8,942 research outputs found
Testing Split Supersymmetry with Inflation
Split supersymmetry (SUSY) -- in which SUSY is relevant to our universe but
largely inaccessible at current accelerators -- has become increasingly
plausible given the absence of new physics at the LHC, the success of gauge
coupling unification, and the observed Higgs mass. Indirect probes of split
SUSY such as electric dipole moments (EDMs) and flavor violation offer hope for
further evidence but are ultimately limited in their reach. Inflation offers an
alternate window into SUSY through the direct production of superpartners
during inflation. These particles are capable of leaving imprints in future
cosmological probes of primordial non-gaussianity. Given the recent
observations of BICEP2, the scale of inflation is likely high enough to probe
the full range of split SUSY scenarios and therefore offers a unique advantage
over low energy probes. The key observable for future experiments is
equilateral non-gaussianity, which will be probed by both cosmic microwave
background (CMB) and large scale structure (LSS) surveys. In the event of a
detection, we forecast our ability to find evidence for superpartners through
the scaling behavior in the squeezed limit of the bispectrum.Comment: 19 pages, 6 figure
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The Role of the Magnetorotational Instability in the Sun
We calculate growth rates for nonaxisymmetric instabilities including the
magnetorotational instability (MRI) throughout the Sun. We first derive a
dispersion relation for nonaxisymmetric instability including the effects of
shear, convective buoyancy, and three diffusivities (thermal conductivity,
resistivity, and viscosity). We then use a solar model evolved with the stellar
evolution code MESA and angular velocity profiles determined by Global
Oscillations Network Group (GONG) helioseismology to determine the unstable
modes present at each location in the Sun and the associated growth rates. The
overall instability has unstable modes throughout the convection zone and also
slightly below it at middle and high latitudes. It contains three classes of
modes: large-scale hydrodynamic convective modes, large-scale hydrodynamic
shear modes, and small-scale magnetohydrodynamic (MHD) shear modes, which may
be properly called MRI modes. While large-scale convective modes are the most
rapidly growing modes in most of the convective zone, MRI modes are important
in both stably stratified and convectively unstable locations near the
tachocline at colatitudes theta less than 53 degrees. Nonaxisymmetric MRI modes
grow faster than the corresponding axisymmetric modes; for some poloidal
magnetic fields, the nonaxisymmetric MRI growth rates are similar to the
angular rotation frequency Omega, while axisymmetric modes are stabilized. We
briefly discuss the saturation of the field produced by MRI modes, finding that
the implied field at the base of the convective zone in the Sun is comparable
to that derived based on dynamos active in the tachocline and that the
saturation of field resulting from the MRI may be of importance even in the
upper convection zone.Comment: 20 pages, 11 figure
Building a Better mSUGRA: WIMP Dark Matter Without Flavor Violation
The appearance of a natural dark matter candidate, the neutralino, is among
the principal successes of minimal supergravity (mSUGRA) and its descendents.
In lieu of a suitable ultraviolet completion, however, theories of
gravity-mediated supersymmetry breaking such as mSUGRA suffer from arbitrary
degrees of flavor violation. Though theories of gauge-mediated supersymmetry
breaking are free from such prohibitive flavor violation, they typically lack
natural neutralino dark matter candidates. Yet this conventional dichotomy
breaks down when the hidden sector is strongly coupled; in models of
gauge-mediated supersymmetry breaking, the neutralino may be the lightest
supersymmetric particle (LSP) if the fields of the hidden sector possess large
anomalous dimensions. In fact, general models of so-called "sequestered" gauge
mediation possess the full richness of neutralino dark matter found in mSUGRA
without corresponding flavor problems. Here we explore generalized models of
sequestered gauge mediation and the rich variety of neutralino dark matter they
exhibit.Comment: 26 pages, 7 figure
An Annotated Checklist of Wisconsin Mutillidae (Hymenoptera)
A survey of Wisconsin velvet ants (Hymenoptera: Mutillidae) conducted from literature searches, collection inventories, and two years of field work (2001-2002) yielded 28 species in three subfamilies. Of these, 23 species (representing 82% of the Wisconsin fauna and a 460% increase in the known species richness) are new state species records, having not previously been recorded in the published literature from the state. The known distributions of all Wisconsin species are reported by region and county, along with pertinent phenological, natural history, and other collection information, when known
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Bioaugmentation for Improved Recovery of Anaerobic Digesters After Toxicant Exposure
Bioaugmentation was investigated as a method to decrease the recovery period of anaerobic digesters exposed to a transient toxic event. Two sets of laboratory-scale digesters (SRT = 10 days, OLR = 2 g COD/L-day), started with inoculum from a digester stabilizing synthetic municipal wastewater solids (MW) and synthetic industrial wastewater (WW), respectively, were transiently exposed to the model toxicant, oxygen. Bioaugmented digesters received 1.2 g VSS/L-day of an H2-utilizing culture for which the archaeal community was analyzed. Soon after oxygen exposure, the bioaugmented digesters produced 25–60% more methane than non-bioaugmented controls (p \u3c 0.05). One set of digesters produced lingering high propionate concentrations, and bioaugmentation resulted in significantly shorter recovery periods. The second set of digesters did not display lingering propionate, and bioaugmented digesters recovered at the same time as non-bioaugmented controls. The difference in the effect of bioaugmentation on recovery may be due to differences between microbial communities of the digester inocula originally employed. In conclusion, bioaugmentation with an H2-utilizing culture is a potential tool to decrease the recovery period, decrease propionate concentration, and increase biogas production of some anaerobic digesters after a toxic event. Digesters already containing rapidly adaptable microbial communities may not benefit from bioaugmentation, whereas other digesters with poorly adaptable microbial communities may benefit greatly
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