اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدFFT-PT: Reducing the two-loop large-scale structure power spectrum to low-dimensional radial integrals
47
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Modeling the large-scale structure of the universe on nonlinear scales has the potential to substantially increase the science return of upcoming surveys by increasing the number of modes available for model comparisons. One way to achieve this is to model nonlinear scales perturbatively. Unfortunately, this involves high-dimensional loop integrals that are cumbersome to evaluate. Trying to simplify this, we show how two-loop (next-to-next-to-leading order) corrections to the density power spectrum can be reduced to low-dimensional, radial integrals. Many of those can be evaluated with a one-dimensional Fast Fourier Transform, which is significantly faster than the five-dimensional Monte-Carlo integrals that are needed otherwise. The general idea of this FFT-PT method is to switch between Fourier and position space to avoid convolutions and integrate over orientations, leaving only radial integrals. This reformulation is independent of the underlying shape of the initial linear density power spectrum and should easily accommodate features such as those from baryonic acoustic oscillations. We also discuss how to account for halo bias and redshift space distortions.
قيم البحث
اقرأ أيضاً
Cosmological neutrinos have their greatest influence in voids: these are the regions with the highest neutrino to dark matter density ratios. The marked power spectrum can be used to emphasize low density regions over high density regions, and theref
ore is potentially much more sensitive than the power spectrum to the effects of neutrino masses. Using 22,000 N-body simulations from the Quijote suite, we quantify the information content in the marked power spectrum of the matter field, and show that it outperforms the standard power spectrum by setting constraints improved by a factor larger than 2 on all cosmological parameters. The combination of marked and standard power spectrum allows to place a 4.3{sigma} constraint on the minimum sum of the neutrino masses with a volume equal to 1 (Gpc/h)^3 and without CMB priors. Combinations of different marked power spectra yield a 6{sigma} constraint within the same conditions.
We derive a non-perturbative equation for the large scale structure power spectrum of long-wavelength modes. Thereby, we use an operator product expansion together with relations between the three-point function and power spectrum in the soft limit.
The resulting equation encodes the coupling to ultraviolet (UV) modes in two time-dependent coefficients, which may be obtained from response functions to (anisotropic) parameters, such as spatial curvature, in a modified cosmology. We argue that both depend weakly on fluctuations deep in the UV. As a byproduct, this implies that the renormalized leading order coefficient(s) in the effective field theory (EFT) of large scale structures receive most of their contribution from modes close to the non-linear scale. Consequently, the UV dependence found in explicit computations within standard perturbation theory stems mostly from counter-term(s). We confront a simplified version of our non-perturbative equation against existent numerical simulations, and find good agreement within the expected uncertainties. Our approach can in principle be used to precisely infer the relevance of the leading order EFT coefficient(s) using small volume simulations in an `anisotropic separate universe framework. Our results suggest that the importance of these coefficient(s) is a $sim 10 %$ effect, and plausibly smaller.
Published galaxy power spectra from the 2dFGRS and SDSS are not in good agreement. We revisit this issue by analyzing both the 2dFGRS and SDSS DR5 catalogues using essentially identical techniques. We confirm that the 2dFGRS exhibits relatively more
large scale power than the SDSS, or, equivalently, SDSS has more small scale power. We demonstrate that this difference is due to the r-band selected SDSS catalogue being dominated by more strongly clustered red galaxies, which have a stronger scale dependent bias. The power spectra of galaxies of the same rest frame colours from the two surveys match well. If not accounted for, the difference between the SDSS and 2dFGRS power spectra causes a bias in the obtained constraints on cosmological parameters which is larger than the uncertainty with which they are determined. We also found that the correction developed by Cole et al.(2005) to model the distortion in the shape of the power spectrum due to non-linear evolution and scale dependent bias is not able to reconcile the constraints obtained from the 2dFGRS and SDSS power spectra. Intriguingly, the model is able to describe the differences between the 2dFGRS and the much more strongly clustered LRG sample, which exhibits greater nonlinearities. This shows that more work is needed to understand the relation between the galaxy power spectrum and the linear perturbation theory prediction for the power spectrum of matter fluctuations. It is therefore important to accurately model these effects to get precise estimates of cosmological parameters from these power spectra and from future galaxy surveys like Pan-STARRS, or the Dark Energy Survey, which will use selection criteria similar to the one of SDSS.
We compute the one-loop density power spectrum including Newtonian and relativistic contributions, as well as the primordial non-Gaussianity contributions from $f_{rm NL}$ and $g_{rm NL}$ in the local configuration. To this end we take solutions to t
he Einstein equations in the long-wavelength approximation and provide expressions for the matter density perturbation at second and third order. These solutions have shown to be complementary to the usual Newtonian cosmological perturbations. We confirm a sub-dominant effect from pure relativistic terms, manifested at scales dominated by cosmic variance, but find that a sizable effect of order one comes from $g_{rm NL}$ values allowed by Planck-2018 constraints, manifested at scales probed by forthcoming galaxy surveys like DESI and Euclid. As a complement, we present the matter bispectrum at the tree-level including the mentioned contributions.
In this paper we show how effects from small scales enter the angular-redshift power spectrum $C_ell(z,z)$. In particular, we show that spectroscopic surveys with high redshift resolution are affected by small scales already on large angular scales,
i.e. at low multipoles. Therefore, when considering the angular power spectrum with spectroscopic redshift resolution, it is important to account for non-linearities relevant on small scales even at low multipoles. This may also motivate the use of the correlation function instead of the angular power spectrum. These effects, which are very relevant for bin auto-correlations, but not so important for cross-correlations, are quantified in detail.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
