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Constraining cosmological ultra-large scale structure using numerical relativity

Braden, J; Johnson, MC; Peiris, HV; Aguirre, A; (2017) Constraining cosmological ultra-large scale structure using numerical relativity. Physical Review D , 96 , Article 023541. 10.1103/PhysRevD.96.023541. Green open access

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Abstract

Cosmic inflation, a period of accelerated expansion in the early universe, can give rise to large amplitude ultra-large scale inhomogeneities on distance scales comparable to or larger than the observable universe. The cosmic microwave background (CMB) anisotropy on the largest angular scales is sensitive to such inhomogeneities and can be used to constrain the presence of ultra-large scale structure (ULSS). We numerically evolve nonlinear inhomogeneities present at the beginning of inflation in full General Relativity to assess the CMB quadrupole constraint on the amplitude of the initial fluctuations and the size of the observable universe relative to a length scale characterizing the ULSS. To obtain a statistically meaningful ensemble of simulations, we adopt a toy model in which inhomogeneities are injected along a preferred direction. We compute the likelihood function for the CMB quadrupole including both ULSS and the standard quantum fluctuations produced during inflation. We compute the posterior given the observed CMB quadrupole, finding that when including gravitational nonlinearities, ULSS curvature perturbations of order unity are allowed by the data, even on length scales not too much larger than the size of the observable universe. Our results illustrate the utility and importance of numerical relativity for constraining early universe cosmology.

Type: Article
Title: Constraining cosmological ultra-large scale structure using numerical relativity
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevD.96.023541
Publisher version: https://doi.org/10.1103/PhysRevD.96.023541
Language: English
Additional information: his version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Evolution of the Universe, Fluids & classical fields in curved spacetime, Inflation, Relativistic aspects of cosmology,Astrophysical & cosmological simulations, Numerical relativity
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/1503944
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