Speeding up N -body simulations of modified gravity: chameleon screening models

Journal Article · Wed Feb 01 04:00:00 EST 2017 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2017/02/050· OSTI ID:22680005

Bose, Sownak; Li, Baojiu; He, Jian-hua; Llinares, Claudio ^[1]; Barreira, Alexandre ^[2]; Hellwing, Wojciech A.; Koyama, Kazuya ^[3]; Zhao, Gong-Bo ^[4]

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1. Institute for Computational Cosmology, Department of Physics, Durham University, Durham DH1 3LE (United Kingdom)
2. Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany)
3. Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom)
4. National Astronomy Observatories, Chinese Academy of Science, Beijing, 100012 (China)

We describe and demonstrate the potential of a new and very efficient method for simulating certain classes of modified gravity theories, such as the widely studied f ( R ) gravity models. High resolution simulations for such models are currently very slow due to the highly nonlinear partial differential equation that needs to be solved exactly to predict the modified gravitational force. This nonlinearity is partly inherent, but is also exacerbated by the specific numerical algorithm used, which employs a variable redefinition to prevent numerical instabilities. The standard Newton-Gauss-Seidel iterative method used to tackle this problem has a poor convergence rate. Our new method not only avoids this, but also allows the discretised equation to be written in a form that is analytically solvable. We show that this new method greatly improves the performance and efficiency of f ( R ) simulations. For example, a test simulation with 512{sup 3} particles in a box of size 512 Mpc/ h is now 5 times faster than before, while a Millennium-resolution simulation for f ( R ) gravity is estimated to be more than 20 times faster than with the old method. Our new implementation will be particularly useful for running very high resolution, large-sized simulations which, to date, are only possible for the standard model, and also makes it feasible to run large numbers of lower resolution simulations for covariance analyses. We hope that the method will bring us to a new era for precision cosmological tests of gravity.

• OSTI ID: 22680005
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 02 Vol. 2017; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALGORITHMS
COMPUTERIZED SIMULATION
CONVERGENCE
EFFICIENCY
GRAVITATION
INSTABILITY
ITERATIVE METHODS
NONLINEAR PROBLEMS
PARTIAL DIFFERENTIAL EQUATIONS
PERFORMANCE
RESOLUTION
STANDARD MODEL
VELOCITY