Speaker
Dr
Oliver Eyton-Williams
(Institute of Theoretical Physics, University of Warsaw, 00-681 Warsaw, Poland)
Description
The issue of fine-tuning necessary to achieve satisfactory degree of hierarchy
between moduli masses, the gravitino mass and the scale of the cosmological constant
has been revisited in the context of supergravities with consistent D-terms. We have
studied (extended) racetrack models where supersymmetry breaking and moduli
stabilisation cannot be separated from each other. We show that even in such cases
the realistic hierarchy can be achieved on the expense of a single fine-tuning. The
presence of two condensates changes the role of the constant term in the
superpotential, W_0, and solutions with small vacuum energy and large gravitino mass
can be found even for very small values of W_0. Models where D-terms are allowed to
vanish at finite vevs of moduli fields - denoted `cancellable' D-terms - and the ones
where D-terms may vanish only at infinite vevs of some moduli - denoted
`non-cancellable' - differ markedly in their properties. It turns out that the tuning
with respect to the Planck scale required in the case of cancellable D-terms is much
weaker than in the case of non-cancellable ones. We have shown that, against
intuition, a vanishing D-term can trigger F-term uplifting of the vacuum energy due
to the stringent constraint it imposes on vacuum expectation values of charged
fields. Finally we note that our models only rely on two dimensionful parameters: M_P
and W_0.
Author
Dr
Oliver Eyton-Williams
(Institute of Theoretical Physics, University of Warsaw, 00-681 Warsaw, Poland)
Co-authors
Dr
Radek Matyszkiewicz
(Institut fur Theoretische Physik, TU Dresden, Germany)
Dr
Zygmunt Lalak
(Institute of Theoretical Physics, University of Warsaw, 00-681 Warsaw, Poland)
