\section*{Acknowledgements}
 
The work of G.D. was supported by Humboldt Foundation under Alexander von Humboldt Professorship,  by European Commission  under 
the ERC Advanced Grant 226371 and ERC Advanced Grant 339169 ``Selfcompletion'',   by TRR 33 \textquotedblleft The Dark
Universe\textquotedblright\   and  by the NSF grant PHY-0758032. 
The work of C.G. was supported in part by Humboldt Foundation and by Grants: FPA 2009-07908, CPAN (CSD2007-00042) and HEPHACOS P-ESP00346 and by the ERC Advanced Grant 339169 ``Selfcompletion'' .

It is a pleasure to thank organizers of  the New York meeting under the project ``The Particle Physics and Cosmology of Supersymmetry  and String Theory", where some of our results were presented.   






    
    
    
    