A test suite for quantitative comparison of hydrodynamic codes in astrophysics

Tasker, Elizabeth J.; Brunino, Riccardo; Mitchell, N. L.; Michielsen, D.; Hopton, Stephen; Pearce, Frazer R.; Bryan, Greg L.; Theuns, Tom

doi:10.1111/j.1365-2966.2008.13836.x

Cited by 150 publications

(175 citation statements)

References 33 publications

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“…Constructing adequate models for these effects, including them all in simulations, and correctly determining their relative contributions to the overall structure formation process, is a highly non-trivial process. Indeed, various code comparison projects over the years [298,299,300,301,302] have shown disagreement between codes on the order of tens of percent, and comparison with observations [e.g. 290] suggests that baryon-inclusive simulations are only good at the 10% accuracy level so far.…”

Section: Simulating the Universementioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

459

210

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Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, ΛCDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of ΛCDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.Keywords: cosmology -dark energy -cosmological constant problem -modified gravitydark matter -early universe Cosmology has been both blessed and cursed by the establishment of a standard model: ΛCDM. On the one hand, the model has turned out to be extremely predictive, explanatory, and observationally robust, providing us with a substantial understanding of the formation of large-scale structure, the state of the early Universe, and the cosmic abundance of different types of matter and energy. It has also survived an impressive battery of precision observational tests -anomalies are few and far between, and their significance is contentious where they do arise -and its predictions are continually being vindicated through the discovery of new effects (B-mode polarization [1] and lensing [2,3] of the cosmic microwave background (CMB), and the kinetic Sunyaev-Zel'dovich effect [4] being some recent examples). These are the hallmarks of a good and valuable physical theory.On the other hand, the model suffers from profound theoretical difficulties. The two largest contributions to the energy content at late times -cold dark matter (CDM) and the cosmological constant (Λ) -have entirely mysterious physical origins. CDM has so far evaded direct detection by laboratory experiments, and so the particle field responsible for it -presumably a manifestation of "beyond the standard model" particle physics -is unknown. Curious discrepancies also appear to exist between the predicted clustering properties of CDM on small scales and observations. The cosmological constant is even more puzzling, giving rise to quite simply the biggest problem in all of fundamental physics: the question of why Λ appears to take such an unnatural value [5,6,7]. Inflation, the theory of the very early Universe, has also been criticized for being fine-tuned and under-predictive [8], and appears to leave many problems either unsolved or fundamentally unresolvable. These problems are indicative of a crisis.From January 14th-17th 2015, we held a conference in Oslo, Norway to surve...

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Section: Simulating the Universementioning

confidence: 99%

BeyondΛCDM: Problems, solutions, and the road ahead

Bull

Akrami

Adamek

et al. 2016

Physics of the Dark Universe

459

210

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“…However, comparisons between the results produced by AMR and SPH codes in a number of test cases reveal several differences (Frenk et al 1999;O'Shea et al 2005b;Agertz et al 2007;Wadsley et al 2008;Tasker et al 2008;Mitchell et al 2009). Agertz et al (2007) showed that the formation of fluid instabilities is artificially suppressed in SPH codes compared to AMR codes because of the difficulties of SPH codes in properly modeling the large density gradients that develop at the fluid interfaces.…”

Section: Introductionmentioning

confidence: 99%

The impact of numerical viscosity in SPH simulations of galaxy clusters

Valdarnini

2011

A&A

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The goal of this paper is to investigate in N-body/SPH hydrodynamical cluster simulations the impact of artificial viscosity on the ICM thermal and velocity field statistical properties. To properly reduce the effects of artificial viscosity, a time-dependent artificial viscosity scheme is implemented in an SPH code in which each particle has its own viscosity parameter, whose time evolution is governed by the local shock conditions. The new SPH code is verified in a number of test problems with known analytical or numerical reference solutions and is then used to construct a large set of N-body/SPH hydrodynamical cluster simulations. These simulations are designed to study in SPH simulations the impact of artificial viscosity on the thermodynamics of the ICM and its velocity field statistical properties by comparing results extracted at the present epoch from runs with different artificial viscosity parameters, cluster dynamical states, numerical resolution, and physical modeling of the gas. Spectral properties of the gas velocity field are investigated by measuring the velocity power spectrum E(k) for the simulated clusters. Over a limited range, the longitudinal component E c (k) exhibits a Kolgomorov-like scaling ∝k −5/3 , whilst the solenoidal power spectrum component E s (k) is strongly influenced by numerical resolution effects. The dependence of the spectra E(k) on dissipative effects is found to be significant at length scales < ∼ 100−300 kpc, with viscous damping of the velocities being less pronounced in the runs with the lowest artificial viscosity. The turbulent energy density radial profile E turb (r) is strongly affected by the numerical viscosity scheme adopted in the simulations, with the turbulent-to-total energy density ratios being higher in the runs with the lowest artificial viscosity settings and lying in the range between a few percent and ∼10%. These values are in accord with the corresponding ratios extracted from previous cluster simulations based on mesh-based codes. The radial entropy profiles show a weak dependence on the artificial viscosity parameters of the simulations, with a small amount of entropy mixing being present in cluster cores. At large cluster radii, the mass correction terms to the hydrostatic equilibrium equation are affected little by the numerical viscosity of the simulations, indicating that the X-ray mass bias is already accurately estimated in standard SPH simulations. The results presented here indicate that in individual SPH cluster simulations at least N > ∼ 256 3 gas particles are necessary to provide a correct description of turbulent spectral properties over a decade in wavenumbers, whilst radial profiles of thermodynamic variables can be reliably obtained using N > ∼ 64 3 particles. Finally, simulations in which the gas can cool radiatively are characterized by the presence in the cluster inner regions of high levels of turbulence, generated by the interaction of the compact cool gas core with the ambient medium. These findings strongly support t...

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“…This is intimately connected with the outstanding problem of star formation: as star formation transforms the ISM, adding heavy elements and kinetic energy, it determines the structure and evolution of galaxies. While modern cosmological theories can predict the distribution of dark matter in the Universe quite well, predicting the distribution of stars and gas in galaxies is still extremely difficult (Tasker et al 2008;Putman et al 2009;Tonnesen & Bryan 2009). The reason for this is the complex and dynamic ISM: simulations reach a bottleneck on scale sizes where a detailed understanding of star formation, its feedback, and the interaction between galactic disks and halos needs to be included (Stanimirović 2010).…”

Section: Galaxy Evolution Begins At Homementioning

confidence: 99%

GASKAP—The Galactic ASKAP Survey

Dickey

McClure-Griffiths

Gibson

et al. 2013

Publ. Astron. Soc. Aust.

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A survey of the Milky Way disk and the Magellanic System at the wavelengths of the 21-cm atomic hydrogen (H i) line and three 18-cm lines of the OH molecule will be carried out with the Australian Square Kilometre Array Pathfinder * Hubble Fellow. telescope. The survey will study the distribution of H i emission and absorption with unprecedented angular and velocity resolution, as well as molecular line thermal emission, absorption, and maser lines. The area to be covered includes the Galactic plane (|b| < 10°) at all declinations south of δ = +40 • , spanning longitudes 167 • through 360 • to 79 • at b = 0 • , plus the entire area of the Magellanic Stream and Clouds, a total of 13 020 deg 2 . The brightness temperature sensitivity will be very good, typically σ T 1 K at resolution 30 arcsec and 1 km s −1 . The survey has a wide spectrum of scientific goals, from studies of galaxy evolution to star formation, with particular contributions to understanding stellar wind kinematics, the thermal phases of the interstellar medium, the interaction between gas in the disk and halo, and the dynamical and thermal states of gas at various positions along the Magellanic Stream.

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A test suite for quantitative comparison of hydrodynamic codes in astrophysics

Cited by 150 publications

References 33 publications

BeyondΛCDM: Problems, solutions, and the road ahead

BeyondΛCDM: Problems, solutions, and the road ahead

The impact of numerical viscosity in SPH simulations of galaxy clusters

GASKAP—The Galactic ASKAP Survey

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