Cosmic string power spectrum, bispectrum, and trispectrum

Journal Article · Wed Sep 15 04:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.82.063527· OSTI ID:21421134

Regan, D M; Shellard, E P. S. ^[1]

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1. Centre for Theoretical Cosmology, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)

We use analytic calculations of the post-recombination gravitational effects of cosmic strings to estimate the resulting CMB power spectrum, bispectrum and trispectrum. We place a particular emphasis on multipole regimes relevant for forthcoming CMB experiments, notably the Planck satellite. These calculations use a flat-sky approximation, generalizing previous work by integrating string contributions from last scattering to the present day, finding the dominant contributions to the correlators for multipoles l>50. We find a well-behaved shape for the string bispectrum (without divergences) which is easily distinguishable from the inflationary bispectra which possess significant acoustic peaks. We estimate that the nonlinearity parameter characterizing the bispectrum is approximately 0 > or approx. f{sub NL} > or approx. -40 (given present string constraints from the CMB power spectrum). We also apply these unequal time correlator methods to calculate the trispectrum for parrallelogram configurations, again valid over a large range of angular scales relevant for WMAP and Planck, as well as on very small angular scales. We find that, unlike the bispectrum which is suppressed by symmetry considerations, the trispectrum for cosmic strings is large. Our current estimate for the trispectrum parameter is {tau}{sub NL{approx}}10{sup 5}, which may provide one of the strongest constraints on the string model in future analysis.

• OSTI ID: 21421134
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 6 Vol. 82; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
APPROXIMATIONS
CALCULATION METHODS
COMPOSITE MODELS
COSMIC RADIATION
ELECTROMAGNETIC RADIATION
EXTENDED PARTICLE MODEL
GRAVITATION
IONIZING RADIATIONS
MATHEMATICAL MODELS
MICROWAVE RADIATION
MULTIPOLES
NONLINEAR PROBLEMS
PARTICLE MODELS
PEAKS
QUARK MODEL
RADIATIONS
RECOMBINATION
RELICT RADIATION
SCATTERING
SIMULATION
SPECTRA
STRING MODELS
SYMMETRY