37,266 research outputs found
Letter from T. D. Graham to the Elders of the Church of Christ in Gainesville
Postcard from T. D. Graham to the Elders of the Church of Christ at Gainesville, Florida. The handwritten postcard is dated 17 November 1913. There is a transcript of the correspondence in the item PDF
Sea state and rain: a second take on dual-frequency altimetry
TOPEX and Jason were the first two dual-frequency altimeters in space, with both operating at Ku- and C-band. Each thus gives two measurements of the normalized backscatter, sigma0, (from which wind speed is calculated) and two estimates of wave height. Departures from a well-defined relationship between the Ku- and C-band sigma0 values give an indication of rain.This paper investigates differences between the two instruments using data from Jason's verification phase. Jason's Ku-band estimates of wave height are ~1.8% less than TOPEX's, whereas its sigma0 values are higher. When these effects have been removed the root mean square (r.m.s.) mismatch between TOPEX and Jason's Ku-band observations is close to that for TOPEX's observations at its two frequencies, and the changes in sigma0 with varying wave height conditions are the same for the two altimeters. Rain flagging and quantitative estimates of rain rate are both based on the atmospheric attenuation derived from the sigma0 measurements at the two frequencies. The attenuation estimates of TOPEX and Jason agree very well, and a threshold of -0.5 dB is effective at removing the majority of spurious data records from the Jason GDRs. In the high sigma0 regime, anomalous data can be cause by processes other than rain. Consequently, for these low wind conditions, neither can reliable rain detection be based on altimetry alone, nor can a generic rain flag be expected to remove all suspect data
Supersoft Supersymmetry is Super-Safe
We show that supersymmetric models with a large Dirac gluino mass can evade
much of the jets plus missing energy searches at LHC. Dirac gaugino masses
arise from "supersoft" operators that lead to finite one-loop suppressed
contributions to the scalar masses. A little hierarchy between the Dirac gluino
mass 5 - 10 times heavier than the squark masses is automatic and technically
natural, in stark contrast to supersymmetric models with Majorana gaugino
masses. At the LHC, colored sparticle production is suppressed not only by the
absence of gluino pair (or associated) production, but also because several of
the largest squark pair production channels are suppressed or absent. We recast
the null results from the present jets plus missing energy searches at LHC for
supersymmetry onto a supersoft supersymmetric simplified model (SSSM). Assuming
a massless LSP, we find the strongest bounds are: 748 GeV from a 2j + MET
search at ATLAS (4.7 fb^{-1}), and 684 GeV from a combined jets plus missing
energy search using at CMS (1.1 fb^{-1}). In the absence of a future
observation, we estimate the bounds on the squark masses to improve only
modestly with increased luminosity. We also briefly consider the further
weakening in the bounds as the LSP mass is increased.Comment: 13 pages, 8 figure
The importance of planetary rotation period for ocean heat transport
The climate, and hence potential habitability, of a planet crucially depends on how its atmospheric and oceanic circulation transports heat from warmer to cooler regions. However, previous studies of planetary climate have concentrated on modelling the dynamics of their atmospheres whilst dramatically simplifying the treatment of the oceans, which neglects or misrepresents the effect of the ocean in the total heat transport. Even the majority of studies with a dynamic ocean have used a simple so-called aquaplanet having no continental barriers, which is a configuration which dramatically changes the oceanic dynamics. Here the significance of the response of poleward ocean heat transport to planetary rotation period is shown with a simple meridional barrier – the simplest representation of any continental configuration. The poleward ocean heat transport increases significantly as the planetary rotation period is increased. The peak heat transport more than doubles when the rotation period is increased by a factor of ten. There are also significant changes to ocean temperature at depth, with implications for the carbon cycle. There is strong agreement between the model results and a scale analysis of the governing equations. This result highlights the importance of both planetary rotation period and the ocean circulation when considering planetary habitability
Hyperentanglement-enabled Direct Characterization of Quantum Dynamics
We use hyperentangled photons to experimentally implement an
entanglement-assisted quantum process tomography technique known as Direct
Characterization of Quantum Dynamics. Specifically, hyperentanglement-assisted
Bell-state analysis enabled us to characterize a variety of single-qubit
quantum processes using far fewer experimental configurations than are required
by Standard Quantum Process Tomography (SQPT). Furthermore, we demonstrate how
known errors in Bell-state measurement may be compensated for in the data
analysis. Using these techniques, we have obtained single-qubit process
fidelities as high as 98.2% but with one-third the number experimental
configurations required for SQPT. Extensions of these techniques to multi-qubit
quantum processes are discussed.Comment: This is part of a joint submission with an implementation with Ions:
"Experimental characterization of quantum dynamics through many-body
interactions" by Daniel Nigg, Julio T. Barreiro, Philipp Schindler, Masoud
Mohseni, Thomas Monz, Michael Chwalla, Markus Hennrich and Rainer Blat
Quantum states on supersymmetric minisuperspace with a cosmological constant
Spatially homogeneous models in quantum supergravity with a nonvanishing
cosmological constant are studied. A class of exact nontrivial solutions of the
supersymmetry and Lorentz constraints is obtained in terms of the Chern-Simons
action on the spatially homogeneous 3-manifold, both in Ashketar variables
where the solution is explicit up to reality conditions, and, more concretely,
in the tetrad-representation, where the solutions are given as integral
representations differing only by the contours of integration. In the limit of
a vanishing cosmological constant earlier exact solutions for Bianchi type IX
models in the tetrad-representation are recovered and additional asymmetric
solutions are found.Comment: 14 pages, late
Fermion Energies in the Background of a Cosmic String
We provide a thorough exposition, including technical and numerical details,
of previously published results on the quantum stabilization of cosmic strings.
Stabilization occurs through the coupling to a heavy fermion doublet in a
reduced version of the standard model. We combine the vacuum polarization
energy of fermion zero-point fluctuations and the binding energy of occupied
energy levels, which are of the same order in a semi-classical expansion.
Populating these bound states assigns a charge to the string. We show that
strings carrying fermion charge become stable if the electro-weak bosons are
coupled to a fermion that is less than twice as heavy as the top quark. The
vacuum remains stable in our model, because neutral strings are not
energetically favored. These findings suggests that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev
Third Space, Social Media and Everyday Political Talk
Theoretical and empirical research into online politics to date has primarily focused on what might be called formal politics or on how activists and social movements utilize social media to pursue their goals. However, in this chapter, we argue that there is much to be gained by investigating how political talk and engagement emerges in everyday, online, lifestyle communities: i.e. third spaces. Such spaces are not intended for political purposes, but rather – during the course of everyday talk – become political through the connections people make between their everyday lives and the political/social issues of the day. In this chapter, we develop a theoretically informed argument for research that focuses on everyday informal political talk in online third spaces
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