Testing for gravitational preferred directions with galaxy and lensing surveys

Abstract

We analyze the sensitivity of galaxy and weak-lensing surveys to detect preferred directions in the gravitational interaction. We consider general theories of gravity involving additional vector degrees of freedom with non-vanishing spatial components in the background. We use a modelindependent parametrization of the perturbations equations in terms of four effective parameters, namely, the standard effective Newton constant G ef f and slip parameter γ for scalar modes and two new parameters µQ and µ h for vector and tensor modes respectively, which are required when preferred directions are present. We obtain the expressions for the multipole galaxy power spectrum in redshift space and for the weak-lensing shear, convergence and rotation spectra in the presence of preferred directions. By performing a Fisher matrix forecast analysis, we estimate the sensitivity of a future Euclid-like survey to detect this kind of modification of gravity. We finally compare with the effects induced by violations of statistical isotropy in the primordial power spectrum and identify the observables which could discriminate between them.PACS numbers: 04.50. Kd, 98.80.-k, 98.80.Cq, 12.60.-i arXiv:1907.12285v1 [astro-ph.CO]

Modified gravity or imperfect dark matter: a model-independent discrimination

“…If we assume the coefficients a ij and b ij to be quadratic in k, we recover the explicit expressions for µ and γ obtained in [44]. Here, we remark the fact that, in the quasi-static approximation, a general modification of gravity with additional scalar degrees of freedom can be characterized by two functions µ(k, a) and γ(k, a) (see [45,46] for the vector case).…”

The Fisher gAlaxy suRvey cOde (FARO)

“…Galaxy surveys are able to measure also the shapes and sizes of galaxies. In the standard case, this information is encoded in the convergence power spectrum (see however [36,37] for a more general analysis). Thus, the convergence angular power spectra for galaxies in redshift bins i and j reads [38],…”

Detectable Data-driven Features in the Primordial Scalar Power Spectrum

“…However, there is still observational room for small deviations from this prediction. Several authors have investigated the sensitivity of future measurements of matter distribution to the physics of early Universe and estimated the detectability of the traces left by various early universe scenarios on the matter distribution (see, e.g., Fedeli et al 2011;Huang et al 2012;Fedeli & Moscardini 2012;Ballardini et al 2019;Resco & Maroto 2020;Debono et al 2020).…”