Radiative fermion masses in local D-brane models
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In the context of D-brane model building, we present a realistic framework
for generating fermion masses that are forbidden by global symmetries. We show
that the string theoretical Large volume scenario circumvents the standard lore
that fermion masses generated by loop effects are too small in generic gravity
mediated scenarios. We argue that the fact that in toric singularity models,
the up quark masses have always a zero eigenvalue, corresponding to the
lightest generation, is due to the presence of approximate global symmetries
that we explicitly identify in del Pezzo singularities. These symmetries are
broken by global effects and therefore proportional to inverse powers of the
volume. We estimate the generic size of radiative corrections to fermion masses
in different phenomenological manifestations of the Large volume scenario.
Concrete realizations in terms of flavor violating soft-terms are estimated and
contrasted with current bounds on flavour changing neutral currents.
Contributions from generic extra Higgs-like fields set bounds on their masses
close to the GUT scale to produce realistic fermion masses.
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