DESI DR1 Lyman-alpha data yields Δ²★=0.379±0.032 and n★=-2.309±0.019 at k★=0.009 km⁻¹s and z=3, sharpening N_eff, α_s, and β_s constraints by factors of 1.18-1.90 when combined with other probes.
The cosmological simulation code GADGET-2
6 Pith papers cite this work. Polarity classification is still indexing.
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abstract
We discuss the cosmological simulation code GADGET-2, a new massively parallel TreeSPH code, capable of following a collisionless fluid with the N-body method, and an ideal gas by means of smoothed particle hydrodynamics (SPH). Our implementation of SPH manifestly conserves energy and entropy in regions free of dissipation, while allowing for fully adaptive smoothing lengths. Gravitational forces are computed with a hierarchical multipole expansion, which can optionally be applied in the form of a TreePM algorithm, where only short-range forces are computed with the `tree'-method while long-range forces are determined with Fourier techniques. Time integration is based on a quasi-symplectic scheme where long-range and short-range forces can be integrated with different timesteps. Individual and adaptive short-range timesteps may also be employed. The domain decomposition used in the parallelisation algorithm is based on a space-filling curve, resulting in high flexibility and tree force errors that do not depend on the way the domains are cut. The code is efficient in terms of memory consumption and required communication bandwidth. It has been used to compute the first cosmological N-body simulation with more than 10^10 dark matter particles, reaching a homogeneous spatial dynamic range of 10^5 per dimension in a 3D box. It has also been used to carry out very large cosmological SPH simulations that account for radiative cooling and star formation, reaching total particle numbers of more than 250 million. We present the algorithms used by the code and discuss their accuracy and performance using a number of test problems. GADGET-2 is publicly released to the research community.
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astro-ph.CO 6representative citing papers
LPT-matched integrators for cosmological simulations outperform FastPM with O(1-100) timesteps while convergence is limited to order 3/2 post-shell-crossing due to acceleration field irregularity.
Hydrodynamical simulations in f(R) gravity using Illustris-TNG find observable 20% effects on high-z HI and stellar power spectra exceeding SKA errors, plus changes in disc galaxy formation.
Analytic compression of EFT parameters for Lyα forest P1D via Fisher matrix and linearization allows efficient marginalization, saturating constraints with linear bias plus five effective terms and forecasting 10% and 2% precision on Δ²_p and n_p at k_p=0.7 Mpc^{-1}.
A new multi-scale hierarchical framework in GR uses matter horizons to extend perturbation theory beyond shell-crossing by gluing spacetimes with opposite orientation.
Novel implementation of anisotropic 3PCF model and estimator tested on 298 halo catalogs shows degeneracy breaking between f and b1 in 3PCF-only analysis but limited added value in joint 2PCF+3PCF due to tree-level model shortcomings on small scales.
citing papers explorer
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Cosmological analysis of the DESI DR1 Lyman alpha 1D power spectrum
DESI DR1 Lyman-alpha data yields Δ²★=0.379±0.032 and n★=-2.309±0.019 at k★=0.009 km⁻¹s and z=3, sharpening N_eff, α_s, and β_s constraints by factors of 1.18-1.90 when combined with other probes.
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Perturbation-theory informed integrators for cosmological simulations
LPT-matched integrators for cosmological simulations outperform FastPM with O(1-100) timesteps while convergence is limited to order 3/2 post-shell-crossing due to acceleration field irregularity.
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Realistic simulations of galaxy formation in f(R) modified gravity
Hydrodynamical simulations in f(R) gravity using Illustris-TNG find observable 20% effects on high-z HI and stellar power spectra exceeding SKA errors, plus changes in disc galaxy formation.
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Analytic compression of the effective field theory of the Lyman-alpha forest
Analytic compression of EFT parameters for Lyα forest P1D via Fisher matrix and linearization allows efficient marginalization, saturating constraints with linear bias plus five effective terms and forecasting 10% and 2% precision on Δ²_p and n_p at k_p=0.7 Mpc^{-1}.
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An essential building block for cosmological zoom-in perturbation theory
A new multi-scale hierarchical framework in GR uses matter horizons to extend perturbation theory beyond shell-crossing by gluing spacetimes with opposite orientation.
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Modeling and measuring the anisotropic halo 3-point correlation function: a coordinated study
Novel implementation of anisotropic 3PCF model and estimator tested on 298 halo catalogs shows degeneracy breaking between f and b1 in 3PCF-only analysis but limited added value in joint 2PCF+3PCF due to tree-level model shortcomings on small scales.