Heterotic String Models in Curved Spacetime

TL;DR

This paper investigates four-dimensional heterotic string models in curved spacetime, demonstrating their consistency and classifying models with gauge groups resembling the Standard Model, potentially explaining particle families.

Contribution

It introduces a framework for constructing consistent four-dimensional heterotic string theories in curved spacetime using non-compact current algebra cosets, expanding string model possibilities.

Findings

Gauge groups include the Standard Model symmetries.

Models predict multiple families of quarks and leptons.

Consistent models are classified based on coset constructions.

Abstract

We explore the possibility of string theories in only four spacetime dimensions without any additional compactified dimensions. We show that, provided the theory is defined in curved spacetime that has a cosmological interpration, it is possible to construct consistent heterotic string theories based on a few non-compact current algebra cosets. We classify these models. The gauge groups that emerge fall within a remarkably narrow range and include the desirable low energy flavor symmetry of $SU(3)\times SU(2)\times U(1)$. The quark and lepton states, which come in color triplets and $SU(2)$ doublets, are expected to emerge in several families.