15,943 research outputs found
Design of a speed meter interferometer proof-of-principle experiment
The second generation of large scale interferometric gravitational wave
detectors will be limited by quantum noise over a wide frequency range in their
detection band. Further sensitivity improvements for future upgrades or new
detectors beyond the second generation motivate the development of measurement
schemes to mitigate the impact of quantum noise in these instruments. Two
strands of development are being pursued to reach this goal, focusing both on
modifications of the well-established Michelson detector configuration and
development of different detector topologies. In this paper, we present the
design of the world's first Sagnac speed meter interferometer which is
currently being constructed at the University of Glasgow. With this
proof-of-principle experiment we aim to demonstrate the theoretically predicted
lower quantum noise in a Sagnac interferometer compared to an equivalent
Michelson interferometer, to qualify Sagnac speed meters for further research
towards an implementation in a future generation large scale gravitational wave
detector, such as the planned Einstein Telescope observatory.Comment: Revised version: 16 pages, 6 figure
3-D multiobservable probabilistic inversion for the compositional and thermal structure of the lithosphere and upper mantle: III. Thermochemical tomography in the Western-Central U.S.
Acknowledgments We are indebted to F. Darbyshire and J. von Hunen for useful comments on earlier versions of this work. This manuscript benefited from thorough and constructive reviews by W. Levandowski and an anonymous reviewer. We also thank J. Connolly, M. Sambridge, B. Kennett, S. Lebedev, B. Shan, U. Faul, and M. Qashqai for insightful discussions about, and contributions to, some of the concepts presented in this paper. The work of J.C.A. has been supported by two Australian Research Council Discovery grants (DP120102372 and DP110104145). Seismic data are from the IRIS DMS. D.L.S. acknowledges support from NSF grant EAR-135866. This is contribution 848 from the ARC Centre of Excellence for Core to Crust Fluid Systems (http://www.ccfs.mq.edu.au) and 1106 in the GEMOC Key Centre (http://www.gemoc.mq.edu.au).Peer reviewedPublisher PD
Verifying asteroseismically determined parameters of Kepler stars using hipparcos parallaxes: self-consistent stellar properties and distances
Accurately determining the properties of stars is of prime importance for
characterizing stellar populations in our Galaxy. The field of asteroseismology
has been thought to be particularly successful in such an endeavor for stars in
different evolutionary stages. However, to fully exploit its potential, robust
methods for estimating stellar parameters are required and independent
verification of the results is mandatory. With this purpose, we present a new
technique to obtain stellar properties by coupling asteroseismic analysis with
the InfraRed Flux Method. By using two global seismic observables and
multi-band photometry, the technique allows us to obtain masses, radii,
effective temperatures, bolometric fluxes, and hence distances for field stars
in a self-consistent manner. We apply our method to 22 solar-like oscillators
in the Kepler short-cadence sample, that have accurate Hipparcos parallaxes.
Our distance determinations agree to better than 5%, while measurements of
spectroscopic effective temperatures and interferometric radii also validate
our results. We briefly discuss the potential of our technique for stellar
population analysis and models of Galactic Chemical Evolution.Comment: 28 pages, 5 figures, ApJ, accepte
Asteroseismic diagrams for solar-type stars
We explore the feasibility of applying the Christensen-Dalsgaard diagram to
real asteroseismic data and provide quantitative measures of the uncertainty
associated with the results. We also propose a new kind of seismic diagram,
based on the determination of the locations of sharp acoustic features inside a
star. We show that by combining the information about the position of the base
of the convective envelope or the HeII ionisation zone with a measure of the
average large separation, it is possible to constrain the unknown chemical
composition or the various parameters characterising the physical processes in
the stellar interior. We demonstrate the application of this technique to the
analysis of mock data for a CoRoT target star.Comment: Accepted for publication in A&
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Imaging of a fluid injection process using geophysical data - A didactic example
In many subsurface industrial applications, fluids are injected into or withdrawn from a geologic formation. It is of practical interest to quantify precisely where, when, and by how much the injected fluid alters the state of the subsurface. Routine geophysical monitoring of such processes attempts to image the way that geophysical properties, such as seismic velocities or electrical conductivity, change through time and space and to then make qualitative inferences as to where the injected fluid has migrated. The more rigorous formulation of the time-lapse geophysical inverse problem forecasts how the subsurface evolves during the course of a fluid-injection application. Using time-lapse geophysical signals as the data to be matched, the model unknowns to be estimated are the multiphysics forward-modeling parameters controlling the fluid-injection process. Properly reproducing the geophysical signature of the flow process, subsequent simulations can predict the fluid migration and alteration in the subsurface. The dynamic nature of fluid-injection processes renders imaging problems more complex than conventional geophysical imaging for static targets. This work intents to clarify the related hydrogeophysical parameter estimation concepts
Seismic anisotropy of Precambrian lithosphere : Insights from Rayleigh wave tomography of the eastern Superior Craton
The seismic data used in this study are freely available from the CNDC (Canadian National Data Centre for Earthquake Seismology and Nuclear Explosion Monitoring) and IRIS DMC (Data Management Center) via their data request tools. The Leverhulme Trust (grant RPG-2013-332) and National Science Foundation are acknowledged for financial support. L.P. is supported by Janet Watson Imperial College Department Scholarship and the Romanian Government Research Grant NUCLEU. F.D. is supported by NSERC through the Discovery Grants and Canada Research Chairs program. We also thank two anonymous reviewers and the Associate Editor for insightful comments that helped improve the manuscript.Peer reviewedPublisher PD
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