Gravité modifiée

5 articles

Un test de la relativité générale indépendant de tout modèle

Avec Arman Shafieloo et Hyungjin Kim (Université de Waterloo), nous avons combiné des reconstructions de l’histoire de l’expansion indépendantes de tout modèle, obtenues à partir des supernovae et des BAO, avec les mesures de croissance issues des distorsions dans l’espace des redshifts, et obtenu des contraintes indépendantes de tout modèle sur la densité de matière $\Omega_\mathrm{m}$ , l’amplitude des fluctuations $\sigma_8$ et l’indice de croissance $\gamma$ , défini par

f(z) \equiv \frac{\mathrm{d}\ln\delta}{\mathrm{d}\ln a} \simeq \Omega_\mathrm{m}(z)^{\gamma},

avec $\gamma \simeq 0.55$ en relativité générale. Nos résultats sont compatibles avec $\Lambda$ CDM + RG (L'Huillier, Shafieloo & Kim 2018, MNRAS 476, 3263).

Avec Arman Shafieloo et Alexeï Starobinsky, nous avons ensuite combiné les données de supernovae de type Ia les plus récentes (Pantheon) avec des mesures de croissance (dont eBOSS DR14Q), et obtenu des contraintes plus fortes, toujours compatibles avec $\Lambda$ CDM + RG (Shafieloo, L'Huillier & Starobinsky 2018, PRD 98, 083526).

Contraintes sur l’indice de croissance gamma et sigma_8 issues de tests de ΛCDM indépendants de tout modèle — Tests du modèle ΛCDM — Shafieloo, L'Huillier & Starobinsky (2018), Physical Review D.

Realistic forecast: reconstructed Geff/G and fsigma8 for two modified-gravity scenarios (bump and dip). Both rule out GR at more than 2sigma around z approx 1. — Realistic forecast: reconstructed $G_\mathrm{eff}/G$ and $f\sigma_8$ for two modified-gravity scenarios (bump and dip). Both rule out GR at more than $2\sigma$ around $z \approx 1$ .

2023 · Phys. Rev. D 108 (2023) 023504

Joint reconstructions of growth and expansion histories from stage-IV surveys with minimal assumptions. II. Modified gravity and massive neutrinos

Calderón, R., L'Huillier, B., Polarski, D., Shafieloo, A., Starobinsky, A. A.

We reconstruct the effective gravitational coupling $G_\mathrm{eff}(z)$ as a Gaussian process from forecast stage-IV growth data. DESI-like surveys could detect departures from General Relativity if dark energy is well determined; massive neutrinos do not change this, but assuming a ΛCDM expansion biases the inferred $\Omega_\mathrm{m}$ and $\sigma_8$ .

DOI · arXiv:2301.00640

Gravité modifiée Croissance des structures (RSD)Processus gaussiens

Reconstructions of Omegade(z) (left) and the growth index gamma(z) (right) that fit the growth data better than ΛCDM, for three cases. — Reconstructions of $\Omega_\mathrm{de}(z)$ (left) and the growth index $\gamma(z)$ (right) that fit the growth data better than ΛCDM, for three cases.

2020 · MNRAS 494 (2020) 819

Defying the laws of Gravity I: model-independent reconstruction of the Universe expansion from growth data

L'Huillier, B., Shafieloo, A., Polarski, D., Starobinsky, A. A.

From redshift-space distortion data alone, we reconstruct the growth history with crossing statistics and Gaussian processes, derive the expansion history from it, and fit supernovae to constrain $\Omega_{\mathrm{m},0}$ and $\sigma_{8,0}$ . The results are consistent with flat ΛCDM and General Relativity.

DOI · arXiv:1906.05991

Gravité modifiée Croissance des structures (RSD)Supernovae Ia Processus gaussiens Premier auteur

Theta(z) (top) and Ok(z) (bottom) from supernovae and BOSS/eBOSS BAO. A flat FLRW universe gives Theta = 1. — $\Theta(z)$ (top) and $\mathcal{O}_k(z)$ (bottom) from supernovae and BOSS/eBOSS BAO. A flat FLRW universe gives $\Theta = 1$ .

2018 · Phys. Rev. D 98 (2018) 083526

Falsifying ΛCDM: model-independent tests of the concordance model with eBOSS DR14Q and Pantheon

Shafieloo, A., L'Huillier, B.*, Starobinsky, A. A.

Combining model-independent expansion reconstructions from Pantheon supernovae and BAO, we test the FLRW metric and flatness, and use eBOSS DR14Q growth data to constrain $\Omega_\mathrm{m}$ , $\gamma$ and $\sigma_8$ . Everything is consistent with a flat FLRW universe, General Relativity and $\Lambda$ , with some tension at $z > 1$ .

DOI · arXiv:1804.04320

Articles clés Courbure et FLRW Gravité modifiée Supernovae Ia BAO Croissance des structures (RSD)Lissage itératif

Model-independent regions allowed by growth data (blue) compared with ΛCDM (red), at fixed gamma = 0.55 (left) and fixed sigma8 = 0.8 (right). — Model-independent regions allowed by growth data (blue) compared with ΛCDM (red), at fixed $\gamma = 0.55$ (left) and fixed $\sigma_8 = 0.8$ (right).

2018 · MNRAS 476 (2018) 3263

Model-independent cosmological constraints from growth and expansion

L'Huillier, B., Shafieloo, A., Kim, H.†

We reconstruct the expansion history from supernovae and fit growth-rate data to constrain $\Omega_\mathrm{m}$ , the growth index $\gamma$ and $\sigma_8$ without a dark energy model. The results agree with ΛCDM in General Relativity, and requiring a positive dark energy density tightens them further.

DOI · arXiv:1712.04865

Articles clés Gravité modifiée Supernovae Ia Croissance des structures (RSD)Premier auteur Avec mes étudiants

Halo interaction rate versus mass in ΛCDM and in f(R), DGP and coupled dark energy simulations. — Halo interaction rate versus mass in ΛCDM and in $f(R)$ , DGP and coupled dark energy simulations.

Des halos au-delà de la relativité générale

2017 · MNRAS 468 (2017) 3174

Dark matter haloes in modified gravity and dark energy: interaction rate, small- and large-scale alignment

L'Huillier, B., Winther, H. A., Mota, D. F., Park, C., Kim, J.

In N-body simulations of $f(R)$ gravity, DGP and coupled dark energy, $f(R)$ raises halo spin and weakens the spin alignment of interacting pairs, while only strongly coupled dark energy increases the halo interaction rate and the alignment of halo shapes with the large-scale structure.

DOI · arXiv:1703.07357

Articles clés Gravité modifiée Énergie noire Halos de matière noire Simulations Premier auteur

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