129 research outputs found
Lack of trinification in Z_3 orbifolds of the SO(32) heterotic string
We report results relating to the trinification scenario in some explicit
string constructions that contain SU(3)^3 as a gauge symmetry. These models are
obtained from symmetric Z_3 orbifolds of the SO(32) heterotic string with one
discrete Wilson line. We highlight the obstacles that were encountered: the
absence of the usual Higgs sector that would break SU(3)^3 \to SU(3)_c \times
SU(2)_L \times U(1)_Y; the presence of exotics that would generically befoul
gauge coupling unification and lead to fractionally-charged states in the low
energy spectrum.Comment: 1+7 pages, comments and refs adde
D-Moduli Stabilization
The matter sector of four-dimensional effective supergravity models obtained
from the weakly coupled heterotic string contains many moduli. In particular,
flat directions of the D-term part of the scalar potential in the presence of
an anomalous U(1) give rise to massless chiral multiplets which have been
referred to elsewhere as D-moduli. The stabilization of these moduli is
necessary for the determination of the large vacuum expectation values of
complex scalar fields induced by the corresponding Fayet-Illiopoulos term. This
stabilization is of phenomenological importance since these background values
determine the effective theory below the scale of the anomalous U(1) symmetry
breaking. In some simple models we illustrate the stabilization of these moduli
due to the nonperturbative dynamics associated with gaugino condensation in a
hidden sector. We find that background field configurations which are stable
above the condensation scale no longer represent global minima once dynamical
supersymmetry breaking occurs. The implications for low energy models based on
promising ``flat'' directions are discussed.Comment: 11 pages, talk given at Superstring Phenomenology Conference, Oxford,
England, July 7, 200
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