scholarly journals Cosmic degeneracies – I. Joint N-body simulations of modified gravity and massive neutrinos

2014 ◽  
Vol 440 (1) ◽  
pp. 75-88 ◽  
Author(s):  
Marco Baldi ◽  
Francisco Villaescusa-Navarro ◽  
Matteo Viel ◽  
Ewald Puchwein ◽  
Volker Springel ◽  
...  
Keyword(s):  
Modified Gravity ◽  
Massive Neutrinos

scholarly journals Cluster counts

2019 ◽  
Vol 631 ◽  
pp. A96 ◽  
Author(s):  
Stéphane Ilić ◽  
Ziad Sakr ◽  
Alain Blanchard
Keyword(s):  
Modified Gravity ◽  
Cold Dark Matter ◽  
Power Spectra ◽  
Growth Index ◽  
New Physics ◽  
X Ray ◽  
Standard Value ◽  
Massive Neutrinos ◽  
Mass Calibration ◽  
Two Parameters

The Lambda cold dark matter (ΛCDM) concordance model is very successful at describing our Universe with high accuracy and only a few parameters. Despite its successes, a few tensions persist; most notably, the best-fit ΛCDM model, as derived from the Planck cosmic microwave background (CMB) data, largely overpredicts the abundance of Sunyaev–Zel’dovich (SZ) clusters when using their standard mass calibration. Whether this is the sign of an incorrect calibration or the need for new physics remains a matter of debate. In this study, we examined two simple extensions of the standard model and their ability to release the aforementioned tension: massive neutrinos and a simple modified gravity model via a non-standard growth index γ. We used both the Planck CMB power spectra and SZ cluster counts as datasets, alone and in combination with local X-ray clusters. In the case of massive neutrinos, the cluster-mass calibration (1 − b) is constrained to 0.585+0.031−0.037 (68% limits), more than 5σ away from its standard value (1 − b)∼0.8. We found little correlation between neutrino masses and cluster calibration, corroborating previous conclusions derived from X-ray clusters; massive neutrinos do not alleviate the cluster-CMB tension. With our simple γ model, we found a large correlation between the calibration and the growth index γ, but contrary to local X-ray clusters, SZ clusters are able to break the degeneracy between the two parameters thanks to their extended redshift range. The calibration (1 − b) was then constrained to 0.602+0.053−0.065, leading to an interesting constraint on γ = 0.60 ± 0.13. When both massive neutrinos and modified gravity were allowed, preferred values remained centred on standard ΛCDM values, but a calibration (1 − b)∼0.8 was allowed (though only at the 2σ level) provided ∑mν ∼ 0.34 eV and γ ∼ 0.8. We conclude that massive neutrinos do not relieve the cluster-CMB tension, and that a calibration close to the standard value (1 − b)∼0.8 would call for new physics in the gravitational sector.

scholarly journals Modified gravity with massive neutrinos as a testable alternative cosmological model

2014 ◽  
Vol 90 (2) ◽  
Author(s):  
Alexandre Barreira ◽  
Baojiu Li ◽  
Carlton M. Baugh ◽  
Silvia Pascoli
Keyword(s):  
Cosmological Model ◽  
Modified Gravity ◽  
Massive Neutrinos

scholarly journals Higher order spectra of weak lensing convergence maps in parametrized theories of modified gravity

2020 ◽  
Vol 498 (4) ◽  
pp. 5299-5316
Author(s):  
D Munshi ◽  
J D McEwen
Keyword(s):  
Modified Gravity ◽  
Arbitrary Order ◽  
Higher Order ◽  
Tree Level ◽  
Weak Lensing ◽  
The Family ◽  
Normal Branch ◽  
Massive Neutrinos ◽  
Higher Order Spectra ◽  
Good Agreement

ABSTRACT We compute the low-ℓ limit of the family of higher order spectra for projected (2D) weak lensing convergence maps. In this limit these spectra are computed to an arbitrary order using tree-level perturbative calculations. We use the flat-sky approximation and Eulerian perturbative results based on a generating function approach. We test these results for the lower order members of this family, i.e. the skew- and kurt-spectra against state-of-the-art simulated all-sky weak lensing convergence maps and find our results to be in very good agreement. We also show how these spectra can be computed in the presence of a realistic sky-mask and Gaussian noise. We generalize these results to 3D and compute the equal-time higher order spectra. These results will be valuable in analysing higher order statistics from future all-sky weak lensing surveys such as the Euclid survey at low-ℓ modes. As illustrative examples, we compute these statistics in the context of the Horndeski and beyond Horndeski theories of modified gravity. They will be especially useful in constraining theories such as the Gleyzes–Langlois–Piazza–Vernizzi (GLPV) theories and degenerate higher order scalar-tensor theories as well as the commonly used normal-branch of Dvali–Gabadadze–Porrati model, clustering quintessence models and scenarios with massive neutrinos.

scholarly journals Investigating the degeneracy between modified gravity and massive neutrinos with redshift-space distortions

2019 ◽  
Vol 2019 (06) ◽  
pp. 040-040 ◽  
Author(s):  
Bill S. Wright ◽  
Kazuya Koyama ◽  
Hans A. Winther ◽  
Gong-Bo Zhao
Keyword(s):  
Modified Gravity ◽  
Massive Neutrinos

scholarly journals Joint halo-mass function for modified gravity and massive neutrinos – I. Simulations and cosmological forecasts

2019 ◽  
Vol 486 (3) ◽  
pp. 3927-3941 ◽  
Author(s):  
Steffen Hagstotz ◽  
Matteo Costanzi ◽  
Marco Baldi ◽  
Jochen Weller
Keyword(s):  
Modified Gravity ◽  
Mass Function ◽  
Massive Neutrinos

scholarly journals Breaking cosmic degeneracies: Disentangling neutrinos and modified gravity with kinematic information

2019 ◽  
Vol 629 ◽  
pp. A46 ◽  
Author(s):  
Steffen Hagstotz ◽  
Max Gronke ◽  
David F. Mota ◽  
Marco Baldi
Keyword(s):  
Growth Rate ◽  
Power Spectrum ◽  
Modified Gravity ◽  
Large Scale ◽  
Density Fluctuations ◽  
Gravity Models ◽  
Neutrino Masses ◽  
Matter Power Spectrum ◽  
Massive Neutrinos ◽  
Kinematic Information

Searches for modified gravity in the large-scale structure try to detect the enhanced amplitude of density fluctuations caused by the fifth force present in many of these theories. Neutrinos, on the other hand, suppress structure growth below their free-streaming length. Both effects take place on comparable scales, and uncertainty in the neutrino mass leads to a degeneracy with modified gravity parameters for probes that are measuring the amplitude of the matter power spectrum. We explore the possibility to break the degeneracy between modified gravity and neutrino effects in the growth of structures by considering kinematic information related to either the growth rate on large scales or the virial velocities inside of collapsed structures. In order to study the degeneracy up to fully non-linear scales, we employ a suite of N-body simulations including both f(R) modified gravity and massive neutrinos. Our results indicate that velocity information provides an excellent tool to distinguish massive neutrinos from modified gravity. Models with different values of neutrino masses and modified gravity parameters possessing a comparable matter power spectrum at a given time have different growth rates. This leaves imprints in the velocity divergence, which is therefore better suited than the amplitude of density fluctuations to tell the models apart. In such models with a power spectrum comparable to ΛCDM today, the growth rate is strictly enhanced. We also find the velocity dispersion of virialised clusters to be well suited to constrain deviations from general relativity without being affected by the uncertainty in the sum of neutrino masses.

scholarly journals Clustering and redshift-space distortions in modified gravity models with massive neutrinos

2019 ◽  
Vol 488 (2) ◽  
pp. 1987-2000 ◽  
Author(s):  
Jorge Enrique García-Farieta ◽  
Federico Marulli ◽  
Alfonso Veropalumbo ◽  
Lauro Moscardini ◽  
Rigoberto A Casas-Miranda ◽  
...  
Keyword(s):  
Dark Matter ◽  
Modified Gravity ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Gravity Models ◽  
Linear Growth Rate ◽  
Λcdm Model ◽  
Point Correlation ◽  
Massive Neutrinos ◽  
Modified Gravity Models

Abstract Modified gravity and massive neutrino cosmologies are two of the most interesting scenarios that have been recently explored to account for possible observational deviations from the concordance Λ cold dark matter (ΛCDM) model. In this context, we investigated the large-scale structure of the Universe by exploiting the dustgrain-pathfinder simulations that implement, simultaneously, the effects of f(R) gravity and massive neutrinos. To study the possibility of breaking the degeneracy between these two effects, we analysed the redshift-space distortions in the clustering of dark matter haloes at different redshifts. Specifically, we focused on the monopole and quadrupole of the two-point correlation function, both in real and redshift space. The deviations with respect to ΛCDM model have been quantified in terms of the linear growth rate parameter. We found that redshift-space distortions provide a powerful probe to discriminate between ΛCDM and modified gravity models, especially at high redshifts (z ≳ 1), even in the presence of massive neutrinos.

scholarly journals Breaking degeneracies in modified gravity with higher (than 2nd) order weak-lensing statistics

2018 ◽  
Vol 619 ◽  
pp. A38 ◽  
Author(s):  
Austin Peel ◽  
Valeria Pettorino ◽  
Carlo Giocoli ◽  
Jean-Luc Starck ◽  
Marco Baldi
Keyword(s):  
Modified Gravity ◽  
Gravitational Interaction ◽  
Higher Order ◽  
Density Fluctuations ◽  
Weak Lensing ◽  
Angular Scale ◽  
The Standard Model ◽  
Universal Expansion ◽  
Massive Neutrinos ◽  
Non Gaussian

General relativity (GR) has been well tested up to solar system scales, but it is much less certain that standard gravity remains an accurate description on the largest, that is cosmological, scales. Many extensions to GR have been studied that are not yet ruled out by the data, including by that of the recent direct gravitational wave detections. Degeneracies among the standard model (ΛCDM) and modified gravity (MG) models, as well as among different MG parameters, must be addressed in order to best exploit information from current and future surveys and to unveil the nature of dark energy. We propose various higher-order statistics in the weak-lensing signal as a new set of observables able to break degeneracies between massive neutrinos and MG parameters. We have tested our methodology on so-called f(R) models, which constitute a class of viable models that can explain the accelerated universal expansion by a modification of the fundamental gravitational interaction. We have explored a range of these models that still fit current observations at the background and linear level, and we show using numerical simulations that certain models which include massive neutrinos are able to mimic ΛCDM in terms of the 3D power spectrum of matter density fluctuations. We find that depending on the redshift and angular scale of observation, non-Gaussian information accessed by higher-order weak-lensing statistics can be used to break the degeneracy between f(R) models and ΛCDM. In particular, peak counts computed in aperture mass maps outperform third- and fourth-order moments.

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