3 research outputs found
Revisiting Coupling Selection Rules in Heterotic Orbifold Models
We study L-point couplings between twisted sector fields in heterotic
orbifold compactifications, using conformal field theory. Selection rules
provide an easy way to identify which couplings are non-vanishing. Those used
in the current literature are gauge invariance, R-charge conservation and the
space group selection rule, but they are not the whole story. We revive and
refine a fourth selection rule, due to symmetries in the underlying torus
lattice, and introduce a fifth one, due to the existence or not of classical
worldsheet instanton solutions to mediate the couplings. We consider briefly
the phenomenological consequences of the additional rules, in particular for
recent orbifold constructions whose field content correspond to that of the
MSSM. The structure of the exotic mass matrices is unaltered and many
dimension-5 proton-decay operators vanish.Comment: 27 pages, v2: several clarifications, matches JHEP version. v3:
supercedes journal version, erratum to appear in JHEP; correction to "rule 5"
equations, main ideas unchange
On Moduli Stabilisation and de Sitter Vacua in MSSM Heterotic Orbifolds
We study the problem of moduli stabilisation in explicit heterotic orbifold
compactifications, whose spectra contain the MSSM plus some vector-like exotics
that can be decoupled. Considering all the bulk moduli, we obtain the 4D low
energy effective action for the compactification, which has contributions from
various, computable, perturbative and non-perturbative effects. Hidden sector
gaugino condensation and string worldsheet instantons result in a combination
of racetrack, KKLT and cusp-form contributions to the superpotential, which
lift all the bulk moduli directions. We point out the properties observed in
our concrete models, which tend to be missed when only "generic" features of a
model are assumed. We search for interesting vacua and find several de Sitter
solutions, but -- so far -- they all turn out to be unstable.Comment: 55 pages, 2 figures, v2: added link to mathematica files, other minor
revisions, matches JHEP versio