Browsing by Author "Valandro, Roberto"

Now showing 1 - 4 of 4
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    Fixing Moduli in Exact Type IIA Flux Vacua
    (2006-09-07T10:55:18Z) Acharya, Bobby Samir; Benini, Francesco; Valandro, Roberto; Physics; Elementary Particle Theory
    Type IIA flux compactifications with O6-planes have been argued from a four dimensional effective theory point of view to admit stable, moduli free solutions. We discuss in detail the ten dimensional description of such vacua and present exact solutions in the case when the O6-charge is smoothly distributed. In the localised case, the solution is a half-flat, non-Calabi-Yau metric. Finally, using the ten dimensional description we show how all moduli are stabilised and reproduce precisely the results of de Wolfe et al.
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    Statistics of M theory vacua
    (2005) Acharya, Bobby Samir; Denef, Frederik; Valandro, Roberto; Physics; Elementary Particle Theory
    We study the vacuum statistics of ensembles of M theory compactifications on G2 holonomy manifolds with fluxes, and of ensembles of Freund-Rubin vacua. We discuss similarities and differences between these and Type IIB flux landscapes. For the G2 ensembles, we find that large volumes are strongly suppressed, and for both, unlike the IIB case, the distribution of cosmological constants is non-uniform. We also argue that these ensembles typically have exponentially more non-supersymmetric than supersymmetric vacua, and show that supersymmetry is virtually always broken at a high scale.
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    Suppressing Proton Decay in Theories with Localised Fermions
    (2005) Valandro, Roberto; Acharya, Bobby Samir; Physics; Elementary Particle Theory
    We calculate the contribution to the proton decay amplitude from Kaluza-Klein lepto-quarks in theories with extra dimensions, localised fermions and gauge fields which propagate in the bulk. Such models naturally occur within the context of M-theory. In SU(5) models we show that carefully including all such modes gives a distinctive pattern of decays through various channels including a strong suppression of decays into neutrinos or right handed positrons. By contrast there is no such suppression for SO(10).
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    Warped Models in String Theory
    (2007-01-31T13:53:07Z) Acharya, Bobby Samir; Benini, Francesco; Valandro, Roberto; Physics; Elementary Particle Theory
    Warped models, originating with the ideas of Randall and Sundrum, provide a fascinating extension of the standard model with interesting consequences for the LHC. We investigate in detail how string theory realises such models, with emphasis on fermion localisation and the computation of Yukawa couplings. We find, in contrast to the 5d models, that fermions can be localised anywhere in the extra dimension, and that there are new mechanisms to generate exponential hierarchies amongst the Yukawa couplings. We also suggest a way to distinguish these string theory models with data from the LHC.