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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2601.07425 |
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| _version_ | 1866917196056231936 |
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| author | Wang, Long Hernandez, David M. Zheng, Zepeng Huang, Wanhao |
| author_facet | Wang, Long Hernandez, David M. Zheng, Zepeng Huang, Wanhao |
| contents | The P$^3$T scheme is a hybrid method for simulating gravitational $N$-body systems. It combines a fast particle-tree (PT) algorithm for long-range forces with a high-accuracy particle-particle (PP, direct $N$-body) solver for short-range interactions. Preserving both PT efficiency and PP accuracy requires a robust PT-PP switching criterion. We introduce a simple free-fall-based switching criterion for general stellar systems, alongside the commonly used velocity-dispersion-based ($σ$-based) criterion. Using the \textsc{petar} code with the P$^3$T scheme and slow-down algorithmic regularization for binaries and higher-order multiples, we perform extensive simulations of star clusters to evaluate how each criterion affects energy conservation and binary evolution. For systems in virial equilibrium, we find that the free-fall-based criterion is generally more accurate for low-$σ$ or loose clusters containing binaries, whereas the $σ$-based criterion is better suited for high-$σ$ systems. Under subvirial or fractal initial conditions, both criteria struggle to maintain high energy conservation; however, the free-fall-based criterion improves as the tree timestep is reduced, whereas the $σ$-based degrades due to its low-accuracy treatment of two-body encounters. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_07425 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | A free-fall-based switching criterion for P^3 T N-body methods in collisional stellar systems Wang, Long Hernandez, David M. Zheng, Zepeng Huang, Wanhao Instrumentation and Methods for Astrophysics The P$^3$T scheme is a hybrid method for simulating gravitational $N$-body systems. It combines a fast particle-tree (PT) algorithm for long-range forces with a high-accuracy particle-particle (PP, direct $N$-body) solver for short-range interactions. Preserving both PT efficiency and PP accuracy requires a robust PT-PP switching criterion. We introduce a simple free-fall-based switching criterion for general stellar systems, alongside the commonly used velocity-dispersion-based ($σ$-based) criterion. Using the \textsc{petar} code with the P$^3$T scheme and slow-down algorithmic regularization for binaries and higher-order multiples, we perform extensive simulations of star clusters to evaluate how each criterion affects energy conservation and binary evolution. For systems in virial equilibrium, we find that the free-fall-based criterion is generally more accurate for low-$σ$ or loose clusters containing binaries, whereas the $σ$-based criterion is better suited for high-$σ$ systems. Under subvirial or fractal initial conditions, both criteria struggle to maintain high energy conservation; however, the free-fall-based criterion improves as the tree timestep is reduced, whereas the $σ$-based degrades due to its low-accuracy treatment of two-body encounters. |
| title | A free-fall-based switching criterion for P^3 T N-body methods in collisional stellar systems |
| topic | Instrumentation and Methods for Astrophysics |
| url | https://arxiv.org/abs/2601.07425 |