7,392 research outputs found
Pacific Ocean Forcing and Atmospheric Variability are the Dominant Causes of Spatially Widespread Droughts in the Contiguous United States
The contributions of oceanic and atmospheric variability to spatially widespread summer droughts in the contiguous United States (hereafter, pan-CONUS droughts) are investigated using 16-member ensembles of the Community Climate Model version 3 (CCM3) forced with observed sea surface temperatures (SSTs) from 1856 to 2012. The employed SST forcing fields are either (i) global or restricted to the (ii) tropical Pacific or (iii) tropical Atlantic to isolate the impacts of these two ocean regions on pan-CONUS droughts. Model results show that SST forcing of pan-CONUS droughts originates almost entirely from the tropical Pacific because of atmospheric highs from the northern Pacific to eastern North America established by La Nia conditions, with little contribution from the tropical Atlantic. Notably, in all three model configurations, internal atmospheric variability influences pan-CONUS drought occurrence by as much or more than the ocean forcing and can alone cause pan-CONUS droughts by establishing a dominant high centered over the US montane West. Similar results are found for the Community Atmosphere Model version 5 (CAM5). Model results are compared to the observational record, which supports model-inferred contributions to pan-CONUS droughts from La Nias and internal atmospheric variability. While there may be an additional association with warm Atlantic SSTs in the observational record, this association is ambiguous due to the limited number of observed pan-CONUS. The ambiguity thus opens the possibility that the observational results are limited by sampling over the 20th-century and not at odds with the suggested dominance of Pacific Ocean forcing in the model ensembles
Quantum order by disorder in frustrated diamond lattice antiferromagnets
We present a quantum theory of frustrated diamond lattice antiferromagnets.
Considering quantum fluctuations as the predominant mechanism relieving spin
frustration, we find a rich phase diagram comprising of six phases with
coplanar spiral ordering in addition to the N\'eel phase. By computing the
specific heat of these ordered phases, we obtain a remarkable agreement between
-spiral ordering and the experimental specific heat data for the
diamond lattice spinel compounds MnScS, CoO and CoRhO,
i.e. specific heat data is a strong evidence for -spiral ordering in
all of these materials. This prediction can be tested in future neutron
scattering experiments on CoO and CoRhO, and is consistent with
existing neutron scattering data on MnScS. Based on this agreement we
infer a monotonically increasing relationship between frustration and the
strength of quantum fluctuations.Comment: 4 pages, 2 figures, version published in PR
Higgs Phenomenology with CPsuperH
The MSSM contains CP-violating phases that may have important observable
effects in Higgs physics. We review recent highlights in Higgs phenomenology
obtained with the code CPsuperH, a useful tool for studies of the production,
mixing and decay of a coupled system of the neutral Higgs bosons at future high
energy colliders such as the LHC, ILC (LC), and a muon collider (MC).
CPsuperH implements the constraints from upper limits on electric dipole
moments, and may be extended to include other related low-energy observables,
such as b -> s \gamma and B -> K l l, and to compute the relic abundance of the
lightest neutralino.Comment: 20 pages, LaTeX, 7 figures, invited article by Modern Physics Letters
A (review section
Hybridization-driven gap in U3Bi4Ni3: a 209Bi NMR/NQR study
We report 209Bi NMR and NQR measurements on a single crystal of the Kondo
insulator U3Bi4Ni3. The 209Bi nuclear spin-lattice relaxation rate ()
shows activated behavior and is well-fit by a spin gap of 220 K. The 209Bi
Knight shift (K) exhibits a strong temperature dependence arising from 5f
electrons, in which K is negative at high temperatures and increases as the
temperature is lowered. Below 50 K, K shows a broad maximum and decreases
slightly upon further cooling. Our data provide insight into the evolution of
the hyperfine fields in a fully gapped Kondo insulator based on 5f electron
hybridization.Comment: 4 pages, 4 figures, submitted to Phys. Rev.
Uncovering the Hidden Order in URu2Si2 by Impurity Doping
We report the use of impurities to probe the hidden order parameter of the
strongly correlated metal URu_2Si_2 below the transition temperature T_0 ~ 17.5
K. The nature of this order parameter has eluded researchers for more than two
decades, but is accompanied by the development of a partial gap in the single
particle density of states that can be detected through measurements of the
electronic specific heat and nuclear spin-lattice relaxation rate. We find that
impurities in the hidden order phase give rise to local patches of
antiferromagnetism. An analysis of the coupling between the antiferromagnetism
and the hidden order reveals that the former is not a competing order parameter
but rather a parasitic effect of the latter.Comment: 4 pages, 4 figure
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