698 research outputs found
Grand Unification, Axion, and Inflation in Intermediate Scale Supersymmetry
A class of supersymmetric grand unified theories is introduced that has a
single scale below the cutoff, that of the supersymmetry breaking masses
. For a wide range of the dimensionless parameters, agreement with
the observed mass of the Higgs boson determines , yielding Intermediate Scale Supersymmetry. We show that within this
framework it is possible for seesaw neutrino masses, axions, and inflation to
be described by the scale , offering the possibility of a unified
origin of disparate phenomena. Neutrino masses allowing for thermal
leptogenesis can be obtained, and the axion decay constant lies naturally in
the range , consistent with a recent
observational suggestion of high scale inflation. A minimal model is
presented that illustrates these features. In this model, the only states at
the grand unified scale are those of the heavy gauge supermultiplet. The grand
unified partners of the Higgs doublets have a mass of order ,
leading to the dominant proton decay mode , which
may be probed in upcoming experiments. Dark matter may be winos, with mass
environmentally selected to the TeV scale, and/or axions. Gauge coupling
unification is found to be successful, especially if the wino is at the TeV
scale.Comment: 27 pages, 7 figures; minor corrections, references and discussion
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Opacity of fluffy dust aggregates
Context. Dust grains coagulate to form dust aggregates in protoplanetary
disks. Their porosity can be extremely high in the disks. Although disk
emission may come from fluffy dust aggregates, the emission has been modeled
with compact grains. Aims. We aim to reveal the mass opacity of fluffy
aggregates from infrared to millimeter wavelengths with the filling factor
ranging from 1 down to . Methods. We use Mie calculations with an
effective medium theory. The monomers are assumed to be 0.1 sized
grains, which is much shorter than the wavelengths that we focus on. Results.
We find that the absorption mass opacity of fluffy aggregates are characterized
by the product , where is the dust radius and is the filling
factor, except for the interference structure. The scattering mass opacity is
also characterized by at short wavelengths while it is higher in more
fluffy aggregates at long wavelengths. We also derive the analytic formula of
the mass opacity and find that it reproduces the Mie calculations. We also
calculate the expected difference of the emission between compact and fluffy
aggregates in protoplanetary disks with a simple dust growth and drift model.
We find that compact grains and fluffy aggregates can be distinguished by the
radial distribution of the opacity index . The previous observation of
the radial distribution of is consistent with the fluffy case, but more
observations are required to distinguish between fluffy or compact. In
addition, we find that the scattered light would be another way to distinguish
between compact grains and fluffy aggregates.Comment: 16 pages, 17 figures, published in A&A, 568, A4
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