13,287 research outputs found
Natural Inflation from 5D SUGRA and Low Reheat Temperature
Motivated by recent cosmological observations of a possibly unsuppressed
primordial tensor component of inflationary perturbations, we reanalyse in
detail the 5D conformal SUGRA originated natural inflation model of Ref. [1].
The model is a supersymmetric variant of 5D extra natural inflation, also based
on a shift symmetry, and leads to the potential of natural inflation. Coupling
the bulk fields generating the inflaton potential via a gauge coupling to the
inflaton with brane SM states we necessarily obtain a very slow gauge inflaton
decay rate and a very low reheating temperature ~GeV. Analysis of the required number of e-foldings (from the CMB
observations) leads to values of in the lower range of present Planck
2015 results. Some related theoretical issues of the construction, along with
phenomenological and cosmological implications, are also discussed.Comment: Analysis and discussions updated in light of recent Planck and joint
analysis of BICEP2/Keck and Planck result
The MSSM from Scherk-Schwarz Supersymmetry Breaking
We present a five-dimensional model compactified on an interval where
supersymmetry is broken by the Scherk-Schwarz mechanism. The gauge sector
propagates in the bulk, two Higgs hypermultiplets are quasilocalized, and quark
and lepton multiplets localized, in one of the boundaries. The effective
four-dimensional theory is the MSSM with very heavy gauginos, heavy squarks and
light sleptons and Higgsinos. The soft tree-level squared masses of the Higgs
sector can be negative and they can (partially) cancel the positive one-loop
contributions from the gauge sector. Electroweak symmetry breaking can then
comfortably be triggered by two-loop radiative corrections from the top-stop
sector. The fine tuning required to obtain the electroweak scale is found to be
much smaller than in the MSSM, with essentially no fine-tuning for few TeV
gaugino masses. All bounds from direct Higgs searches at LEP and from
electroweak precision observables can be satisfied. The lightest supersymmetric
particle is a (Higgsino-like) neutralino that can accomodate the abundance of
Dark Matter consistently with recent WMAP observations.Comment: 23 pages, 3 figure
Radioactive ion beams for solid state research
Radioactive isotopes are widely used in many research fields. In some applications they are used as tracers after diffusion or after activation in the material itself through nuclear reactions. For research in solid state physics, the ion implantation technique is the most flexible and convenient method to introduce the radioactive isotopes in the materials to be studied, since it allows the control of the ion dose, the implantation depth and the isotopic purity. The on-line coupling of isotope separators to particle accelerators, as is the case of the ISOLDE facility at CERN, allows the obtention of a wide range of high purity short lived isotopes. Currently, the most stringent limitation for some applications is the low acceleration energy of 60 keV of the ISOLDE beam. In this communication a short review of the current applications of the radioactive beams for research in solid state physics at ISOLDE is done. The development of a post-accelerator facility for MeV radioactive ions is introduced and the advantages of energetic radioactive beams are discussed
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