A Novel Superstring in Four Dimensions and Grand Unification

TL;DR

This paper constructs a four-dimensional superstring model with supersymmetry, modular invariance, and a pathway to the Standard Model, including neutrino mass predictions.

Contribution

It introduces a novel four-dimensional superstring model with Majorana fermions, achieving supersymmetry and connecting to the Standard Model via symmetry breaking.

Findings

Decoupling of tachyonic ground state

Realization of Standard Model gauge group

Predicted tau neutrino mass of about 1/25 eV

Abstract

A string in four dimensions is constructed by supplementing it with forty four Majorana fermions. The central charge is 26. The fermions are grouped in such a way that the resulting action is supersymmetric. The energy momentum and current generators satisfy the super-Virasoro algebra. The tachyonic ground state decouples from the physical states. GSO projections are necessary for proving modular invariance. Space-time supersymmetry provides reasons to discard the tachyons and is substantiated for modes of zero mass. The symmetry group of the model descends to the low energy standard model group $SU (3) \times SU_L (2) \times U_Y (1)$ through the Pati-Salam group. Left right symmetry is broken spontaneously and the mass of the tau neutrino is calculated to be about 1/25 electron volt.