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120 results on '"Barreira, Alexandre"'

116. FrontMatter.

Author

Barreira, Alexandre

Published
2016

118. Modified gravity with massive neutrinos as a testable alternative cosmological model.

Author

Li, Baojiu, Baugh, Carlton M., Barreira, Alexandre, and Pascoli, Silvia

Subjects
*GRAVITATIONAL interactions, *NEUTRINOS, *COSMIC background radiation, *DARK matter, *SOLAR system
Abstract

We show that, in the presence of massive neutrinos, the Galileon gravity model provides a very good fit to the current cosmic microwave background (CMB) temperature, CMB lensing and baryonic acoustic oscillation data. This model, which we dub νGalileon, when assuming its stable attractor background solution, contains the same set of free parameters as lambda cold dark matter (ΛCDM), although it leads to different expansion dynamics and nontrivial gravitational interactions. The data provide compelling evidence (≳6σ) for nonzero neutrino masses, with σmν≳0.4 eV at the 2σ level. Upcoming precision terrestrial measurements of the absolute neutrino mass scale therefore have the potential to test this model. We show that CMB lensing measurements at multipoles l≲40 will be able to discriminate between the νGalileon and ΛCDM models. Unlike ΛCDM, the νGalileon model is consistent with local determinations of the Hubble parameter. The presence of massive neutrinos lowers the value of σ8 substantially, despite of the enhanced gravitational strength on large scales. Unlike ΛCDM, the νGalileon model predicts a negative ISW effect, which is difficult to reconcile with current observational limits. [ABSTRACT FROM AUTHOR]

Published
2014
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120. Modified gravity N-body code comparison project

Author

Ewald Puchwein, Claudio Llinares, Alexandre Barreira, Christian Arnold, Fabian Schmidt, Gong-Bo Zhao, Marco Baldi, Wojciech A. Hellwing, Bridget Falck, Hans A. Winther, Baojiu Li, David F. Mota, Robert E. Smith, Sownak Bose, Kazuya Koyama, Winther, Hans A, Schmidt, Fabian, Barreira, Alexandre, Arnold, Christian, Bose, Sownak, Llinares, Claudio, Baldi, Marco, Falck, Bridget, Hellwing, Wojciech A., Koyama, Kazuya, Li, Baojiu, Mota, David F., Puchwein, Ewald, Smith, Robert E., and Zhao, Gong-Bo

Subjects
Gravity (chemistry), Cosmology and Gravitation, Cold dark matter, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Large-scale structure of Universe, General relativity, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, General Relativity and Quantum Cosmology (gr-qc), General Relativity and Quantum Cosmology, Many-body problem, Quantum mechanics, Limit (mathematics), Statistical physics, STFC, QB, Physics, Matter power spectrum, RCUK, Astronomy and Astrophysics, Observable, Space and Planetary Science, astro-ph.CO, Halo, large-scale structure of Universe, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

Self-consistent ${\it N}$-body simulations of modified gravity models are a key ingredient to obtain rigorous constraints on deviations from General Relativity using large-scale structure observations. This paper provides the first detailed comparison of the results of different ${\it N}$-body codes for the $f(R)$, DGP, and Symmetron models, starting from the same initial conditions. We find that the fractional deviation of the matter power spectrum from $\Lambda$CDM agrees to better than $1\%$ up to $k \sim 5-10~h/{\rm Mpc}$ between the different codes. These codes are thus able to meet the stringent accuracy requirements of upcoming observational surveys. All codes are also in good agreement in their results for the velocity divergence power spectrum, halo abundances and halo profiles. We also test the quasi-static limit, which is employed in most modified gravity ${\it N}$-body codes, for the Symmetron model for which the most significant non-static effects among the models considered are expected. We conclude that this limit is a very good approximation for all of the observables considered here., Comment: 31 pages, 16 figures. Version to appear in MNRAS

Published
2015

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