1,452 research outputs found
Entangled spinning particles in charged and rotating black holes
Spin precession for an EPR pair of spin-1/2 particles in equatorial orbits
around a Kerr-Newman black hole is studied. Hovering observers are introduced
to ensure fixed reference frames in order to perform the Wigner rotation. These
observers also guarantee a reliable direction to compare spin states in
rotating black holes. The velocity of the particle due frame-dragging is
explicitly incorporated by addition of velocities with respect the hovering
observers and the corresponding spin precession angle is computed. The
spin-singlet state is observed to be mixed with the spin-triplet by dynamical
and gravity effects, thus it is found that a perfect anti-correlation of
entangled states for these observers is deteriorated. Finally, an analysis
concerning the different limit cases of parameters of spin precession including
the frame-dragging effects is carried out.Comment: 25+1 pages, 7 eps figures. Major changes were made through all the
manuscript. Clarifications regarding modifications were introduced through
the draft. Figures were changed and reduced in number. arXiv admin note: text
overlap with arXiv:quant-ph/030711
Understanding the evolution of native pinewoods in Scotland will benefit their future management and conservation
Scots pine (Pinus sylvestris L.) is a foundation species in Scottish highland forests and a national icon. Due to heavy exploitation, the current native pinewood coverage represents a small fraction of the postglacial maximum. To reverse this decline, various schemes have been initiated to promote planting of new and expansion of old pinewoods. This includes the designation of seed zones for control of the remaining genetic resources. The zoning was based mainly on biochemical similarity among pinewoods but, by definition, neutral molecular markers do not reflect local phenotypic adaptation. Environmental variation within Scotland is substantial and it is not yet clear to what extent this has shaped patterns of adaptive differentiation among Scottish populations. Systematic, rangewide common-environment trials can provide insights into the evolution of the native pinewoods, indicating how environment has influenced phenotypic variation and how variation is maintained. Careful design of such experiments can also provide data on the history and connectivity among populations, by molecular marker analysis. Together, phenotypic and molecular datasets from such trials can provide a robust basis for refining seed transfer guidelines for Scots pine in Scotland and should form the scientific basis for conservation action on this nationally important habitat
Evaluation of the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS)
This evaluation has been commissioned by the Independent Evaluation Arrangement (IEA) of CGIAR. Following consultation with the ISP and CCAFS management, the Evaluation addressed four key evaluation questions.
1) How well is strategic collaboration and integration both within and outside the CGIAR being achieved? 2) To what extent is CCAFS generating unique international public goods for agriculture, food security and climate change? 3) How well do the Flagship Projects link together and combine at output and outcome levels in the regions; and, to what extent are successes toward outcomes transferable from region to region? 4) How robust are the monitoring, evaluation and learning processes of the Program?
As its main approach, the Evaluation selected nine projects for case studies to address the evaluation criteria and questions at three levels: global Program level, Flagship level and Regional Program level. The methodology also included document review, field visits to all regions, interviews of over 150 stakeholders, survey of CCAFS researchers, identification of exemplary cases of CCAFS work with high impact potential using a triple loop learning analysis, bibliometric analysis and H-index analysis of senior researchers. An independent third-party review team contributed to the evaluation of quality of science by assessing a random sample of journal articles published by CCAFS
Opening up the Quantum Three-Box Problem with Undetectable Measurements
One of the most striking features of quantum mechanics is the profound effect
exerted by measurements alone. Sophisticated quantum control is now available
in several experimental systems, exposing discrepancies between quantum and
classical mechanics whenever measurement induces disturbance of the
interrogated system. In practice, such discrepancies may frequently be
explained as the back-action required by quantum mechanics adding quantum noise
to a classical signal. Here we implement the 'three-box' quantum game of
Aharonov and Vaidman in which quantum measurements add no detectable noise to a
classical signal, by utilising state-of-the-art control and measurement of the
nitrogen vacancy centre in diamond.
Quantum and classical mechanics then make contradictory predictions for the
same experimental procedure, however classical observers cannot invoke
measurement-induced disturbance to explain this discrepancy. We quantify the
residual disturbance of our measurements and obtain data that rule out any
classical model by > 7.8 standard deviations, allowing us for the first time to
exclude the property of macroscopic state-definiteness from our system. Our
experiment is then equivalent to a Kochen-Spekker test of quantum
non-contextuality that successfully addresses the measurement detectability
loophole
Towards a classification of entanglements of Galois representations attached to elliptic curves
Let be an elliptic curve, let be a
fixed algebraic closure of , and let
be the absolute
Galois group of . The action of on the adelic Tate
module of induces the adelic Galois representation
The goal of this paper is to explain how the image of can be smaller
than expected. To this end, we offer a group theoretic categorization of
different ways in which an entanglement between division fields can be
explained and prove several results on elliptic curves (and more generally,
principally polarized abelian varieties) over where the
entanglement occurs over an abelian extension.Comment: 33 pages; final versio
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