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Fluctations in the cosmic microwave background arising from low‐frequency gravitational radiation
Author(s) -
Dautcourt G.
Publication year - 1974
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.19742950303
Subject(s) - physics , cosmic microwave background , gravitational wave , black body radiation , astrophysics , gravitational energy , cosmic background radiation , amplitude , intergalactic travel , universe , gravitational field , gravitational redshift , astronomy , radiation , galaxy , anisotropy , quantum mechanics , redshift
Intense low‐frequency intergalactic gravitational radiation with wave lengths λ smaller than the H UBBLE distance λ H ≌ 3000 (100/ H 0 ) Mpc but not exceedingly small compared to λ H . generates anisotropies in the microwave background radiation. One contribution results from the local wave field and produces mainly a quadrupole‐type temperature variation on the sky. Available data on large‐scale microwave fluctuations do not exclude appreciable amounts of gravitational background radiation in the Megaparsec wave band. A more sensitive test is provided by a second far‐field contribution, which has a small angular scale. Its amplitude depends strongly on the ratio of the (present) rest mass density to the H UBBLE constant, if a cosmological origin of the blackbody radiation is assumed. In a low‐density universe, pre‐galactic C OMPTON scattering of the blackbody radiation is not able to reduce the fluctuations caused by the low‐frequency gravitational wave field. The recent small‐scale data by P ARIJSKIJ would allow only small amplitudes of gravitational waves with an energy density significantly below the critical cosmological density. On the other hand, in a high‐density universe, the small angular scale fluctuation in the blackbody radiation is completely damped out, and a gravitational radiation cosmos reaching the critical density is admitted. Independent of the matter density, the data by P ARIJSKIJ would confine gravitational background radiation to insignificant amplitudes if a discrete source model for the origin of the microwave background has to be assumed.