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An upper limit on the stochastic gravitational-wave background of cosmological origin

# An upper limit on the stochastic gravitational-wave background of cosmological origin,Nature,B. P. Abbott,R. Abbott,F. Acernese,R. Adhikari,P. Ajith,B

An upper limit on the stochastic gravitational-wave background of cosmological origin
B. P. Abbott, R. Abbott, F. Acernese, R. Adhikari, P. Ajith, B. Allen, G. Allen, M. Alshourbagy, R. S. Amin, S. B. Anderson, W. G. Anderson, F. Antonuccihttp://academic.research.microsoft.com/io.ashx?type=5&id=6924728&selfId1=0&selfId2=0&maxNumber=12&query=
A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations(1). Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory(2) (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be $<6.9\times10^{-6}$ at 95\% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter(3), as well as cosmic (super) string models with relatively small string tension(4) that are favoured in some string theory models(5). This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis(1,6) and cosmic microwave background(7) at 100Hz.
Journal: Nature , vol. 460, 2009
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## Citation Context (1)

• ...Quite interestingly, LIGO and Virgo have been able to set astrophysically relevant limits on the ellipticity of the Crab pulsar [3], and also to the neutron star in the supernova remnant Cassiopea A [2]...
• ...LIGO and Virgo detectors have achieved sensitivities such that they can start excluding regions of the parameter space of the expected signals and constrain the equation of state of the Universe during the dark age [19] in a physically significant way [7, 8]...

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