%0 Generic %1 smith2017discrete %A Smith, Aaron %A Tsang, Benny T. H. %A Bromm, Volker %A Milosavljevic, Milos %D 2017 %K Lya algorithm radiative transfer %T Discrete diffusion Lyman-alpha radiative transfer %U http://arxiv.org/abs/1709.10187 %X Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Ly$\alpha$ 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$\alpha$ codes. We present computational speedups of $\sim 10^2$-$10^6$ 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 $\tau_0$ for static media, or $(a \tau_0)^2/3$ with core-skipping. We anticipate new frontiers in which on-the-fly Ly$\alpha$ 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.

@misc{smith2017discrete, abstract = {Due to its accuracy and generality, Monte Carlo radiative transfer (MCRT) has emerged as the prevalent method for Ly$\alpha$ 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$\alpha$ codes. We present computational speedups of $\sim 10^2$-$10^6$ 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 $\propto \tau_0$ for static media, or $\propto (a \tau_0)^{2/3}$ with core-skipping. We anticipate new frontiers in which on-the-fly Ly$\alpha$ 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.}, added-at = {2017-10-02T10:39:51.000+0200}, author = {Smith, Aaron and Tsang, Benny T. H. and Bromm, Volker and Milosavljevic, Milos}, biburl = {https://www.bibsonomy.org/bibtex/2dc7080895bc9b07b05c1cb3f1c464f29/miki}, description = {[1709.10187] Discrete diffusion Lyman-alpha radiative transfer}, interhash = {07d680302b6c7afd0b3917036379aa55}, intrahash = {dc7080895bc9b07b05c1cb3f1c464f29}, keywords = {Lya algorithm radiative transfer}, note = {cite arxiv:1709.10187Comment: 13 pages, 12 figures, MNRAS, submitted}, timestamp = {2017-10-02T10:39:51.000+0200}, title = {Discrete diffusion Lyman-alpha radiative transfer}, url = {http://arxiv.org/abs/1709.10187}, year = 2017 }