938 research outputs found
Quantum systems in weak gravitational fields
Fully covariant wave equations predict the existence of a class of
inertial-gravitational effects that can be tested experimentally. In these
equations inertia and gravity appear as external classical fields, but, by
conforming to general relativity, provide very valuable information on how
Einstein's views carry through in the world of the quantum.Comment: 22 pages. To be published in Proceedings of the 17th Course of the
International School of Cosmology and Gravitation "Advances in the interplay
between quantum and gravity physics" edited by V. De Sabbata and A.
Zheltukhin, Kluwer Academic Publishers, Dordrech
Complex circular subsidence structures in tephra deposited on large blocks of ice: VarĂ°a tuff cone, ĂrĂŠfajökull, Iceland
Several broadly circular structures up to 16 m in diameter, into which higher strata have sagged and locally collapsed, are present in a tephra outcrop on southwest ĂrĂŠfajökull, southern Iceland. The tephra was sourced in a nearby basaltic tuff cone at VarĂ°a. The structures have not previously been described in tuff cones, and they probably formed by the melting out of large buried blocks of ice emplaced during a preceding jökulhlaup that may have been triggered by a subglacial eruption within the ĂrĂŠfajökull ice cap. They are named ice-melt subsidence structures, and they are analogous to kettle holes that are commonly found in proglacial sandurs and some lahars sourced in ice-clad volcanoes. The internal structure is better exposed in the VarĂ°a examples because of an absence of fluvial infilling and reworking, and erosion of the outcrop to reveal the deeper geometry. The ice-melt subsidence structures at VarĂ°a are a proxy for buried ice. They are the only known evidence for a subglacial eruption and associated jökulhlaup that created the ice blocks. The recognition of such structures elsewhere will be useful in reconstructing more complete regional volcanic histories as well as for identifying ice-proximal settings during palaeoenvironmental investigations
Sensitive Search for a Permanent Muon Electric Dipole Moment
We are proposing a new method to carry out a dedicated search for a permanent
electric dipole moment (EDM) of the muon with a sensitivity at a level of
10^{-24} e cm. The experimental design exploits the strong motional electric
field sensed by relativistic particles in a magnetic storage ring. As a key
feature, a novel technique has been invented in which the g-2 precession is
compensated with radial electric field. This technique will benefit greatly
when the intense muon sources advocated by the developers of the muon storage
rings and the muon colliders become available.Comment: 16 pages, 3 figures. Submitted for publication in Proceedings of the
International Workshop on High Intensity Muon Sources (HIMUS99), KEK, Japan,
December 1-4 199
Quantum physics in inertial and gravitational fields
Covariant generalizations of well-known wave equations predict the existence
of inertial-gravitational effects for a variety of quantum systems that range
from Bose-Einstein condensates to particles in accelerators. Additional effects
arise in models that incorporate Born reciprocity principle and the notion of a
maximal acceleration. Some specific examples are discussed in detail.Comment: 25 pages,1 figure,to appear in "Relativity in Rotating Frame
Methane in the atmosphere of the transiting hot Neptune GJ436b?
We present an analysis of seven primary transit observations of the hot
Neptune GJ436b at 3.6, 4.5 and m obtained with the Infrared Array Camera
(IRAC) on the Spitzer Space Telescope. After correcting for systematic effects,
we fitted the light curves using the Markov Chain Monte Carlo technique.
Combining these new data with the EPOXI, HST and ground-based and
published observations, the range m can be covered. Due to
the low level of activity of GJ436, the effect of starspots on the combination
of transits at different epochs is negligible at the accuracy of the dataset.
Representative climate models were calculated by using a three-dimensional,
pseudo-spectral general circulation model with idealised thermal forcing.
Simulated transit spectra of GJ436b were generated using line-by-line radiative
transfer models including the opacities of the molecular species expected to be
present in such a planetary atmosphere. A new, ab-initio calculated, linelist
for hot ammonia has been used for the first time. The photometric data observed
at multiple wavelengths can be interpreted with methane being the dominant
absorption after molecular hydrogen, possibly with minor contributions from
ammonia, water and other molecules. No clear evidence of carbon monoxide and
dioxide is found from transit photometry. We discuss this result in the light
of a recent paper where photochemical disequilibrium is hypothesised to
interpret secondary transit photometric data. We show that the emission
photometric data are not incompatible with the presence of abundant methane,
but further spectroscopic data are desirable to confirm this scenario.Comment: 19 pages, 10 figures, 1 table, Astrophysical Journal in pres
Parton energy loss limits and shadowing in Drell-Yan dimuon production
A precise measurement of the ratios of the Drell-Yan cross section per
nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is
reported. The behavior of the Drell-Yan ratios at small target parton momentum
fraction is well described by an existing fit to the shadowing observed in
deep-inelastic scattering. The cross section ratios as a function of the
incident parton momentum fraction set tight limits on the energy loss of quarks
passing through a cold nucleus
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Giving something back? Sentiments of privilege and social responsibility among elite graduates from Britain and France
This article explores the complex relationship between transnational elites and civil society through examining the contrasting orientations of two cohorts of âelite graduatesâ from Paris and Oxford. Both cohorts believe their privileged status has been earned through hard work and ability. But they are also aware that they have benefited from advantages not available to all. Perhaps because of this, they express the need to âgive something backâ. However, the means through which they seek to discharge their social responsibilities are very different. While the Oxford graduates seek to âgive something backâ through volunteering and third sector engagement, the Paris graduates will âgive something backâ through public service. The article discusses how the contrasting relationship between the state, civil society and the education system in these two countries may shape dispositions, and speculates on the extent to which these elite recruitsâ commitment to âgive something backâ will make a difference
Improved Measurement of the Positive Muon Anomalous Magnetic Moment
A new measurement of the positive muon's anomalous magnetic moment has been
made at the Brookhaven Alternating Gradient Synchrotron using the direct
injection of polarized muons into the superferric storage ring. The angular
frequency difference omega_{a} between the angular spin precession frequency
omega_{s} and the angular orbital frequency omega_{c} is measured as well as
the free proton NMR frequency omega_{p}. These determine
R = omega_{a} / omega_{p} = 3.707~201(19) times 10^{-3}. With mu_{mu} /
mu_{p} = 3.183~345~39(10) this gives a_{mu^+} = 11~659~191(59) times 10^{-10}
(pm 5 ppm), in good agreement with the previous CERN and BNL measurements for
mu^+ and mu^-, and with the standard model prediction.Comment: 4 pages, 4 figures. accepted for publication in Phys. Rev. D62 Rapid
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