Search

Cosmology is poised to measure the neutrino mass sum M ν and has identified several smaller-scale observables sensitive to neutrinos, necessitating accurate predictions of neutrino clustering over a wide range of length scales. The FlowsForTheMasses non-linear perturbation theory for the the massive neutrino power spectrum, |$\Delta ^2_\nu (k)$|⁠ , agrees with its companion N -body simulation at the |$10~{{\ \rm per\ cent}}-15~{{\ \rm per\ cent}}$| level for k ≤ 1  h  Mpc−1. Building upon the Mira-Titan IV emulator for the cold matter, we use FlowsForTheMasses to construct an emulator for |$\Delta ^2_\nu (k)$|⁠ , Cosmic-Eν , which covers a large range of cosmological parameters and neutrino fractions Ων, 0 h 2 ≤ 0.01 (M ν ≤ 0.93 eV). Consistent with FlowsForTheMasses at the 3.5 per cent level, it returns a power spectrum in milliseconds. Ranking the neutrinos by initial momenta, we also emulate the power spectra of momentum deciles, providing information about their perturbed distribution function. Comparing a M ν = 0.15 eV model to a wide range of N -body simulation methods, we find agreement to 3 per cent for k ≤ 3 k FS = 0.17  h  Mpc−1 and to 19 per cent for k ≤ 0.4  h  Mpc−1. We find that the enhancement factor, the ratio of |$\Delta ^2_\nu (k)$| to its linear-response equivalent, is most strongly correlated with Ων, 0 h 2, and also with the clustering amplitude σ8. Furthermore, non-linearities enhance the free-streaming-limit scaling |$\partial \log (\Delta ^2_\nu /\Delta ^2_{\rm m}) / \partial \log (M_\nu)$| beyond its linear value of 4, increasing the M ν-sensitivity of the small-scale neutrino density. [ABSTRACT FROM AUTHOR]

Weak lensing of the cosmic microwave background is rapidly emerging as a powerful probe of neutrinos, dark energy, and new physics. We present a fast computation of the non-linear CMB lensing power spectrum that combines non-linear perturbation theory at early times with power spectrum emulation using cosmological simulations at late times. Comparing our calculation with light-cones from the FLAMINGO 5.6 Gpc cube dark-matter-only simulation, we confirm its accuracy to |$1{{\ \rm per\ cent}}$| (⁠|$2{{\ \rm per\ cent}}$|⁠) up to multipoles L  = 3000 (L  = 5000) for a νΛCDM cosmology consistent with current data. Clustering suppression due to small-scale baryonic phenomena such as feedback from active galactic nuclei can reduce the lensing power by |$\sim 10{{\ \rm per\ cent}}$|⁠. To our perturbation theory and emulator-based calculation, we add SP(k) , a new fitting function for this suppression, and confirm its accuracy compared to the FLAMINGO hydrodynamic simulations to |$4{{\ \rm per\ cent}}$| at L  = 5000, with similar accuracy for massive neutrino models. We further demonstrate that scale-dependent suppression due to neutrinos and baryons approximately factorize, implying that a careful treatment of baryonic feedback can limit biasing neutrino mass constraints. [ABSTRACT FROM AUTHOR]

The symmetron scalar field is a matter-coupled dark energy candidate which effectively decouples from matter in high-density regions through a symmetry restoration. We consider a previously unexplored regime, in which the vacuum mass μ ~ 2.4×10-3 eV of the symmetron is near the dark energy scale, and the matter coupling parameter M ~ 1 TeV is just beyond standard model energies. Such a field will give rise to a fifth force at submillimeter distances which can be probed by short-range gravity experiments. We show that a torsion pendulum experiment such as Eöt-Wash can exclude symmetrons in this regime for all self-couplings λ 7.5. [ABSTRACT FROM AUTHOR]

Chameleon scalar fields are dark-energy candidates which suppress fifth forces in high density regions of the Universe by becoming massive. We consider chameleon models as effective field theories and estimate quantum corrections to their potentials. Requiring that quantum corrections be small, so as to allow reliable predictions of fifth forces, leads to an upper bound m < 0.0073(ρ/10 gcm-3)1/3eV for gravitational-strength coupling whereas fifth force experiments place a lower bound of m > 0.0042 eV. An improvement of less than a factor of two in the range of fifth force experiments could test all classical chameleon field theories whose quantum corrections are well controlled and couple to matter with nearly gravitational strength regardless of the specific form of the chameleon potential. [ABSTRACT FROM AUTHOR]

We report on the design and results of the GammeV search for axion-like particles and for chameleon particles. We also discuss plans for an improved experiment to search for chameleon particles, one which is sensitive to both cosmological and power-law chameleon models. Plans for an improved axion-like particle search using coupled resonant cavities are also presented. This experiment will be more sensitive to axion-like particles than stellar astrophysical models or current helioscope experiments. [ABSTRACT FROM AUTHOR]

A number of recent studies have found evidence for a tension between observations of large-scale structure (LSS) and the predictions of the standard model of cosmology with the cosmological parameters fit to the cosmic microwave background (CMB). The origin of this ' S 8 tension' remains unclear, but possibilities include new physics beyond the standard model, unaccounted for systematic errors in the observational measurements and/or uncertainties in the role that baryons play. Here, we carefully examine the latter possibility using the new FLAMINGO suite of large-volume cosmological hydrodynamical simulations. We project the simulations onto observable harmonic space and compare with observational measurements of the power and cross-power spectra of cosmic shear, CMB lensing, and the thermal Sunyaev-Zel'dovich (tSZ) effect. We explore the dependence of the predictions on box size and resolution and cosmological parameters, including the neutrino mass, and the efficiency and nature of baryonic 'feedback'. Despite the wide range of astrophysical behaviours simulated, we find that baryonic effects are not sufficiently large to remove the S 8 tension. Consistent with recent studies, we find the CMB lensing power spectrum is in excellent agreement with the standard model, while the cosmic shear power spectrum, tSZ effect power spectrum, and the cross-spectra between shear, CMB lensing, and the tSZ effect are all in varying degrees of tension with the CMB-specified standard model. These results suggest that some mechanism is required to slow the growth of fluctuations at late times and/or on non-linear scales, but that it is unlikely that baryon physics is driving this modification. [ABSTRACT FROM AUTHOR]

Upcoming large-scale structure surveys will measure the matter power spectrum to approximately per cent level accuracy with the aim of searching for evidence for new physics beyond the standard model of cosmology. In order to avoid biasing our conclusions, the theoretical predictions need to be at least as accurate as the measurements for a given choice of cosmological parameters. However, recent theoretical work has shown that complex physical processes associated with galaxy formation (particularly energetic feedback processes associated with stars and especially supermassive black holes) can alter the predictions by many times larger than the required accuracy. Here we present SP(k) , a model for the effects of baryon physics on the non-linear matter power spectrum based on a new large suite of hydrodynamical simulations. Specifically, the ANTILLES suite consists of 400 simulations spanning a very wide range of the 'feedback landscape' and show that the effects of baryons on the matter power spectrum can be understood at approaching the per cent level in terms of the mean baryon fraction of haloes, at scales of up to |$k \, {\lesssim } \, 10\, h$| Mpc−1 and redshifts up to z  = 3. For the range of scales and redshifts that will be probed by forthcoming cosmic shear measurements, most of the effects are driven by galaxy group mass haloes (M ∼ 1013–14 M⊙). We present a simple python implementation of our model, available at https://github.com/jemme07/pyspk , which can be used to incorporate baryon effects in standard gravity-only predictions, allowing for marginalization over baryon physics within cosmological pipelines. [ABSTRACT FROM AUTHOR]

Modern cosmological surveys are delivering data sets characterized by unprecedented quality and statistical completeness; this trend is expected to continue in the future as new ground- and space-based surveys come online. In order to maximally extract cosmological information from these observations, matching theoretical predictions are needed. At low redshifts, the surveys probe the non-linear regime of structure formation where cosmological simulations are the primary means of obtaining the required information. The computational cost of sufficiently resolved large-volume simulations makes it prohibitive to run very large ensembles. Nevertheless, precision emulators built on a tractable number of high-quality simulations can be used to build very fast prediction schemes to enable a variety of cosmological inference studies. We have recently introduced the Mira–Titan Universe simulation suite designed to construct emulators for a range of cosmological probes. This gravity-only set of simulations covers the standard six cosmological parameters {ωm, ωb, σ8, h ,  n s, w 0} and, in addition, includes massive neutrinos and a dynamical dark energy equation of state {ων, w a}. In this paper, we present the final emulator for the matter power spectrum based on 111 cosmological simulations, each covering a (2.1 Gpc)3 volume and evolving 32003 particles. An additional set of 1776 lower resolution simulations and TimeRG perturbation theory results for the power spectrum are used to cover scales straddling the linear to mildly non-linear regimes (maximum wavenumber k  = 5 Mpc−1). The emulator provides predictions at the 2–3 per cent level of accuracy over a wide range of cosmological parameters and is publicly released as part of this paper. [ABSTRACT FROM AUTHOR]