Cosmological constraints on the very low frequency gravitational-wave background
- Theoretical Astrophysics, California Institute of Technology, MC 130-33, Pasadena, California 91125 (United States)
- Department of Physics and Astronomy, University of California, 4186 Frederick Reines Hall, Irvine, California 92697 (United States)
The curl modes of cosmic microwave background polarization allow one to indirectly constrain the primordial background of gravitational waves with frequencies around 10{sup -18} to 10{sup -16} Hz. The proposed high precision timing observations of a large sample of millisecond pulsars with the pulsar timing array or with the square kilometer array can either detect or constrain the stochastic gravitational-wave background at frequencies greater than roughly 0.1 yr{sup -1}. While existing techniques are limited to either observe or constrain the gravitational-wave background across six or more orders of magnitude between 10{sup -16} and 10{sup -10} Hz, we suggest that the anisotropy pattern of time variation of the redshift related to a sample of high-redshift objects can be used to study the background around a frequency of 10{sup -12} Hz. Useful observations to detect an anisotropy signal in the global redshift change include spectroscopic observations of the Ly-{alpha} forest in absorption towards a sample of quasars, redshifted 21 cm line observations either in absorption or emission towards a sample of neutral HI regions before or during reionization, and high-frequency (0.1 to 1 Hz) gravitational-wave analysis of a sample of neutron star-neutron star binaries detected with gravitational-wave instruments such as the Decihertz Interferometer Gravitational Wave Observatory (DECIGO). For reasonable observations expected in the future involving extragalactic sources, we find limits at the level of {omega}{sub GW}<10{sup -6} at a frequency around 10{sup -12} Hz while the ultimate limit is likely to be around {omega}{sub GW}<10{sup -11}. On the other hand, if there is a background of gravitational waves at 10{sup -12} Hz with an amplitude larger than this limit, its presence will be visible as a measurable anisotropy in the time-evolving redshift of extragalactic sources.
- OSTI ID:
- 20795688
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 73, Issue 2; Other Information: DOI: 10.1103/PhysRevD.73.023005; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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