我们提出Goku，一套宇宙学N体模拟，以及相应的10维仿真器GokuEmu，用于非线性物质功率谱。这些模拟覆盖了Λ冷暗物质（ΛCDM）宇宙学的基础参数及其扩展，包括动力学暗能量（$w_0$，$w_a$）、中微子质量总和（$\sum m_ν$）、中微子有效种类数（$N_\text{eff}$）以及标量谱指数跑动（$α_\text{s}$），从而能够利用来自Roman Space Telescope、Euclid和LSST等未来巡天项目的数据检验新物理。该套件在MF-Box框架内设计，该框架整合了多尺度和多保真度模拟，套件包含在$1\\,(\text{Gpc}/h)^3$体积中演化$3000^3$个粒子的高保真度模拟，以及在多种箱体尺寸下使用$750^3$个粒子的低保真度模拟。该方法在高似然区域实现百分比级精度，在更广参数范围内实现5%精度，同时与单一保真度方法相比将计算成本降低94%。模拟采用了对大质量中微子的精确处理，增强了对非线性尺度上物质功率谱的预测。关键创新包括自适应采样策略以及使用束搜索来优化泛化精度。该仿真器适用于红移$z \leq 3$和尺度$0.01 \lesssim k / (h \\, \text{Mpc}^{-1}) \lesssim 10$。除物质功率谱外，这些模拟还支持对其他统计量的分析，例如暗晕质量函数。该仿真器及其训练数据已在https://github.com/astro-YYH/GokuEmu公开提供，为宇宙学参数推断和模型检验提供了宝贵资源。
英文摘要：
We present Goku, a suite of cosmological $N$-body simulations, and the corresponding 10-dimensional emulator, GokuEmu, for the nonlinear matter power spectrum. The simulations span the base parameters of $Λ$ Cold Dark Matter ($Λ$CDM) cosmology and its extensions, including dynamical dark energy ($w_0$, $w_a$), the sum of the neutrino masses ($\sum m_ν$), the effective number of neutrinos ($N_\text{eff}$), and the running of the scalar spectral index ($α_\text{s}$), enabling tests of new physics with data from upcoming surveys like the Roman Space Telescope, Euclid, and LSST. Designed within the MF-Box framework, which integrates multi-scale and multi-fidelity simulations, the suite includes high-fidelity simulations evolving $3000^3$ particles in $1\,(\text{Gpc}/h)^3$ volumes and low-fidelity simulations with $750^3$ particles across varying box sizes. This approach achieves percent-level accuracy in high-likelihood regions and 5% accuracy across broader parameter ranges, while reducing computational costs by 94% compared to single-fidelity methods. The simulations adopt an accurate treatment of massive neutrinos, enhancing predictions of the matter power spectrum on nonlinear scales. Key innovations include an adaptive sampling strategy and the use of beam search to optimize generalization accuracy. The emulator is valid for redshifts $z \leq 3$ and scales $0.01 \lesssim k / (h \, \text{Mpc}^{-1}) \lesssim 10$. Beyond the matter power spectrum, the simulations also support analyses of other statistical measures, such as the halo mass function. The emulator and its training data are publicly available at https://github.com/astro-YYH/GokuEmu, providing a valuable resource for cosmological parameter inference and model testing.
We compare and validate COLA (COmoving Lagrangian Acceleration) simulations against existing emulators in the literature, namely Bacco and Euclid Emulator 2. Our analysis focuses on the non-linear response function, i.e., the ratio between the non-linear dark matter power spectrum in a given cosmology with respect to a pre-defined reference cosmology, which is chosen to be the Euclid Emulator 2 reference cosmology in this paper. We vary three cosmological parameters, the total matter density, the amplitude of the primordial scalar perturbations and the spectral index. By comparing the COLA non…
In this work we extend our recently developed multi-fidelity emulation technique to the simulated Lyman-$α$ forest flux power spectrum. Multi-fidelity emulation allows interpolation of simulation outputs between cosmological parameters using many cheap low-fidelity simulations and a few expensive high-fidelity simulations. Using a test suite of small box (30 Mpc/h) simulations, we show that multi-fidelity emulation is able to reproduce the Lyman-$α$ forest flux power spectrum well, achieving an average accuracy when compared to a test suite of $0.8\%$. We further show that it has a substantial…
We perform an ensemble of $N$-body simulations with $2048^3$ particles for 101 flat $w$CDM cosmological models sampled based on a maximin-distance Sliced Latin Hypercube Design. By using the halo catalogs extracted at multiple redshifts in the range of $z=[0,1.48]$, we develop Dark Emulator, which enables fast and accurate computations of the halo mass function, halo-matter cross-correlation, and halo auto-correlation as a function of halo masses, redshift, separations and cosmological models, based on the Principal Component Analysis and the Gaussian Process Regression for the large-dimension…
Design and optimization of neural networks for multifidelity cosmological emulation
University of California, Riverside（加州大学河滨分校）；Department of Physics & Astronomy, University of California, Riverside（加州大学河滨分校物理与天文系）；Department of Physics, University of Michigan（密歇根大学物理系）；Leinweber Center for Theoretical Physics（莱因韦伯理论物理中心）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
We describe our nonlinear emulation (i.e., interpolation) framework that combines the halo occupation distribution (HOD) galaxy bias model with $N$-body simulations of nonlinear structure formation, designed to accurately predict the projected clustering and galaxy-galaxy lensing signals from luminous red galaxies (LRGs) in the redshift range $0.16 < z < 0.36$ on comoving scales $0.6 < r_p < 30$ \hMpc. The interpolation accuracy is $\lesssim 1-2$ per cent across the entire physically plausible range of parameters for all scales considered. We correctly recover the true value of the cosmologica…
Scientific analyses often rely on slow, but accurate forward models for observable data conditioned on known model parameters. While various emulation schemes exist to approximate these slow calculations, these approaches are only safe if the approximations are well understood and controlled. This workshop submission reviews and updates a previously published method, which has been used in cosmological simulations, to (1) train an emulator while simultaneously estimating posterior probabilities with MCMC and (2) explicitly propagate the emulation error into errors on the posterior probabilitie…
We introduce an emulator approach to predict the non-linear matter power spectrum for broad classes of beyond-$Λ$CDM cosmologies, using only a suite of $Λ$CDM $N$-body simulations. By including a range of suitably modified initial conditions in the simulations, and rescaling the resulting emulator predictions with analytical `halo model reactions', accurate non-linear matter power spectra for general extensions to the standard $Λ$CDM model can be calculated. We optimise the emulator design by substituting the simulation suite with non-linear predictions from the standard {\sc halofit} tool. We…
We use the emulation framework CosmoPower to construct and publicly release neural network emulators of cosmological observables, including the Cosmic Microwave Background (CMB) temperature and polarization power spectra, matter power spectrum, distance-redshift relation, baryon acoustic oscillation (BAO) and redshift-space distortion (RSD) observables, and derived parameters. We train our emulators on Einstein-Boltzmann calculations obtained with high-precision numerical convergence settings, for a wide range of cosmological models including $Λ$CDM, $w$CDM, $Λ$CDM+$N_\mathrm{eff}$, and $Λ$CDM…
Gaussian-Process Emulation of the Redshift-Space Halo Power Spectrum Monopole in Cosmologies with Massive Neutrinos
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与前沿科学研究院）；Chinese Academy of Sciences South America Center for Astronomy (CASSACA), National Astronomical Observatories, Chinese Academy of Sciences（中国科学院南美天文中心）
Modern cosmological surveys are delivering datasets characterized by unprecedented quality and statistical completeness; this trend is expected to continue into 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 nonlinear 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 …
We construct an emulator for the halo mass function over group and cluster mass scales for a range of cosmologies, including the effects of dynamical dark energy and massive neutrinos. The emulator is based on the recently completed Mira-Titan Universe suite of cosmological $N$-body simulations. The main set of simulations spans 111 cosmological models with 2.1 Gpc boxes. We extract halo catalogs in the redshift range $z=[0.0, 2.0]$ and for masses $M_{200\mathrm{c}}\geq 10^{13}M_\odot/h$. The emulator covers an 8-dimensional hypercube spanned by {$Ω_\mathrm{m}h^2$, $Ω_\mathrm{b}h^2$, $Ω_νh^2$,…
We implement a model for the two-point statistics of biased tracers that combines dark matter dynamics from $N$-body simulations with an analytic Lagrangian bias expansion. Using Aemulus, a suite of $N$-body simulations built for emulation of cosmological observables, we emulate the cosmology dependence of these nonlinear spectra from redshifts $z = 0$ to $z=2$. We quantify the accuracy of our emulation procedure, which is sub-per cent at $k=1\, h {\rm Mpc}^{-1}$ for the redshifts probed by upcoming surveys and improves at higher redshifts. We demonstrate its ability to describe the statistics…
We present a suite of FIRE-2 cosmological zoom-in simulations of isolated field dwarf galaxies, all with masses of $M_\mathrm{halo} \approx 10^{10}\,$M$_\odot$ at $z=0$, across a range of dark matter models. For the first time, we compare how both self-interacting dark matter (SIDM) and/or warm dark matter (WDM) models affect the assembly histories as well as the central density structure in fully hydrodynamical simulations of dwarfs. Dwarfs with smaller stellar half-mass radii (r$_{1/2}<500$ pc) have lower $σ_\star/V_\mathrm{max}$ ratios, reinforcing the idea that smaller dwarfs may reside in…
We present MGLenS, a large series of modified gravity lensing simulations tailored for cosmic shear data analyses and forecasts in which cosmological and modified gravity parameters are varied simultaneously. Based on the FORGE and BRIDGE $N$-body simulation suites presented in companion papers, we construct 500,000 deg$^2$ of mock Stage-IV lensing data, sampling a pair of 4-dimensional volumes designed for the training of emulators. We validate the accuracy of MGLenS with inference analyses based on the lensing power spectrum exploiting our implementation of $f(R)$ and nDGP theoretical predic…
Strong gravitational lensing observations can test structure formation models by constraining the masses and concentrations of subhaloes in massive galaxy clusters. Recent work has concluded that cluster subhaloes are more abundant and/or concentrated than predicted by $Λ$CDM simulations; this finding has been interpreted as arising from unidentified issues with simulations or an incorrect understanding of the nature of dark matter. We test these hypotheses by comparing observed subhalo masses and maximum circular velocities $v_\mathrm{max}$ to predictions from the high resolution Hydrangea ga…
Modeling nonlinear scales for dynamical dark energy cosmologies with COLA
CBPF - Brazilian Center for Research in Physics（巴西物理研究中心）；Instituto de Física Teórica da Universidade Estadual Paulista（圣保罗州立大学理论物理研究所）；Department of Physics & Astronomy, Stony Brook University（石溪大学物理与天文学系）；C. N. Yang Institute for Theoretical Physics, Stony Brook University（石溪大学陈省身理论物理研究所）
CMBolic: Symbolic emulators for the Cosmic Microwave Background. I. Lensing
CEICO, Institute of Physics of the Czech Academy of Sciences（捷克科学院物理研究所）；Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University（查理大学数学物理学院理论物理研究所）；Astrophysics, University of Oxford（牛津大学天体物理学系）；Institute of Cosmology & Gravitation, University of Portsmouth（朴茨茅斯大学宇宙学与引力研究所）
We present a public data release of halo catalogs from a suite of 125 cosmological $N$-body simulations from the Abacus project. The simulations span 40 $w$CDM cosmologies centered on the Planck 2015 cosmology at two mass resolutions, $4\times 10^{10}\;h^{-1}M_\odot$ and $1\times 10^{10}\;h^{-1}M_\odot$, in $1.1\;h^{-1}\mathrm{Gpc}$ and $720\;h^{-1}\mathrm{Mpc}$ boxes, respectively. The boxes are phase-matched to suppress sample variance and isolate cosmology dependence. Additional volume is available via 16 boxes of fixed cosmology and varied phase; a few boxes of single-parameter excursions …
Providing accurate predictions for the spatial distribution of matter and luminous tracers in the presence of massive neutrinos is an important task, given the imminent arrival of highly accurate large-scale structure observations. In this work, we address this challenge by extending cosmology-rescaling algorithms to massive neutrino cosmologies. In this way, a $Λ$CDM simulation can be modified to provide nonlinear structure formation predictions in the presence a hot component of arbitrary mass, and, if desired, to include non-gravitational modifications to the clustering of matter on large s…
Small scale clustering of late forming dark matter
我们对后期形成的暗物质（LFDM）场景中物质的非线性聚集进行了研究，其中暗物质是由非最小耦合的标量场从辐射到无碰撞物质的转变产生的。该模型的一个显著特点是在小尺度下线性物质功率谱中存在阻尼振荡截止。我们使用一套高分辨率的N体模拟来研究LFDM在非线性物质功率谱、晕质量和速度函数以及晕密度分布上的印记。该模型在很大程度上满足高红移物质的功率谱限制莱曼- $α$森林测量，而它预测抑制丰度的低质量晕（$\sim 10^{9}-10^{10}$ h $^{-1}$ M $_\odot$）在所有的红移相比，香草$Λ$ CDM模型。对LFDM晕速度函数的分析表明，与$Λ$ CDM预测相比，LFDM晕速度函数与观测到的低速星系在局部体积中的丰度更接近。质量为$M\gtrsim 10^{11}$ h $^{-1}$ M $_\odot$的晕显示出密度分布与$Λ$ CDM预期值的微小偏差，而质量较小的晕密度较低，这与它们比$Λ$ CDM对应物晚形成的事实相一致。
Integrated Sachs-Wolfe maps from the Gower Street $w$CDM simulations
MTA–CSFK Lendület “Momentum” Large-Scale Structure (LSS) Research Group（MTA-CSFK 引力波“动量”大尺度结构研究组）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与教育网络天文学与地球科学研究中心）；Institute of Physics and Astronomy, ELTE Eötvös Loránd University（罗兰大学物理与天文学研究所）；Institute for Astronomy, University of Hawaii（夏威夷大学天文学研究所）
本文通过扩展pyGenISW包，利用Gower Street N-body模拟生成791个wCDM宇宙模型的全天空ISW地图，验证了ISW信号在不同暗能量参数空间中的可靠性。
We present a full forward-modeled $w$CDM analysis of the KiDS-1000 weak lensing maps using graph-convolutional neural networks (GCNN). Utilizing the $\texttt{CosmoGrid}$, a novel massive simulation suite spanning six different cosmological parameters, we generate almost one million tomographic mock surveys on the sphere. Due to the large data set size and survey area, we perform a spherical analysis while limiting our map resolution to $\texttt{HEALPix}$ $n_\mathrm{side}=512$. We marginalize over systematics such as photometric redshift errors, multiplicative calibration and additive shear bia…
We study the impact of a warm dark matter (WDM) cosmology on dwarf galaxy formation through a suite of cosmological hydrodynamical zoom-in simulations of $M_{\rm halo} \approx10^{10}\,M_{\odot}$ dark matter halos as part of the Feedback in Realistic Environments (FIRE) project. A main focus of this paper is to evaluate the combined effects of dark matter physics and stellar feedback on the well-known small-scale issues found in cold dark matter (CDM) models. We find that the $z=0$ stellar mass of a galaxy is strongly correlated with the central density of its host dark matter halo at the time …
We perform the first test of dark matter (DM) stress-energy evolution through cosmic history, using cosmic microwave background measurements supplemented with baryon acoustic oscillation data and the Hubble Space Telescope key project data. We constrain the DM equation of state (EoS) in 8 redshift bins, and its sound speed and (shear) viscosity in 9 redshift bins, finding no convincing evidence for non-$Λ$CDM values in any of the redshift bins. Despite this enlarged parameter space, the sound speed and viscosity are constrained relatively well at late times (due to the inclusion of CMB lensing…
We present a new, updated version of the EuclidEmulator (called EuclidEmulator2), a fast and accurate predictor for the nonlinear correction of the matter power spectrum. Percent-level accurate emulation is now supported in the eight-dimensional parameter space of $w_0w_a$CDM$+\sum m_ν$models between redshift $z=0$ and $z=3$ for spatial scales within the range 0.01 $h$/Mpc $\leq k \leq$ 10 $h$/Mpc. In order to achieve this level of accuracy, we have had to improve the quality of the underlying N-body simulations used as training data: (1) we use self-consistent linear evolution of non-dark mat…
Accurate predictions for the non-linear matter power spectrum are needed to confront theory with observations in current and near future weak lensing and galaxy clustering surveys. We propose a computationally cheap method to create an emulator for modified gravity models by utilizing existing emulators for $Λ$CDM. Using a suite of $N$-body simulations we construct a fitting function for the enhancement of both the linear and non-linear matter power spectrum in the commonly studied Hu-Sawicki $f(R)$ gravity model valid for wave-numbers $k \lesssim 5-10\, h\text{Mpc}^{-1}$ and redshifts $z \les…
Modifying $Λ$CDM dynamics via out-of-equilibrium axions: reconciling SH0ES and DESI $H_0$ values
Nuclear Department, ENEA - C. R. Frascati（意大利国家新能源与可再生能源公司弗拉斯卡蒂研究中心核物理部）；Physics Department, “Sapienza” University of Rome（罗马大学物理系）；Department of Physics, Istanbul Technical University（伊斯坦布尔理工大学物理系）
Ten-dimensional neural network emulator for the nonlinear matter power spectrum
Department of Physics & Astronomy, University of California, Riverside（加州大学河滨分校物理与天文系）；Department of Physics, University of Michigan（密歇根大学物理系）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
We present here the cosmo-SLICS, a new suite of simulations specially designed for the analysis of current and upcoming weak lensing data beyond the standard two-point cosmic shear. We sample the $[Ω_{\rm m}, σ_8, h, w_0]$ parameter space at 25 points organised in a Latin hyper-cube, spanning a range that contains most of the $2σ$ posterior distribution from ongoing lensing surveys. At each of these nodes we evolve a pair of $N$-body simulations in which the sampling variance is highly suppressed, and ray-trace the volumes 800 times to further increase the effective sky coverage. We extract a …
