74 research outputs found
Beyond Twisted Tori
Exploiting the fact that Kaluza-Klein monopoles and the associated
generalized orbifold planes are sources for geometrical fluxes, omega, we show
that the standard constraint omega.omega=0, valid for superstring
compactifications on twisted tori, can be consistently relaxed. This leads to
novel possibilities for constructing superstring models with fluxes and
localized sources, as well as for stabilizing moduli. This also explains the
ten-dimensional origin of a family of N=4 gauged supergravities, whose
interpretation in type-IIA orientifold compactifications was lacking.Comment: 12 page
Mini-Split
The lack of evidence for new physics beyond the standard model at the LHC
points to a paucity of new particles near the weak scale. This suggests that
the weak scale is tuned and that supersymmetry, if present at all, is realized
at higher energies. The measured Higgs mass constrains the scalar sparticles to
be below 10^5 TeV, while gauge coupling unification favors Higgsinos below 100
TeV. Nevertheless, in many models gaugino masses are suppressed and remain
within reach of the LHC. Tuning the weak scale and the renormalization group
evolution of the scalar masses constrain Split model building. Due to the small
gaugino masses, either the squarks or the up-higgs often run tachyonic; in the
latter case, successful electroweak breaking requires heavy higgsinos near the
scalar sparticles. We discuss the consequences of tuning the weak scale and the
phenomenology of several models of Split supersymmetry including anomaly
mediation, U(1)_(B-L) mediation, and Split gauge mediation.Comment: 26 pages, 12 figures; v2:discussion and figure on the status of
fine-tuning in SUSY added, pheno section extende
Higgs mass determination in supersymmetry
We present the state-of-the-art of the effective field theory computation of the MSSM Higgs mass, improving the existing ones by including extra threshold corrections. We show that, with this approach, the theoretical uncertainty is within 1 GeV in most of the relevant parameter space. We confirm the smaller value of the Higgs mass found in the EFT computations, which implies a slightly heavier SUSY scale. We study the large tan β region, finding that sbottom thresholds might relax the upper bound on the scale of SUSY. We present SusyHD, a fast computer code that computes the Higgs mass and its uncertainty for any SUSY scale, from the TeV to the Planck scale, even in Split SUSY, both in the D R ¯ and in the on-shell schemes. Finally, we apply our results to derive bounds on some well motivated SUSY models, in particular we show how the value of the Higgs mass allows to determine the complete spectrum in minimal gauge mediation
de-Sitter vacua via consistent D-terms
We introduce a new mechanism for producing locally stable de-Sitter or
Minkowski vacua, with spontaneously broken N=1 supersymmetry and no massless
scalars, applicable to superstring and M-theory compactifications with fluxes.
We illustrate the mechanism with a simple N=1 supergravity model that provides
parametric control on the sign and the size of the vacuum energy. The crucial
ingredient is a gauged U(1) that involves both an axionic shift and an
R-symmetry, and severely constrains the F- and D-term contributions to the
potential.Comment: 4 pages, 1 figure, v3: published versio
Improved hot dark matter bound on the QCD axion
We strengthen the cosmological bound on the axion mass, by solving the
momentum-dependent Boltzmann equations for axion-pion scatterings and by using
a phenomenological production rate derived from pion-pion scattering data,
overcoming the breakdown of chiral perturbation theory. Using present
cosmological datasets we obtain . To further improve
the bound and exploit the reach of upcoming cosmological surveys, reliable
non-perturbative calculations above the QCD crossover are needed.Comment: 6+8 pages, 7 figure
More axion stars from strings
We show that if dark matter consists of QCD axions in the post-inflationary scenario more than ten percent of it efficiently collapses into Bose stars at matter-radiation equality. Such a result is mostly independent of the present uncertainties on the axion mass. This large population of solitons, with asteroid masses and Earth-Moon distance sizes, might plausibly survive until today, with potentially interesting implications for phenomenology and experimental searches
Chiral Corrections to the Hyperon Vector Form Factors
We present the complete calculation of the SU(3)-breaking corrections to the
hyperon vector form factors up to O(p^4) in the Heavy Baryon Chiral
Perturbation Theory. Because of the Ademollo-Gatto theorem, at this order the
results do not depend on unknown low energy constants and allow to test the
convergence of the chiral expansion. We complete and correct previous
calculations and find that O(p^3) and O(1/M_0) corrections are important. We
also study the inclusion of the decuplet degrees of freedom, showing that in
this case the perturbative expansion is jeopardized. These results raise doubts
on the reliability of the chiral expansion for hyperons.Comment: 20 pages, 4 figures, v2: published versio
- …