String Phenomenology: Past, Present and Future Perspectives

TL;DR

This paper reviews the development of string phenomenology, highlighting its role in connecting string theory to the Standard Model, recent discoveries in heterotic string models, and future research directions involving quantum gravity and cosmology.

Contribution

It provides a comprehensive overview of past and present string phenomenology research, including model classification, key discoveries, and future prospects in quantum gravity and cosmology.

Findings

Discovery of exophobic heterotic-string vacua

Observation of spinor-vector duality

Development of methods to classify large string models

Abstract

The observation of a scalar resonance at the LHC, compatible with perturbative electroweak symmetry breaking, reinforces the Standard Model parameterisation of all subatomic data. The logarithmic evolution of the SM gauge and matter parameters suggests that this parameterisation remains viable up to the Planck scale, where gravitational effects are of comparable strength. String theory provides a perturbatively consistent scheme to explore how the parameters of the Standard Model may be determined from a theory of quantum gravity. The free fermionic heterotic string models provide concrete examples of exact string solutions that reproduce the spectrum of the Minimal Supersymmetric Standard Model. Contemporary studies entail the development of methods to classify large classes of models. This led to the discovery of exophobic heterotic-string vacua and the observation of spinor-vector duality, which provides an insight to the global structure of the space of (2,0) heterotic-string vacua. Future directions entail the study of the role of the massive string states in these models and their incorporation in cosmological scenarios. A complementary direction is the formulation of quantum gravity from the principle of manifest phase space duality and the equivalence postulate of quantum mechanics, which suggest that space is compact. The compactness of space, which implies intrinsic regularisation, may be tightly related to the intrinsic finite length scale, implied by string phenomenology.