and special holonomy and then will go on to describe backgrounds that also have non-trivial fluxes. We will be guided by applications to string phenomenology and the AdS/cft correspondence.

We show how "generalised geometry", a class of extensions of conventional differential geometry first introduced by Hitchin, gives a natural way of formulating supergravity theories. The formulation unifies the bosonic fields and symmetries and has a natural action of O(d,d) or the exceptional groups E_d in d-dimensions. By introducing the analogue of the Levi-Civita connection we find that full set of bosonic equations of motion reduce to simply the vanishing of the generalised Ricci tensor. We show that the connection also encodes the supersymmetry variations and fermionic equations of motion. This formalism also gives natural extensions of complex, symplectic and other integrable structures, with implications for describing supersymmetric string theory backgrounds.