Struct SphericalHarmonicsPoisson 

pub struct SphericalHarmonicsPoisson {
    pub l_max: usize,
    pub n_radial: usize,
    pub r_max: f64,
    pub shape: [usize; 3],
    pub dx: [f64; 3],
}

Spherical-harmonics expansion Poisson solver.

Best suited for nearly-spherical density distributions (isolated halos, stellar systems). The expansion is truncated at degree l_max, and the radial direction is discretized into n_radial bins from 0 to r_max.

Fields

l_max: usize

n_radial: usize

r_max: f64

shape: [usize; 3]

dx: [f64; 3]

Implementations

impl SphericalHarmonicsPoisson

pub fn new( l_max: usize, n_radial: usize, shape: [usize; 3], dx: [f64; 3], ) -> Self

Create a new spherical-harmonics Poisson solver.

l_max: maximum spherical harmonic degree (0 = monopole only). n_radial: number of radial bins for the 1D Poisson solve. shape: grid dimensions [nx, ny, nz]. dx: cell spacings [dx, dy, dz].

Trait Implementations

impl PoissonSolver for SphericalHarmonicsPoisson

fn solve(&self, density: &DensityField, g: f64) -> PotentialField

Solve nabla^2 Phi = 4 pi G rho via spherical harmonic decomposition.

Steps:

1. Decompose density into radial profiles rho_lm(r) for each (l,m).
2. Solve the radial Poisson equation for each mode.
3. Reconstruct the Cartesian potential by summing Phi_lm(r) Y_lm(theta,phi).

fn compute_acceleration(&self, potential: &PotentialField) -> AccelerationField

Compute gravitational acceleration g = -nabla Phi via centered finite differences on the Cartesian grid.