Discrete diffusion Lyman-alpha radiative transfer. Smith, A., Tsang, B. T., Bromm, V., & Milosavljevic, M. ArXiv e-prints, 1709:arXiv:1709.10187, September, 2017.
Discrete diffusion Lyman-alpha radiative transfer [link]Paper  abstract   bibtex   
Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Ly\${\textbackslash}alpha\$ radiative transfer in arbitrary geometries. The standard MCRT encounters a significant efficiency barrier in the high optical depth, diffusion regime. Multiple acceleration schemes have been developed to improve the efficiency of MCRT but the noise from photon packet discretization remains a challenge. The discrete diffusion Monte Carlo (DDMC) scheme has been successfully applied in state-of-the-art radiation hydrodynamics (RHD) simulations. Still, the established framework is not optimal for resonant line transfer. Inspired by the DDMC paradigm, we present a novel extension to resonant DDMC in which diffusion in space and frequency are treated on equal footing. We explore the robustness of our new method and demonstrate a level of performance that justifies incorporating the method into existing Ly\${\textbackslash}alpha\$ codes. We present computational speedups of \${\textbackslash}sim 10{\textasciicircum}2\$-\$10{\textasciicircum}6\$ relative to contemporary MCRT implementations with aggressive core-skipping. This is because the resonant DDMC runtime scales with the spatial and frequency resolution rather than the number of scatterings - the latter is typically \${\textbackslash}propto {\textbackslash}tau_0\$ for static media, or \${\textbackslash}propto (a {\textbackslash}tau_0){\textasciicircum}\{2/3\}\$ with core-skipping. We anticipate new frontiers in which on-the-fly Ly\${\textbackslash}alpha\$ radiative transfer calculations are feasible in 3D RHD. More generally, resonant DDMC is transferable to any computationally demanding problem amenable to a Fokker-Planck approximation of frequency redistribution.
@article{smith_discrete_2017,
	title = {Discrete diffusion {Lyman}-alpha radiative transfer},
	volume = {1709},
	url = {http://adsabs.harvard.edu/abs/2017arXiv170910187S},
	abstract = {Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Ly\${\textbackslash}alpha\$ radiative transfer in arbitrary geometries. The standard MCRT encounters a significant efficiency barrier in the high optical depth, diffusion regime. Multiple acceleration schemes have been developed to improve the efficiency of MCRT but the noise from photon packet discretization remains a challenge. The discrete diffusion Monte Carlo (DDMC) scheme has been successfully applied in state-of-the-art radiation
hydrodynamics (RHD) simulations. Still, the established framework is not optimal for resonant line transfer. Inspired by the DDMC paradigm, we present a novel extension to resonant DDMC in which diffusion in space and frequency are treated on equal footing. We explore the robustness of our new method and demonstrate a level of performance that justifies incorporating the method into existing Ly\${\textbackslash}alpha\$ codes. We present computational speedups of \${\textbackslash}sim 10{\textasciicircum}2\$-\$10{\textasciicircum}6\$ relative to contemporary MCRT implementations with aggressive core-skipping. This is because the resonant DDMC runtime scales with the spatial and frequency resolution rather than the number of scatterings - the latter is typically \${\textbackslash}propto {\textbackslash}tau\_0\$ for static media, or \${\textbackslash}propto (a {\textbackslash}tau\_0){\textasciicircum}\{2/3\}\$ with
core-skipping. We anticipate new frontiers in which on-the-fly
Ly\${\textbackslash}alpha\$ radiative transfer calculations are feasible in 3D RHD. More generally, resonant DDMC is transferable to any computationally
demanding problem amenable to a Fokker-Planck approximation of frequency redistribution.},
	journal = {ArXiv e-prints},
	author = {Smith, Aaron and Tsang, Benny T.-H. and Bromm, Volker and Milosavljevic, Milos},
	month = sep,
	year = {2017},
	keywords = {Astrophysics - Astrophysics of Galaxies, Astrophysics - Cosmology and Nongalactic Astrophysics, Physics - Computational Physics},
	pages = {arXiv:1709.10187},
}

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