CMB constraints on cosmic strings and superstrings

Charnock, Tom; Avgoustidis, Anastasios; Copeland, Edmund J.; Moss, A.

doi:10.1103/physrevd.93.123503

Cited by 123 publications

(105 citation statements)

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“…Since our article appeared in the e-print archive, further work has been done using the unconnected segment model to approximate the cosmic string network [50]. The free parameters of the model can be tuned to mimic the TT power spectrum of an Abelian Higgs network, and the resulting BB spectrum also agrees quite well.…”

Section: Discussionmentioning

confidence: 99%

Energy-momentum correlations for Abelian Higgs cosmic strings

et al. 2016

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We report on the energy-momentum correlators obtained with recent numerical simulations of the Abelian Higgs model, essential for the computation of cosmic microwave background and matter perturbations of cosmic strings. Due to significant improvements both in raw computing power and in our parallel simulation framework, the dynamical range of the simulations has increased fourfold both in space and time, and for the first time we are able to simulate strings with a constant physical width in both the radiation and matter eras. The new simulations improve the accuracy of the measurements of the correlation functions at the horizon scale and confirm the shape around the peak. The normalization is slightly higher in the high wave-number tails, due to a small increase in the string density. We study, for the first time, the behavior of the correlators across cosmological transitions and discover that the correlation functions evolve adiabatically; i.e., the network adapts quickly to changes in the expansion rate. We propose a new method for constructing source functions for Einstein-Boltzmann integrators, comparing it with two other methods previously used. The new method is more consistent, easier to implement, and significantly more accurate.

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Section: Discussionmentioning

confidence: 99%

Energy-momentum correlations for Abelian Higgs cosmic strings

et al. 2016

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“…This constraint is conservative in the sense that it is the maximum tension allowed by CMB data independently of the value of g s and w. This constraint is approximately two orders of magnitude weaker than the constrains on cosmic superstrings that result from primary CMB anisotropies [105]: Gµ F < 2.8×10 −8 . Note however that the constraints for w = 0.1 and g s = 0.04 are slightly stronger: Gµ F < 1.9 × 10 −8 .…”

Section: A Cmb Constraintsmentioning

confidence: 98%

“…[105]) and it is merely the constraint that results from F-strings only. Note however that these constraints go significantly beyond the conservative limit in Eq.…”

Section: Figmentioning

confidence: 99%

Probing cosmic superstrings with gravitational waves

Sousa

Avelino

2016

Phys. Rev. D

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We compute the stochastic gravitational wave background generated by cosmic superstrings using a semi-analytical velocity-dependent model to describe their dynamics. We show that heavier string types may leave distinctive signatures on the stochastic gravitational wave background spectrum within the reach of present and upcoming gravitational wave detectors. We examine the physically motivated scenario in which the physical size of loops is determined by the gravitational backreaction scale and use NANOGRAV data to derive a conservative constraint of GµF < 3.2 × 10 −9 on the tension of fundamental strings. We demonstrate that approximating the gravitational wave spectrum generated by cosmic superstring networks using the spectrum generated by ordinary cosmic strings with reduced intercommuting probability (which is often done in the literature) leads, in general, to weaker observational constraints on GµF . We show that the inclusion of heavier string types is required for a more accurate characterization of the region of the (gs, GµF ) parameter space that may be probed using direct gravitational wave detectors. In particular, we consider the observational constraints that result from NANOGRAV data and show that heavier strings generate a secondary exclusion region of parameter space.

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“…Current constraints on the string tension depend on the string model and simulation technique adopted. For Nambu-Goto strings, power spectrum analyses based on simulations computed by the unconnected segment model (USM; Albrecht et al 1997Albrecht et al , 1999Pogosian & Vachaspati 1999) constrain the string tension to Gµ < 1.3 × 10 −7 (Planck Collaboration XXV 2014) using Planck temperature data and to Gµ < 1.1 × 10 −7 (Charnock et al 2016) when Planck polarisation data are also included. Recombination effects have been considered by Regan & Hindmarsh (2015) but were found not to have a significant effect on the bispectrum.…”

Section: Introductionmentioning

confidence: 99%

“…Various methods have been developed to search for stringinduced contributions to the CMB, from power-spectrum constraints (Lizarraga et al 2014a(Lizarraga et al ,b, 2016Charnock et al 2016), to higher-order statistics such as the bispectrum (Planck Collaboration XXV 2014; Regan & Hindmarsh 2015) and trispectrum (Fergusson et al 2010), and tools such as edge detection (Lo & Wright 2005;Amsel et al 2008;Stewart & Brandenberger 2009;Danos & Brandenberger 2010), Minkowski functionals (Gott et al 1990;Ducout et al 2013;Planck Collaboration XXV 2014), wavelets and curvelets (Starck et al 2004;Hammond et al 2009;Wiaux et al 2010;Planck Collaboration XXV 2014;Hergt et al 2016), level crossings (Sadegh Movahed & Khosravi 2011), and peakpeak correlations (Movahed et al 2013). Current constraints on the string tension depend on the string model and simulation technique adopted.…”

Section: Introductionmentioning

confidence: 99%

Wavelet-Bayesian inference of cosmic strings embedded in the cosmic microwave background

McEwen

Feeney

Peiris

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Cosmic strings are a well-motivated extension to the standard cosmological model and could induce a subdominant component in the anisotropies of the cosmic microwave background (CMB), in addition to the standard inflationary component. The detection of strings, while observationally challenging, would provide a direct probe of physics at very high energy scales. We develop a framework for cosmic string inference from observations of the CMB made over the celestial sphere, performing a Bayesian analysis in wavelet space where the string-induced CMB component has distinct statistical properties to the standard inflationary component. Our wavelet-Bayesian framework provides a principled approach to compute the posterior distribution of the string tension Gµ and the Bayesian evidence ratio comparing the string model to the standard inflationary model. Furthermore, we present a technique to recover an estimate of any string-induced CMB map embedded in observational data. Using Planck-like simulations we demonstrate the application of our framework and evaluate its performance. The method is sensitive to Gµ ∼ 5 × 10 −7 for Nambu-Goto string simulations that include an integrated Sachs-Wolfe (ISW) contribution only and do not include any recombination effects, before any parameters of the analysis are optimised. The sensitivity of the method compares favourably with other techniques applied to the same simulations.

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CMB constraints on cosmic strings and superstrings

Cited by 123 publications

References 123 publications

Energy-momentum correlations for Abelian Higgs cosmic strings

Energy-momentum correlations for Abelian Higgs cosmic strings

Probing cosmic superstrings with gravitational waves

Wavelet-Bayesian inference of cosmic strings embedded in the cosmic microwave background

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