Heterotic free fermionic and symmetric toroidal orbifold models

Abstract

Free fermionic models and symmetric heterotic toroidal orbifolds both constitute exact backgrounds that can be used effectively for phenomenological explorations within string theory. Even though it is widely believed that for Z 2 × Z 2 orbifolds the two descriptions should be equivalent, a detailed dictionary between both formulations is still lacking. This paper aims to fill this gap: we give a detailed account of how the input data of both descriptions can be related to each other. In particular, we show that the generalized GSO phases of the free fermionic model correspond to generalized torsion phases used in orbifold model building. We illustrate our translation methods by providing free fermionic realizations for all Z 2 × Z 2 orbifold geometries in six dimensions.

Niemeier Lattices in the Free Fermionic Heterotic–String Formulation

“…They correspond to 2 × 2 toroidal orbifold constructions at special points in the moduli space [49,[52][53][54][55][56][57]. Their phenomenological properties raise the possibility that the true string vacuum shares some of their underlying properties.…”

GUT precursors and entwined SUSY: The phenomenology of stable nonsupersymmetric strings

“…In this way, it might even be possible to bring M GUT significantly below the traditional unification scale. Continuing to identify M s with M GUT would then lead to a self-consistent scenario in which M s ≪ 10 16 GeV, with R −1 correspondingly reduced even further, perhaps even all the way into the TeV range. Indeed, taking R −1 ≈ 1 TeV within Eq.…”

“…[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]). This growing literature indicates an increasing interest in this subject, presumably motivated not only by the apparent experimental absence of supersymmetry at the Large Hadron Collider but also by the intrinsically different theoretical behavior of strings within this hitherto largely unexplored region of the string landscape.…”

LHC di-photon excess and gauge coupling unification in extra $$Z^\prime $$ Z ′ heterotic-string derived models

“…Phenomenological string models constructed in the so called fermionic formulation [138][139][140]155,156,[165][166][167][168][169][170][171] correspond to Z 2 ×Z 2 orbifolds at enhanced symmetry points in the toroidal moduli space [172][173][174][175][176]. These models reproduce the main characteristic of the Standard Model spectrum, i.e.…”