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An upper limit in the stochastic gravitational-wave background of cosmological origin (LIGO)

Date

2009

Authors

McClelland, David
Gray, Malcolm
Lam, Ping Koy
McKenzie, Kirk
Mow-Lowry, C
Mullavey, Adam
Satterthwaite, Matthew
Scott, Susan M
Slagmolen, Bram
Wette, Karl

Journal Title

Journal ISSN

Volume Title

Publisher

Macmillan Publishers Ltd

Abstract

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. 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 (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 × 10-6 at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter, as well as cosmic (super)string models with relatively small string tension that are favoured in some string theory models. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis and cosmic microwave background at 100 Hz.

Description

Keywords

Keywords: astrophysics; cosmology; equation of state; gravity wave; interferometer; numerical model; stochasticity; article; cosmological phenomena; cosmos; density; energy; evolution; frequency analysis; frequency modulation; gravity; interferometer; microwave rad

Citation

Source

Nature

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.1038/nature08278

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