N-body Code with Adaptive Mesh Refinement

Abstract

We have developed a simulation code with the techniques which enhance both spatial and time resolution of the PM method for which the spatial resolution is restricted by the spacing of structured mesh. The adaptive mesh refinement (AMR) technique subdivides the cells which satisfy the refinement criterion recursively. The hierarchical meshes are maintained by the special data structure and are modified in accordance with the change of particle distribution. In general, as the resolution of the simulation increases, its time step must be shortened and more computational time is required to complete the simulation. Since the AMR enhances the spatial resolution locally, we reduce the time step locally also, instead of shortening it globally. For this purpose we used a technique of hierarchical time steps (HTS) which changes the time step, from particle to particle, depending on the size of the cell in which particles reside. Some test calculations show that our implementation of AMR and HTS is successful. We have performed cosmological simulation runs based on our code and found that many of halo objects have density profiles which are well fitted to the universal profile proposed by Navarro, Frenk, & White (1996) over the entire range of their radius.

Electromagnetic full particle code with adaptive mesh refinement technique: Application to the current sheet evolution

“…The solutions are interpolated onto the buffer cell corners on the next level cells as the boundary conditions as shown in Fig. 3 [40]. The interpolations are simply performed in the linear form,…”

“…An introduction of the AMR technique to a particle code has been examined for the application to the N-body simulations describing cosmological matter such as the formation and structure of galaxies [12,18,20,21,32,35,39,40]. In the Nbody codes, the mass density is assigned to the neighboring grids using the cloud-in-cell (CIC) algorithm, which is equivalent to the PIC algorithm for orthogonal coordinates [6].…”

“…The ART code subdivides all cells that satisfy a refinement criterion regardless of the shape of the refined regions, so that it enables us to achieve an efficient refinement to cover a complicate structure. Although their code is adaptive only in space, recently developed codes [20,35,40] are adaptive not only in space but also in time. Plasma simulations using an electrostatic PIC code with the AMR have been recently examined in order to describe the ion beam transport in a heavy ion fusion [37].…”

Full particle simulation of the plasma sheet using adaptive mesh refinement technique

“…We add the pointer, inp, directed to a representative superparticle from each oct so as to identify the oct in which the superparticle resides. cells that satisfy a refinement criterion (Yahagi and Yoshii, 2001). Then electromagnetic field is calculated on the cells with this level.…”