Orbifold Symmetry Reductions of Massive Boson-Fermion Degeneracy

TL;DR

This paper explores string vacua with Massive Spectrum Degeneracy Symmetry (MSDS) in orbifold constructions, classifies possible Z_2^N-orbifolds with MSDS, and constructs models exhibiting this symmetry with distinct massless boson and fermion counts.

Contribution

It provides a classification of all Z_2^N-orbifolds with MSDS in free fermionic models and constructs explicit 2D models demonstrating RMSDS due to orbifold projections.

Findings

Models exhibit massive boson-fermion degeneracy with differing massless spectra.

MSDS models are distinct from supersymmetric theories due to n(b) neq n(f).

Connections to higher-dimensional gauged supergravity via marginal deformations.

Abstract

We investigate the existence of string vacua with Massive Spectrum Degeneracy Symmetry (MSDS) in Heterotic and Type II orbifold constructions. We present a classification of all possible Z_2^N-orbifolds with MSDS symmetry that can be constructed in the formalism of the 2d free fermionic construction. We explicitly construct several two-dimensional models whose Reduced Massive Spectrum Degeneracy Symmetry (RMSDS) is due to a set of Z_2-orbifold projections induced naturally in the framework of the free fermionic construction. In all proposed models the massive boson and fermion degrees of freedom exhibit Massive Spectrum Degeneracy Symmetry while the number of massless bosons n(b) and massless fermions n(f) are different; n(b) neq n(f). This property distinguishes the MSDS Z_2-twisted theories from ordinary supersymmetric ones. Some comments are stated concerning the large marginal (J x barJ)-deformations of the proposed models connecting them to higher-dimensional gauged-supergravity theories with non-trivial geometrical fluxes.