Crate spectroxide

spectroxide

An open-source solver for the cosmological thermalization problem: computing spectral distortions of the CMB from energy release in the early Universe.

Overview

The code evolves the photon occupation number n(x, z) (where x = hν/(kT_z) is the dimensionless frequency) through the coupled photon-electron Boltzmann equation in an expanding universe.

Physical processes included:

• Compton scattering (Kompaneets equation): frequency redistribution
• Double Compton emission: photon-number changing, γe → γγe
• Bremsstrahlung: photon-number changing, e+ion → e+ion+γ
• Hubble expansion: cosmological redshifting

Usage

use spectroxide::prelude::*;

// Create solver with default cosmology
let cosmo = Cosmology::default();
let mut solver = ThermalizationSolver::new(cosmo, GridConfig::fast());

// Set energy injection (e.g., delta-function burst at z=2×10⁵)
solver.set_injection(InjectionScenario::SingleBurst {
    z_h: 2e5,
    delta_rho_over_rho: 1e-5,
    sigma_z: 100.0,
}).unwrap();

// Run the solver, collecting 50 evenly log-spaced snapshots
let snapshots = solver.run(50);
let mu = snapshots.last().unwrap().mu;

Green’s Function Mode

For fast approximate calculations of small distortions:

use spectroxide::greens::*;

// Distortion from delta-function injection at z_h = 2×10⁵
let x = 3.0; // dimensionless frequency
let g = greens_function(x, 2e5);

Modules

bremsstrahlung

Bremsstrahlung (free-free) emission and absorption.

cli

CLI argument parsing with subcommands (zero dependencies).

constants

Physical and cosmological constants in SI units.

cosmology

Background cosmology: Hubble rate, cosmic time, number densities.

dark_photon

Helpers for dark photon (γ ↔ A’) conversion in the narrow-width approximation.

distortion

Distortion extraction and characterization.

double_compton

Double Compton (DC) scattering: γ + e → γ + γ + e

electron_temp

Electron temperature state (ρ_e = T_e/T_z).

energy_injection

Energy injection scenarios for the early Universe.

greens

Green’s function for the cosmological thermalization problem.

grid

Frequency grid for the photon Boltzmann equation.

kompaneets

Kompaneets equation: Compton scattering of photons off thermal electrons.

output

Structured output types and serialization for solver results.

prelude

Convenient imports for common usage.

recombination

Hydrogen and helium recombination history.

solver

Main PDE solver for the cosmological thermalization problem.

spectrum

Spectral shapes and distributions for CMB spectral distortions.

Constants

PHYSICS_HASH

Content hash of the physics-relevant Rust source files at compile time.