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Published August 20, 2009 | Accepted Version + Supplemental Material
Journal Article Open

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


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 10^(-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 100 Hz.

Additional Information

© 2009 Macmillan Publishers Limited. Received 20 May; accepted 30 June 2009. We acknowledge the support of the United States National Science Foundation for the construction and operation of the LIGO Laboratory, the Science and Technology Facilities Council of the United Kingdom, the Max Planck Society, and the State of Niedersachsen/Germany for support of the construction and operation of the GEO600 detector, and the Italian Istituto Nazionale di Fisica Nucleare and the French Centre National de la Recherche Scientifique for the construction and operation of the Virgo detector. We also acknowledge the support of the research by these agencies and by the Australian Research Council, the Council of Scientific and Industrial Research of India, the Istituto Nazionale di Fisica Nucleare of Italy, the Spanish Ministerio de Educacion y Ciencia, the Conselleria d'Economia Hisenda i Innovacio of the Govern de les Illes Balears, the Royal Society, the Scottish Funding Council, the Scottish Universities Physics Alliance, The National Aeronautics and Space Administration, the Carnegie Trust, the Leverhulme Trust, the David and Lucile Packard Foundation, the Research Corporation, and the Alfred P. Sloan Foundation.

Attached Files

Accepted Version - 0910.5772.pdf

Supplemental Material - nature08278-s1.pdf


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