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New Cosmic Microwave Background Constraint to Primordial Gravitational Waves

Smith, Tristan L. and Pierpaoli, Elena and Kamionkowski, Marc (2006) New Cosmic Microwave Background Constraint to Primordial Gravitational Waves. Physical Review Letters, 97 (2). Art. No. 021301. ISSN 0031-9007. doi:10.1103/PhysRevLett.97.021301.

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Primordial gravitational waves (GWs) with frequencies >~10^-15 Hz contribute to the radiation density of the Universe at the time of decoupling of the cosmic microwave background (CMB). This affects the CMB and matter power spectra in a manner identical to massless neutrinos, unless the initial density perturbation for the GWs is nonadiabatic, as may occur if such GWs are produced during inflation or some post-inflation phase transition. In either case, current observations provide a constraint to the GW amplitude that competes with that from big-bang nucleosynthesis (BBN), although it extends to much lower frequencies (~10^-15 Hz rather than the ~10^-10 Hz from BBN): at 95% confidence level, Omegagwh2<~8.4×10^-6 for homogeneous (i.e., nonadiabatic) initial conditions. Future CMB experiments, like Planck and CMBPol, should allow sensitivities to Omegagwh2<~1.4×10^-6 and Omegagwh2<~5×10^-7, respectively.

Item Type:Article
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Pierpaoli, Elena0000-0002-7957-8993
Kamionkowski, Marc0000-0001-7018-2055
Additional Information:© 2006 The American Physical Society (Received 6 March 2006; revised 26 May 2006; published 14 July 2006) T.L.S. was supported by the NSF. E.P. was supported by NSF Grant No. AST-0340648, also supported by NASA Grant No. NAG5-11489. This work was supported in part by DOE Grant No. DE-FG03-92-ER40701 and NASA Grant No. NNG05GF69G. This work was supported in part by the NSF through the TeraGrid resources provided by NCSA and SDSC under TeraGrid Grant No. AST050005T.
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Department of Energy (DOE)DE-FG03-92-ER40701
Issue or Number:2
Record Number:CaltechAUTHORS:SMIprl06
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5372
Deposited By: Archive Administrator
Deposited On:16 Oct 2006
Last Modified:08 Nov 2021 20:25

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