An emulator-based halo model in modified gravity -- I. The halo concentration-mass relation and density profile

Ruan, Cheng-Zong; Cuesta-Lazaro, Carolina; Eggemeier, Alexander; Li, Baojiu; Baugh, Carlton M.; Arnold, Christian; Bose, Sownak; Hernández-Aguayo, César; Zarrouk, Pauline; Davies, Christopher T.

doi:10.48550/arxiv.2301.02970

Cited by 2 publications

(3 citation statements)

References 103 publications

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“…We need to appreciate that another promising solution for analytical modeling of the MG PS is via the fast and reliable emulation techniques [e. g 30, 110, 111].For MG models, emulators have been proposed in e.g. [112][113][114][115][116]. This approach is sophisticated and promising, however, is still in its infancy, and has limitations.…”

Section: Discussionmentioning

confidence: 99%

Improved analytical modeling of the non-linear power spectrum in modified gravity cosmologies

Gupta¹,

Hellwing²,

Bilicki³

2023

Preprint

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Reliable analytical modeling of the non-linear power spectrum (PS) of matter perturbations is among the chief pre-requisites for cosmological analyses from the largest sky surveys. This is especially true for the models that extend the standard general-relativity paradigm by adding the fifth force, where numerical simulations can be prohibitively expensive. Here we present a method for building accurate PS models for two modified gravity (MG) variants: namely the Hu-Sawicki f (R), and the normal branch of the Dvali-Gabadadze-Porrati (nDGP) braneworld. We start by modifying the standard halo model (HM) with respect to the baseline Lambda-Cold-Dark-Matter (ΛCDM) scenario, by using the HM components with specific MG extensions. We find that our P (k)HM retains 5% accuracy only up to mildly non-linear scales (k 0.3 h/ Mpc) when compared to PS from numerical simulations. At the same time, our HM prescription much more accurately captures the ratio Υ(k) = P (k)MG/P (k)ΛCDM up to non-linear scales. We show that using HM-derived Υ(k) together with a viable non-linear ΛCDM P (k) prescription (such as halofit), we render a much better and more accurate PS predictions in MG. The new approach yields considerably improved performance, with modeled P (k)MG being now accurate to within 5% all the way to non-linear scales of k 2.5 − 3 h/ Mpc. The magnitude of deviations from GR as fostered by these MG models is typically O(10%) in these regimes. Therefore reaching 5% PS modeling is enough for forecasting constraints on modern-era cosmological observables.

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Section: Discussionmentioning

confidence: 99%

Improved analytical modeling of the non-linear power spectrum in modified gravity cosmologies

Gupta¹,

Hellwing²,

Bilicki³

2023

Preprint

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“…Current MG simulations [8,9] usually take from a factor of 2 up to a factor of 10 longer than a ΛCDM one, and performing a full MCMC parameter estimation with simulations simply becomes not a feasible task, as one would need an order of 10 4 simulations, or even more, to successfully sample the parameter space and reach convergence on the chains. Therefore, emulation techniques have been put forward in the community as viable alternatives to bypass this issue in standard cosmologies , as well as in cosmologies beyond-ΛCDM [32][33][34][35][36][37]. In order to train machine learning algorithms to be used for the emulation, we still need to create a large enough training, testing and validation simulation sets, however, the total number of simulations required for these are reduced by at least two orders of magnitude, where one would need around O(10 2 ) simulations to be divided into the specified sets.…”

Section: Introductionmentioning

confidence: 99%

“…Using equations (C.26), (C.29a) and (C.29b) we findd κG eff S κG eff F S (2) i,i (q, T ) (k, ) × I (k, T ) , (C 37). whereI (k, T ) = d 3 k 1 d 3 k 2 (2π) 3 δ D (k − k 12 )…”

mentioning

confidence: 99%

Revisiting Vainshtein screening for fast N-body simulations

Brando

Koyama

Winther

2023

J. Cosmol. Astropart. Phys.

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We revisit a method to incorporate the Vainshtein screening mechanism in N-body simulations proposed by R. Scoccimarro in [1]. We further extend this method to cover a subset of Horndeski theories that evade the bound on the speed of gravitational waves set by the binary neutron star merger GW170817. The procedure consists of the computation of an effective gravitational coupling that is time and scale dependent, G eff (k,z), where the scale dependence will incorporate the screening of the fifth-force. This is a fast procedure that when contrasted to the alternative of solving the full equation of motion for the scalar field inside N-body codes, reduces considerably the computational time and complexity required to run simulations. To test the validity of this approach in the non-linear regime, we have implemented it in a COmoving Lagrangian Approximation (COLA) N-body code, and ran simulations for two gravity models that have full N-body simulation outputs available in the literature, nDGP and Cubic Galileon. We validate the combination of the COLA method with this implementation of the Vainshtein mechanism with full N-body simulations for predicting the boost function: the ratio between the modified gravity non-linear matter power spectrum and its General Relativity counterpart. This quantity is of great importance for building emulators in beyond-ΛCDM models, and we find that the method described in this work has an agreement of below 2% for scales down to k ≈ 3h/Mpc with respect to full N-body simulations.

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An emulator-based halo model in modified gravity -- I. The halo concentration-mass relation and density profile

Cited by 2 publications

References 103 publications

Improved analytical modeling of the non-linear power spectrum in modified gravity cosmologies

Improved analytical modeling of the non-linear power spectrum in modified gravity cosmologies

Revisiting Vainshtein screening for fast N-body simulations

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