Browsing by Author "Bellini, Emilio"

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    A comparison of Einstein-Boltzmann solvers for testing General Relativity
    (American Physical Society, 2018) Bellini, Emilio; Barreira, A.; Frusciante, N.; Ballardini, M.
    We compare Einstein-Boltzmann solvers that include modifications to General Relativity and find that, for a wide range of models and parameters, they agree to a high level of precision. We look at three general purpose codes that primarily model general scalar-tensor theories, three codes that model Jordan-Brans-Dicke (JBD) gravity, a code that models f (R) gravity, a code that models covariant Galileons, a code that models Hoˇrava- Lifschitz gravity and two codes that model non-local models of gravity. Comparing predictions of the angular power spectrum of the cosmic microwave background and the power spectrum of dark matter for a suite of different models, we find agreement at the sub-percent level. This means that this suite of Einstein-Boltzmann solvers is now sufficiently accurate for precision constraints on cosmological and gravitational parameters.
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    Matter bispectrum in cubic Galileon cosmologies
    (IOP Science, 2013) Bartolo, Nicola; Bellini, Emilio; Bertacca, Daniele; Matarrese, Sabino
    In this paper we obtain the bispectrum of dark matter density perturbations in the frame of covariant cubic Galileon theories. This result is obtained by means of a semi- analytic approach to second-order perturbations in Galileon cosmologies, assuming Gaussian initial conditions. In particular, we show that, even in the presence of large deviations of the linear growth-rate w.r.t. the CDM one, at the bispectrum level such deviations are reduced to a few percent.