A new Implicit Monte-Carlo scheme for photonics (without teleportation error and without tilts)

In this paper, we present a new implicit Monte-Carlo scheme for photonics. The new solver combines the benefits of both the IMC solver of Fleck & Cummings and the SMC solver of Ahrens & Larsen. It is implicit hence allows taking affordable time steps (as IMC) and has no teleportation error (as SMC). The paper also provides some original analysis of existing schemes (IMC, tilted IMC, SMC), especially with respect to the teleportation error in the equilibrium diffusion regime. In particular, we demonstrate that any small spatial inaccuracies during the sampling of source particles for IMC lead to a competing behaviour between the spatial and time discretisation parameters. The new scheme we suggest is implicit, conservative, has no teleportation error (and as a consequence does not need tilting), does not rely on source sampling for the emission of source particles, captures the equilibrium diffusion limit (provided a small enough time step), can be used with arbitrary equations of state and does not suffer the above competing behaviour. All those properties are either demonstrated or numerically highlighted in the paper. (C) 2020 Elsevier Inc. All rights reserved.