cosmotool/src/growthFactor.cpp

112 lines
2.6 KiB
C++
Raw Normal View History

#include <cmath>
#include <gsl/gsl_integration.h>
#include "interpolate.hpp"
#include "growthFactor.hpp"
using namespace CosmoTool;
#define AMIN 1e-5
#define AMAX 1.0
#define NUM_WORK 5000
#define TOLERANCE 1e-6
typedef struct {
double OmegaLambda;
double OmegaMatter;
double Hubble;
} Cosmology;
static double computeOmegaMatter(Cosmology *cosmo, double a)
{
return cosmo->OmegaMatter / (cosmo->OmegaMatter + a*a*a * cosmo->OmegaLambda);
}
static double computeHdotH(Cosmology *cosmo, double a)
{
return -1.5 * cosmo->OmegaMatter / (a * (cosmo->OmegaMatter + a*a*a*cosmo->OmegaLambda));
}
static double computeE(double OmegaMatter, double OmegaLambda, double a)
{
double H2;
double OmegaK = (1 - OmegaMatter - OmegaLambda);
H2 = OmegaMatter/(a*a*a) + OmegaLambda + OmegaK/(a*a);
return sqrt(H2);
}
static double computeEprime(Cosmology *cosmo, double a)
{
double H2;
double OmegaK = (1 - cosmo->OmegaMatter - cosmo->OmegaLambda);
H2 = -3*cosmo->OmegaMatter/(a*a*a*a) - 2*OmegaK/(a*a*a);
return 0.5*H2/computeE(cosmo->OmegaMatter, cosmo->OmegaLambda, a);
}
static inline double cube(double x)
{
return x*x*x;
}
static double integrandGrowthFactor(double a, void *params)
{
Cosmology *cosmo = (Cosmology *)params;
return 1/cube(computeE(cosmo->OmegaMatter, cosmo->OmegaLambda, a)*a);
}
Interpolate CosmoTool::buildLinearGrowth(double OmegaLambda, double OmegaMatter, double Hubble, int numPoints)
{
Cosmology cosmology;
gsl_integration_workspace *work = gsl_integration_workspace_alloc(NUM_WORK);
gsl_function f;
double *a_input, *D_output;
cosmology.OmegaLambda = OmegaLambda;
cosmology.OmegaMatter = OmegaMatter;
cosmology.Hubble = Hubble;
a_input = new double[numPoints];
D_output = new double[numPoints];
f.params = &cosmology;
f.function = integrandGrowthFactor;
2010-12-02 00:09:14 +01:00
a_input[0] = 0;
D_output[0] = 0;
for (int i = 1; i < numPoints; i++)
{
double a_dest = 0 + 1.0*i/(numPoints-1);
double result, abserr;
double E = computeE(cosmology.OmegaMatter, cosmology.OmegaLambda, a_dest);
double Eprime = computeEprime(&cosmology, a_dest);
gsl_integration_qag(&f, 0, a_dest, 0, TOLERANCE, NUM_WORK,
GSL_INTEG_GAUSS61, work, &result, &abserr);
result *= 2.5 * computeE(cosmology.OmegaMatter, cosmology.OmegaLambda, a_dest) * OmegaMatter;
D_output[i] = result;
a_input[i] = a_dest;
}
gsl_integration_workspace_free(work);
for (int i = 0; i < numPoints; i++)
{
D_output[i] /= D_output[numPoints-1];
}
Interpolate p(a_input, D_output, numPoints, true, false, true);
delete[] a_input;
delete[] D_output;
return p;
}