B-L Cosmic Strings in Heterotic Standard Models

TL;DR

This paper explores the formation and properties of B-L cosmic strings within heterotic string models that resemble the Minimal Supersymmetric Standard Model, analyzing their potential superconductivity and stability.

Contribution

It demonstrates the existence of B-L cosmic strings in heterotic models and analyzes their superconducting properties through numerical methods.

Findings

Boson condensates can form in these theories.

Weak couplings prevent bosonic superconductivity.

Electroweak phase transition inhibits fermionic superconductivity.

Abstract

E_{8} X E_{8} heterotic string and M-theory, when compactified on smooth Calabi-Yau manifolds with SU(4) vector bundles, can give rise to softly broken N=1 supersymmetric theories with the exact matter spectrum of the MSSM, including three right-handed neutrinos and one Higgs-Higgs conjugate pair of supermultiplets. These vacua have the SU(3)_{C} X SU(2)_{L} X U(1)_{Y} gauge group of the standard model augmented by an additional gauged U(1)_{B-L}. Their minimal content requires that the B-L symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed sneutrino. The soft supersymmetry breaking operators can induce radiative breaking of the B-L gauge symmetry with an acceptable B-L/electroweak hierarchy. In this paper, it is shown that U(1)_{B-L} cosmic strings occur in this context, potentially with both bosonic and fermionic superconductivity. We present a numerical analysis that demonstrates that boson condensates can, in principle, form for theories of this type. However, the weak Yukawa and gauge couplings of the right-handed sneutrino suggests that bosonic superconductivity will not occur in the simplest vacua in this context. The electroweak phase transition also disallows fermion superconductivity, although substantial bound state fermion currents can exist.