Paper abstract bibtex

Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of ?_(GW)(f)=?_\ensuremath\alpha(f/f_(ref))_\ensuremath\alpha, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5?1726 Hz. In the frequency band of 41.5?169.25 Hz for a spectral index of \ensuremath\alpha=0, we constrain the energy density of the stochastic background to be ?_(GW)(f)\ensuremath<5.6$\times$10\^ (?6). For the 600?1000 Hz band, ?_(GW)(f)\ensuremath<0.14(f/900 Hz)\^ 3, a factor of 2.5 lower than the best previously reported upper limits. We find ?_(GW)(f)\ensuremath<1.8$\times$10\^ (?4) using a spectral index of zero for 170?600 Hz and ?_(GW)(f)\ensuremath<1.0(f/1300 Hz)\^ 3 for 1000?1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.

@article{caltechauthors53285, volume = {113}, number = {23}, month = {December}, author = {J. Aasi and B. P. Abbott and R. Abbott and M. R. Abernathy and R. X. Adhikari and R. Anderson and S. B. Anderson and K. Arai and M. C. Araya and L. Austin and J. C. Barayoga and B. C. Barish and G. Billingsley and E. Black and J. K. Blackburn and R. Bork and A. F. Brooks and C. Cepeda and R. Chakraborty and T. Chalermsongsak and D. C. Coyne and V. Dergachev and R. W. P. Drever and J. C. Driggers and P. Ehrens and T. Etzel and K. Gushwa and E. K. Gustafson and J. Harms and A. W. Heptonstall and K. A. Hodge and A. Ivanov and M. Jacobson and E. James and P. Kalmus and J. B. Kanner and W. Kells and P. J. King and V. Kondrashov and W. Z. Korth and D. B. Kozak and A. Lazzarini and J. Lewis and T. G. F. Li and K. Libbrecht and V. Litvine and M. Mageswaran and K. Mailand and E. Maros and D. Martynov and J. N. Marx and G. McIntyre and S. Meshkov and C. Osthelder and M. Pedraza and M. Phelps and L. R. Price and S. Privitera and E. Quintero and V. Raymond and N. A. Robertson and J. G. Rollins and V. Sannibale and A. Singer and L. Singer and M. Smith and R. J. E. Smith and N. D. Smith-Lefebvre and R. Taylor and M. P. Thirugnanasambandam and E. Thrane and C. I. Torrie and S. Vass and L. Wallace and A. J. Weinstein and R. Williams and H. Yamamoto and L. Zhang and J. Zweizig and Y. Chen and S. Gossan and H. Miao and P. Moesta and K. S. Thorne and M. Vallisneri and H. Yang and D. H. Reitze}, note = {{\copyright} 2014 American Physical Society. Received 7 July 2014; published 2 December 2014. The authors gratefully acknowledge the support of the U. S. 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. The authors also gratefully acknowledge the support of the research by these agencies and by the Australian Research Council, the International Science Linkages program of the Commonwealth of Australia, the Council of Scientific and Industrial Research of India, the Istituto Nazionale di Fisica Nucleare of Italy, the Spanish Ministerio de Econom{\'i}a y Competitividad, the Conselleria d?Economia Hisenda i Innovaci{\'o} of the Govern de les Illes Balears, the Foundation for Fundamental Research on Matter supported by the Netherlands Organisation for Scientific Research, the Polish Ministry of Science and Higher Education, the FOCUS Programme of Foundation for Polish Science, the Royal Society, the Scottish Funding Council, the Scottish Universities Physics Alliance, the National Aeronautics and Space Administration, the National Research Foundation of Korea, Industry Canada and the Province of Ontario through the Ministry of Economic Development and Innovation, the National Science and Engineering Research Council Canada, the Carnegie Trust, the Leverhulme Trust, the David and Lucile Packard Foundation, the Research Corporation, the OTKA of Hungary, the Science and Technologies Funding Council of the UK, the Lyon Institute of Origins (LIO), and the Alfred P. Sloan Foundation.}, title = {Improved Upper Limits on the Stochastic Gravitational-Wave Background from 2009?2010 LIGO and Virgo Data}, publisher = {American Physical Society}, year = {2014}, journal = {Physical Review Letters}, pages = {Art. No. 231101}, url = {http://resolver.caltech.edu/CaltechAUTHORS:20150107-131249161}, abstract = {Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of ?\_(GW)(f)=?\_{\ensuremath{\alpha}}(f/f\_(ref))\_{\ensuremath{\alpha}}, we place 95\% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5?1726 Hz. In the frequency band of 41.5?169.25 Hz for a spectral index of {\ensuremath{\alpha}}=0, we constrain the energy density of the stochastic background to be ?\_(GW)(f){\ensuremath{<}}5.6{$\times$}10{\^{ }}(?6). For the 600?1000 Hz band, ?\_(GW)(f){\ensuremath{<}}0.14(f/900 Hz){\^{ }}3, a factor of 2.5 lower than the best previously reported upper limits. We find ?\_(GW)(f){\ensuremath{<}}1.8{$\times$}10{\^{ }}(?4) using a spectral index of zero for 170?600 Hz and ?\_(GW)(f){\ensuremath{<}}1.0(f/1300 Hz){\^{ }}3 for 1000?1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.} }

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