Struct HybridRepr 

pub struct HybridRepr {
    pub sheet: SheetTracker,
    pub grid: UniformGrid6D,
    pub domain: Domain,
    pub stream_threshold: u32,
    pub mask: Vec<bool>,
}

Hybrid representation combining SheetTracker and UniformGrid6D.

Single-stream regions (stream_count ≤ threshold) are tracked by the Lagrangian sheet (exact characteristics, zero diffusion). Multi-stream regions are handled by the Eulerian 6D grid (captures velocity dispersion).

The mask vector marks each spatial cell: true = grid mode, false = sheet mode.

Fields

sheet: SheetTracker

grid: UniformGrid6D

domain: Domain

stream_threshold: u32

mask: Vec<bool>

Per spatial cell: true = grid mode (multi-stream), false = sheet mode.

Implementations

impl HybridRepr

pub fn new(domain: Domain) -> Self

pub fn update_interface(&mut self)

Transfer particles from SheetTracker to grid where stream_count > stream_threshold.

For each spatial cell where the stream count exceeds the threshold and is not yet in grid mode: deposit the sheet particles into the 6D grid via CIC and mark the cell as grid mode.

Trait Implementations

impl PhaseSpaceRepr for HybridRepr

fn compute_density(&self) -> DensityField

Integrate f over all velocities: ρ(x) = ∫f dv³. This is the coupling moment to the Poisson equation.

fn advect_x(&mut self, displacement: &DisplacementField, dt: f64)

Drift sub-step: advect f in spatial coordinates by displacement Δx = v·dt. Pure translation in x at constant v.

fn advect_v(&mut self, acceleration: &AccelerationField, dt: f64)

Kick sub-step: advect f in velocity coordinates by Δv = g·dt. Pure translation in v at constant x.

fn moment(&self, position: &[f64; 3], order: usize) -> Tensor

Compute velocity moment of order n at given spatial position. Order 0 = density, 1 = mean velocity, 2 = dispersion tensor.

fn total_mass(&self) -> f64

Total mass M = ∫f dx³dv³. Should be conserved to machine precision.

fn casimir_c2(&self) -> f64

Casimir invariant C₂ = ∫f² dx³dv³. Increase over time indicates numerical diffusion.

fn entropy(&self) -> f64

Boltzmann entropy S = −∫f ln f dx³dv³. Should be exactly conserved; growth = numerical error.

fn stream_count(&self) -> StreamCountField

Number of distinct velocity streams at each spatial point. Detects caustic surfaces (sheet folds).

fn velocity_distribution(&self, position: &[f64; 3]) -> Vec<f64>

Extract the local velocity distribution f(v|x) at a given spatial position. Used for dark matter detection predictions.

fn total_kinetic_energy(&self) -> f64

Total kinetic energy T = ½∫fv² dx³dv³.

fn as_any(&self) -> &dyn Any

Downcast to concrete type for implementation-specific queries (e.g. HT rank data).

fn to_snapshot(&self, time: f64) -> PhaseSpaceSnapshot

Extract a full 6D snapshot of the current state.

fn load_snapshot(&mut self, snap: PhaseSpaceSnapshot)

Replace the current state with data from a dense 6D snapshot.