2007/02/28 by Matthew R Depies, Matthew R. DePies, Craig J. Hogan · 3 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1103/physrevd.75.125006
published as Phys.Rev.D75:125006,2007 · 14 pgs, 7 fig, small text addition and reference added, accepted by Phys. Rev. D
arxiv created 2007/05/11 · openalex publication_date 2007/06/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Spectra of the stochastic gravitational wave backgrounds from cosmic strings are calculated and compared with present and future experimental limits. Motivated by theoretical expectations of light cosmic strings in superstring cosmology, improvements in experimental sensitivity, and recent demonstrations of large, stable loop formation from a primordial network, this study explores a new range of string parameters with masses lighter than previously investigated. A standard ``one-scale'' model for string loop formation is assumed. Background spectra are calculated numerically for dimensionless string tensions G\ensuremathμ/c2 between 10^\ensuremath-7 and 10^\ensuremath-18, and initial loop sizes as a fraction of the Hubble radius \ensuremathα from 0.1 to 10^\ensuremath-6. The spectra show a low frequency power-law tail, a broad spectral peak due to loops decaying at the present epoch (including frequencies higher than their fundamental mode, and radiation associated with cusps), and a flat (constant energy density) spectrum at high frequencies due to radiation from loops that decayed during the radiation-dominated era. The string spectrum is distinctive and unlike any other known source. The peak of the spectrum for light strings appears at high frequencies, significantly affecting predicted signals. The spectra of the cosmic string backgrounds are compared with current millisecond pulsar limits and Laser Interferometer Space Antenna (LISA) sensitivity curves. For models with large stable loops (\ensuremathα=0.1), current pulsar-timing limits exclude G\ensuremathμ/c2>10^\ensuremath-9, a much tighter limit on string tension than achievable with other techniques, and within the range of current models based on brane inflation. LISA may detect a background from strings as light as G\ensuremathμ/c2\ensuremath≈10^\ensuremath-16, corresponding to field theory strings formed at roughly 1011 GeV.