Theoretical and Phenomenological Aspects of Superstring Theories

TL;DR

This paper explores the effective field theories of heterotic superstring models, focusing on threshold corrections, moduli dependence, and one-loop effects in various orbifold compactifications, providing insights into gauge couplings and supersymmetry breaking.

Contribution

It presents new calculations of threshold corrections, moduli dependence, and one-loop effects in heterotic string orbifold models, including non-decomposable cases, advancing understanding of string phenomenology.

Findings

Calculated moduli dependence of threshold corrections in orbifold models

Identified Hauptmodul functions for relevant congruence subgroups

Derived one-loop corrections to the prepotential in N=2 heterotic compactifications

Abstract

We discuss aspects of the heterotic string effective field theories in orbifold constructions of the heterotic string. We calculate the moduli dependence of threshold corrections to gauge couplings in (2,2) symmetric orbifold compactifications. We perform the calculation of the threshold corrections for a particular class of abelian (2,2) symmetric non-decomposable orbifold models... internal twist is realized as generalized Coxeter automorphism. We define the limits for the existence of states causing singularities in the moduli space in the perturbative regime for a generic vacuum of the heterotic string. The 'proof' provides evidence for the explanation of the stringy 'Higgs effect'. Furthermore, we calculate the moduli dependence of threshold corrections as target space invariant free energies for non-decomposable orbifolds, identifying the Hauptmodul' functions for the relevant congruence subgroups. The required solutions provide for the \mu mass term generation in the effective low energy theory and affect the induced sypersymmetry breaking by gaugino condensation. In addition, we discuss the one loop gauge and gravitational couplings in (0,2) non-decomposable orbifold compactifications. In the second part of the Thesis the one loop correction to the Kahler metric for a generic N=2 orbifold compactification of the heterotic string is calculated... In this way, with the use of the one loop string amplitudes, the prepotential of the vector multiplets of the N=2 effective low-energy heterotic string is calculated in decomposable toroidal compactifications of the heterotic string ... This method provides the solution for the one loop correction to the prepotential of the vector multiplets of the heterotic string compactified on the K_3 \times T^2...