idm_drmd.h

#pragma once
#include "background.h"
#include "base_species.h"
#include "perturbations.h"
 
class IDM_DRMDSpecies : public BaseSpecies {
 public:
  IDM_DRMDSpecies(const background& pba, double omega0_idm_drmd)
      : BaseSpecies("IDM_DRMD", EnergyType::Matter), pba_(pba), Omega0_idm_drmd_(omega0_idm_drmd) {}
 
  double GetOmega0() const override {
    return Omega0_idm_drmd_;
  }
 
  void RegisterBackgroundIndices(int& index_bg) override {
    index_bg_rho_ = index_bg++;
  }
 
  void ComputeBackground(double a, const double* /*pvecback_B*/, double* pvecback) override {
    pvecback[index_bg_rho_] = Omega0_idm_drmd_ * pba_.H0 * pba_.H0 / (a * a * a);
  }
 
  double Rho(const double* pvecback) const override {
    return pvecback[index_bg_rho_];
  }
  double P(const double* /*pvecback*/) const override {
    return 0.;
  }
 
  // ── PerturbLayout ──────────────────────────────────────────────────────────
 
  struct PerturbLayout : BaseSpecies::PerturbLayout {
    int idx_delta = -1;  
    int idx_theta = -1;  
  };
 
  std::unique_ptr<BaseSpecies::PerturbLayout> CreatePerturbLayout() const override {
    return std::make_unique<PerturbLayout>();
  }
 
  // ── Perturbation index registration ────────────────────────────────────────
 
  void RegisterPerturbationIndices(BaseSpecies::PerturbLayout& layout,
                                   perturb_vector* pv,
                                   const precision* ppr,
                                   int& index_pt,
                                   const perturb_workspace* ppw,
                                   int gauge) override;
 
  // ── PerturbDerivs ──────────────────────────────────────────────────────────
 
  void PerturbDerivs(const BaseSpecies::PerturbLayout& layout,
                     double tau,
                     const double* y,
                     double* dy,
                     const perturb_parameters_and_workspace& ppaw) const override;
 
  // ── Stress-energy observables ───────────────────────────────────────────────
 
  StressEnergyContribution StressEnergy(const BaseSpecies::PerturbLayout& layout,
                                        const perturb_vector* pv,
                                        const double* y,
                                        const double* pvecback,
                                        const perturb_workspace* ppw) const override;
 
  void PerturbSynchronousToNewtonian(const BaseSpecies::PerturbLayout& layout,
                                     double* y,
                                     const PerturbIcContext& ctx) override;
 
  // ── Switch-copy hook ────────────────────────────────────────────────────────
 
  void CopyPerturbationsAcrossSwitch(const BaseSpecies::PerturbLayout& old_layout,
                                     const BaseSpecies::PerturbLayout& new_layout,
                                     const double* old_y,
                                     double* new_y,
                                     const PerturbSwitchContext& ctx) const override;
 
 private:
  const background& pba_;
  double Omega0_idm_drmd_;
};