TY - JOUR

T1 - Consistency of the expansion of the Universe with density perturbations

AU - Gannouji, Radouane

AU - Polarski, David

N1 - Funding Information:
The authors thank Benjamin L’Huillier for many helpful comments and for sharing with us compiled data used in this paper. The work of R. Gannouji is supported by Fondecyt project No. 1171384.
Publisher Copyright:
© 2018 American Physical Society.

PY - 2018/10/15

Y1 - 2018/10/15

N2 - Assuming a simple form for the growth index γ(z) depending on two parameters γ0≡γ(z=0) and γ1≡γ′(z=0), we show that these parameters can be constrained using background expansion data. We explore systematically the preferred region in this parameter space. Inside general relativity we obtain that models with a quasistatic growth index and γ1≈-0.02 are favored. We find further the lower bounds γ00.53 and γ1-0.15 for models inside GR. Models outside GR having the same background expansion as ΛCDM and arbitrary γ(z) with γ0=γ0ΛCDM, satisfy Geff,0>G for γ1>γ1ΛCDM, and Geff,0<G for γ1<γ1ΛCDM. The first models will cross downwards the value Geff=G on very low redshifts z<0.3, while the second models will cross upwards Geff=G in the same redshift range. This makes the realization of such modified gravity models even more problematic.

AB - Assuming a simple form for the growth index γ(z) depending on two parameters γ0≡γ(z=0) and γ1≡γ′(z=0), we show that these parameters can be constrained using background expansion data. We explore systematically the preferred region in this parameter space. Inside general relativity we obtain that models with a quasistatic growth index and γ1≈-0.02 are favored. We find further the lower bounds γ00.53 and γ1-0.15 for models inside GR. Models outside GR having the same background expansion as ΛCDM and arbitrary γ(z) with γ0=γ0ΛCDM, satisfy Geff,0>G for γ1>γ1ΛCDM, and Geff,0<G for γ1<γ1ΛCDM. The first models will cross downwards the value Geff=G on very low redshifts z<0.3, while the second models will cross upwards Geff=G in the same redshift range. This makes the realization of such modified gravity models even more problematic.

UR - http://www.scopus.com/inward/record.url?scp=85056184770&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.98.083533

DO - 10.1103/PhysRevD.98.083533

M3 - Article

AN - SCOPUS:85056184770

VL - 98

JO - Physical Review D

JF - Physical Review D

SN - 2470-0010

IS - 8

M1 - 083533

ER -