Title

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

Authors

B. P. Abbott, California Institute of Technology
R. Abbott, California Institute of Technology
F. Acernese, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
R. Adhikari, California Institute of Technology
P. Ajith, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
B. Allen, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
G. Allen, Stanford University
M. Alshourbagy, Istituto Nazionale di Fisica Nucleare, Sezione di Pisa
R. S. Amin, Louisiana State University
S. B. Anderson, California Institute of Technology
W. G. Anderson, University of Wisconsin-Milwaukee
F. Antonucci, Istituto Nazionale di Fisica Nucleare - INFN
S. Aoudia, Astrophysique Relativiste, Théories, Expériences, Metrologie, Instrumentation, Signaux
M. A. Arain, University of Florida
M. Araya, California Institute of Technology
H. Armandula, California Institute of Technology
P. Armor, University of Wisconsin-Milwaukee
K. G. Arun, Laboratoire de l'Accélérateur Linéaire
Y. Aso, California Institute of Technology
S. Aston, University of Birmingham
P. Astone, Istituto Nazionale di Fisica Nucleare - INFN
P. Aufmuth, Gottfried Wilhelm Leibniz Universität Hannover
C. Aulbert, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
S. Babak, Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
P. Baker, Montana State University
G. Ballardin, European Gravitational Observatory (EGO)
S. Ballmer, California Institute of Technology
C. Barker, LIGO Hanford
D. Barker, LIGO Hanford
F. Barone, Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
B. Barr, University of Glasgow
P. Barriga, The University of Western Australia
L. Barsotti, Massachusetts Institute of Technology

Document Type

Article

Publication Date

8-20-2009

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. © 2009 Macmillan Publishers Limited. All rights reserved.

Publication Source (Journal or Book title)

Nature

First Page

990

Last Page

994

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