[Paper Review] Peeking into the next decade in Large-Scale Structure Cosmology with its Effective Field Theory

Diogo Bragança, Yaniv Donath+2 more|arXiv (Cornell University)|Jul 11, 2023

Cosmology and Gravitation Theories12 citations

TL;DR

The paper uses the EFTofLSS to forecast how DESI and MegaMapper can improve cosmological parameter constraints, introducing a perturbativity prior to manage loop terms and EFT parameters.

ABSTRACT

After the successful full-shape analyses of BOSS data using the Effective Field Theory of Large-Scale Structure, we investigate what upcoming galaxy surveys might achieve. We introduce a ``perturbativity prior" that ensures that loop terms are as large as theoretically expected, which is effective in the case of a large number of EFT parameters. After validating our technique by comparison with already-performed analyses of BOSS data, we provide Fisher forecasts using the one-loop prediction for power spectrum and bispectrum for two benchmark surveys: DESI and MegaMapper. We find overall great improvements on the cosmological parameters. In particular, we find that MegaMapper (DESI) should obtain at least a 12$σ$ ($2σ$) evidence for non-vanishing neutrino masses, bound the curvature $Ω_k$ to 0.0012 (0.012), and primordial inflationary non-Gaussianities as follows: $f_{ ext{NL}}^{ ext{loc.}}$ to $\pm 0.26$ (3.3), $f_{ ext{NL}}^{ ext{eq.}}$ to $\pm16$ (92), $f_{ ext{NL}}^{ ext{orth.}}$ to $\pm 4.2$ (27). Such measurements would provide much insight on the theory of Inflation. We investigate the limiting factor of shot noise and ignorance of the EFT parameters.

Motivation & Objective

• Assess what upcoming galaxy surveys can achieve with the EFTofLSS full-shape analyses.
• Introduce and test a perturbativity prior to stabilize forecasts with many EFT parameters.
• Provide Fisher forecasts for DESI and MegaMapper using one-loop power spectrum and bispectrum.
• Validate the forecasting approach against existing BOSS analyses.
• Highlight the limiting factors of shot noise and EFT parameter knowledge.

Proposed method

• Use one-loop EFTofLSS predictions for the power spectrum and bispectrum.
• Compute Fisher matrices incorporating all multipoles of the line-of-sight angle and two redshift bin sets.
• Combine redshift bins by summing Fisher matrices and accounting for redshift-dependent covariances.
• Implement three EFT-parameter knowledge scenarios: fixed, galaxy-formation prior, and perturbativity prior.
• Forecast cosmological parameters including neutrino masses, curvature, and primordial non-Gaussianities (f_NL shapes).
• Provide public code for the Fisher forecasts.

Experimental results

Research questions

• RQ1 What cosmological information can next-generation LSS surveys extract using EFTofLSS full-shape analyses?
• RQ2 How does a perturbativity prior affect forecasts with many EFT parameters?
• RQ3 What are the forecasted constraints on neutrino masses, curvature, and primordial non-Gaussianities for DESI and MegaMapper?
• RQ4 How do shot noise and EFT-parameter uncertainties limit precision?

Key findings

• DESI is forecast to constrain the sum of neutrino masses with at least 2σ evidence for nonzero masses using power spectrum and bispectrum.
• MegaMapper is forecast to achieve ≳12σ evidence for nonzero neutrino masses under the same framework.
• Omega_k can be constrained to 0.051 (DESI) and 0.0012 (MegaMapper).
• f_NL^loc, f_NL^eq, f_NL^orth can be constrained to ±3.3, ±92 (±114 without perturbativity prior), and ±27 for DESI; MegaMapper can reach ±0.26, ±16 (±18 without prior), and ±4 respectively.
• The perturbativity prior helps mitigate overestimates from many EFT parameters, with additional gains limited by shot noise and priors on EFT terms.
• Results suggest substantial improvements over Planck, particularly for neutrino masses and primordial non-Gaussianities.