# nLab supersymmetry and Calabi-Yau manifolds

### Context

#### Gravity

gravity, supergravity

superalgebra

and

supergeometry

# Contents

## Idea

This page reviews some of the relation between the existence of supersymmetries in a spacetime quantum field theory which arises as the effective quantum field theory of some string 2d SCFT, the special geometry of that spacetime (such as Calabi-Yau manifold structure) as well as increased worldsheet supersymmetry of the superstring.

### Target space perspective

A solution to the bosonic Einstein equations of ordinary gravity – some Riemannian manifold – has a global symmetry if it has a Killing vector.

Accordingly, a configuration that solves the supergravity Euler-Lagrange equations is a global supersymmetry if it has a Killing spinor: a covariantly constant spinor.

(Here the notion of covariant derivative includes the usual Levi-Civita connection, but also in general torsion components and contributions from other background gauge fields such as a Kalb-Ramond field and the RR-fields in type II supergravity or heterotic supergravity.)

Of particular interest to phenomenologists around the turn of the millenium (but maybe less so today with new experimental evidence) has been in KK-compactification solutions of spacetime manifolds of the form $M^4 \times Y^6$ for $M^4$ the locally observed Minkowski spacetime (that plays a role as the background for all available particle accelerator experiments) and a small closed 6-dimensional Riemannian manifold $Y^6$.

In the absence of further fields besides gravity, the condition that such a configuration has precisely one Killing spinor and hence precisely one global supersymmetry turns out to tbe precisely that $Y^6$ is a Calabi-Yau manifold. One such remaining global supersymmetry in the lowe energy effective field theory in 4-dimensions is or was believed to be of relevance in phenomenology, see for instance the supersymmetric MSSM extension of the standard model of particle physics. This is where all the interest into these Calaboi-Yau manifolds in string theory comes from. (Notice though that nothing in the theory itself demands such a compactification. It is only the phenomenological assumption of the factorized spacetime compactification together with $N = 1$ supersymmetry that does so).

More generally, in the presence of other background gauge fields, the Calabi-Yau condition here is deformed. One also speaks of generalized Calabi-Yau spaces. (For instance (GMPT05)).

Alternatively, if one starts the KK-compactification not from 10-dimensional string theory but from 11-dimensional supergravity/M-theory, then the condition for the KK-compactification to preserved precisely one global supersymmetry is that it be on a G2-manifold. For more on this see at M-theory on G2-manifolds.

### Worldvolume perspective

On the other hand, the enhanced supersymmetry of target space is also reflected in enhanced supersymmetry on the worldsheet of the string. For instance for the heterotic string whose worlsheet 2d SCFT apriori has $N=(1,0)$ supersymmetry, the target space theory has $N=1$ supersymmetry precisely if the worldsheet theory’s supersymmetry enhanced to $N=(2,0)$. (BDFF 88). For more on this see at 2d (2,0)-superconformal QFT.

Similar comments apply to type II superstring theory, where $N=1$ target space supersymmetry enhanced the worldheet symmetry from $N=(1,1)$ to $N=(2,2)$. This is reflected notably in the mirror symmetry of the targt Calabi-Yau manifolds.

## References

Original references include

and chapters 12 - 16 of

A canonical textbook reference for the role of Calabi-Yau manifolds in compactifications of 10-dimensional supergravity is

Lecure notes in a more general context of string phenomenology include

Discussion of generalized Calabi-Yau backgrounds is for instance in

• Mariana Graña, Ruben Minasian, Michela Petrini, Alessandro Tomasiello, Generalized structures of $N=1$ vacua (arXiv:hep-th/0505212)

Revised on September 25, 2014 15:39:01 by David Corfield (129.12.18.81)