472 research outputs found
Report of the panel on earth structure and dynamics, section 6
The panel identified problems related to the dynamics of the core and mantle that should be addressed by NASA programs. They include investigating the geodynamo based on observations of the Earth's magnetic field, determining the rheology of the mantle from geodetic observations of post-glacial vertical motions and changes in the gravity field, and determining the coupling between plate motions and mantle flow from geodetic observations of plate deformation. Also emphasized is the importance of support for interdisciplinary research to combine various data sets with models which couple rheology, structure and dynamics
Changing patterns in electroweak precision with new color-charged states: Oblique corrections and the boson mass
The recent measurement by the CDF Collaboration of the boson mass is in
significant tension with the Standard Model expectation, showing a discrepancy
of seven standard deviations. A larger value of affects the global
electroweak fit, particularly the best-fit values of the Peskin-Takeuchi
parameters , (and perhaps ) that measure oblique corrections from new
physics. To meet this challenge, we propose some simple models capable of
generating non-negative and , the latter of which faces the greatest
upward pressure from the CDF measurement in scenarios with . Our models
feature weak multiplets of scalars charged under , which cannot attain nonzero vacuum expectation values
but nevertheless produce e.g. given some other mechanism to split
the electrically charged and neutral scalars. We compute the oblique
corrections in these models and identify ample parameter space supporting the
CDF value of .Comment: 27 pages, 4 figure
An increase in under hydrostatic pressure in the superconducting doped topological insulator NbBiSe
We report an unexpected positive hydrostatic pressure derivative of the
superconducting transition temperature in the doped topological insulator \NBS
via SQUID magnetometry in pressures up to 0.6 GPa. This result is contrary
to reports on the homologues \CBS and \SBS where smooth suppression of is
observed. Our results are consistent with recent Ginzburg-Landau theory
predictions of a pressure-induced enhancement of in the nematic
multicomponent state proposed to explain observations of rotational
symmetry breaking in doped BiSe superconductors.Comment: 5 pages, 5 figure
Anomalous Magnetic Ordering in PrBa₂Cu₄O₈ and CmBa₂Cu₃O₇
A review of temperature-dependent magnetization data for nonsuperconducting PrBa2Cu4O8 and CmBa2Cu3O7 suggests that the failure of each to superconduct is related to the presence of Pr and Cm on their respective Ba sites. This defect is manifested, in each case, by short c-axis lattice parameters and anomalous high-temperature magnetic ordering which has been incorrectly attributed to ordering of the entire magnetic sublattice. Instead, it is shown that the anomalous high-temperature ordering as seen in the magnetization data is consistent with the ordering of magnetic ions substituted on the Ba site
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