4 research outputs found
Evolution of matter density perturbations in viable f (R) theories of gravity
In the ΛCDM model, the late-time accelerated expansion of the Universe is explained via a dark energy fluid in the form of a cosmological constant. Such a cosmological constant dominates the energy budget of the Universe today, and yet, it is still a poorly understood species because it is not observed yet. A competitive theoretical approach to understand this is via the so-called f (R) extended theories of gravity, which explain the late acceleration epoch of the Universe resorting to a geometrical modification of the field equations. We illustrate how f (R) theories are constructed and how both the analysis of the cosmological expansion and the growth of matter density perturbations in these theories may differ from the standard Einsteinian results. We study the evolution of matter density perturbations in a viable f (R) model (Hu-Sawicki model) and explain why the Hu-Sawicki model is indeed a viable alternative to ΛCDM by discussing the Dynamical System approach as a method used to obtain the cosmological background solutions. A complete comparison of density perturbations in both the ΛCDM model and Hu-Sawicki model is presented
Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
Surveys of the matter distribution contain `fossil' information on possible
non-Gaussianity that is generated in the primordial Universe. This primordial
signal survives only on the largest scales where cosmic variance is strongest.
By combining different surveys in a multi-tracer approach, we can suppress the
cosmic variance and significantly improve the precision on the level of
primordial non-Gaussianity. We consider a combination of an optical galaxy
survey, like the recently initiated DESI survey, together with a new and very
different type of survey, a 21 cm intensity mapping survey, like the upcoming
SKAO survey. A Fisher forecast of the precision on the local primordial
non-Gaussianity parameter , shows that this multi-tracer
combination, together with non-overlap single-tracer information, can deliver
precision comparable to that from the CMB. Taking account of the largest
systematic, i.e. foreground contamination in intensity mapping, we find that
.Comment: 10+5 pages, 4 figures, "Minor corrections, main results unchanged.
Version accepted by EPJC
Constraining primordial non-Gaussianity by combining next-generation galaxy and 21 cm intensity mapping surveys
Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in
the primordial universe. This primordial signal survives only on the largest scales where cosmic variance is strongest. By
combining different surveys in a multi-tracer approach, we can suppress the cosmic variance and significantly improve
the precision on the level of primordial non-Gaussianity.We consider a combination of an optical galaxy survey, like the
recently initiated DESI survey, together with a new and very different type of survey, a 21cm intensity mapping survey,
like the upcoming SKAO survey. A Fisher forecast of the precision on the local primordial non-Gaussianity parameter
fNL, shows that this multi-tracer combination, together with non-overlap single-tracer information, can deliver precision
comparable to that from the CMB. Taking account of the largest systematic, i.e. foreground contamination in intensity
mapping, we find that σ( fNL) ∼
Constraining primordial non-Gaussianity by combining next-generation galaxy and 21Â cm intensity mapping surveys
Abstract Surveys of the matter distribution contain ‘fossil’ information on possible non-Gaussianity that is generated in the primordial Universe. This primordial signal survives only on the largest scales where cosmic variance is strongest. By combining different surveys in a multi-tracer approach, we can suppress the cosmic variance and significantly improve the precision on the level of primordial non-Gaussianity. We consider a combination of an optical galaxy survey, like the recently initiated DESI survey, together with a new and very different type of survey, a 21 cm intensity mapping survey, like the upcoming SKAO survey. A Fisher forecast of the precision on the local primordial non-Gaussianity parameter f NL , shows that this multi-tracer combination, together with non-overlap single-tracer information, can deliver precision comparable to that from the CMB. Taking account of the largest systematic, i.e. foreground contamination in intensity mapping, we find that σ ( f NL ) ∼ 4