mirror of
https://github.com/glatterf42/music-panphasia.git
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224 lines
7.1 KiB
C++
224 lines
7.1 KiB
C++
/*
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cosmology.hh - This file is part of MUSIC -
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a code to generate multi-scale initial conditions
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for cosmological simulations
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Copyright (C) 2010 Oliver Hahn
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*/
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#ifndef _COSMOLOGY_HH
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#define _COSMOLOGY_HH
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#include "transfer_function.hh"
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#include "mesh.hh"
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#include "general.hh"
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/*!
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* @class CosmoCalc
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* @brief provides functions to compute cosmological quantities
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*
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* This class provides member functions to compute cosmological quantities
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* related to the Friedmann equations and linear perturbation theory
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*/
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class CosmoCalc
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{
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public:
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//! data structure to store cosmological parameters
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Cosmology m_Cosmology;
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//! pointer to an instance of a transfer function plugin
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transfer_function_plugin *m_pTransferFunction;
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//! constructor for a cosmology calculator object
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/*!
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* @param acosmo a cosmological parameters structure
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* @param pTransferFunction pointer to an instance of a transfer function object
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*/
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CosmoCalc( const Cosmology acosmo, transfer_function_plugin *pTransferFunction )
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{
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m_Cosmology = acosmo;
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m_pTransferFunction = pTransferFunction;
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}
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//! returns the amplitude of amplitude of the power spectrum
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/*!
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* @param k the wave number in h/Mpc
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* @param a the expansion factor of the universe
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* @returns power spectrum amplitude for wave number k at time a
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*/
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inline real_t Power( real_t k, real_t a ){
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real_t m_Dplus = CalcGrowthFactor( a );
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real_t m_DplusOne = CalcGrowthFactor( 1.0 );
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real_t m_pNorm = ComputePNorm( 1e4 );
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m_Dplus /= m_DplusOne;
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m_DplusOne = 1.0;
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real_t scale = m_Dplus/m_DplusOne;
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return m_pNorm*scale*scale*TransferSq(k)*pow((double)k,(double)m_Cosmology.nspect);
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}
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inline static double H_of_a( double a, void *Params )
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{
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Cosmology *cosm = (Cosmology*)Params;
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double a2 = a*a;
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double Ha = sqrt(cosm->Omega_m/(a2*a) + cosm->Omega_k/a2
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+ cosm->Omega_DE * pow(a,-3.*(1.+cosm->w_0+cosm->w_a)) * exp(-3.*(1.0-a)*cosm->w_a) );
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return Ha;
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}
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inline static double Hprime_of_a( double a, void *Params )
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{
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Cosmology *cosm = (Cosmology*)Params;
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double a2 = a*a;
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double H = H_of_a( a, Params );
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double Hprime = 1/(a*H) * ( -1.5 * cosm->Omega_m / (a2*a) - cosm->Omega_k / a2
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- 1.5 * cosm->Omega_DE * pow( a, -3.*(1.+cosm->w_0+cosm->w_a) ) * exp( -3.*(1.0-a)*cosm->w_a )
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* ( 1. + cosm->w_0 + (1.-a) * cosm->w_a ) );
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return Hprime;
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}
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//! Integrand used by function CalcGrowthFactor to determine the linear growth factor D+
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inline static double GrowthIntegrand( double a, void *Params )
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{
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double Ha = a * H_of_a( a, Params );
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return 2.5/( Ha * Ha * Ha );
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}
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//! Computes the linear theory growth factor D+
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/*! Function integrates over member function GrowthIntegrand and computes
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* /a
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* D+(a) = 5/2 H(a) * | [a'^3 * H(a')^3]^(-1) da'
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* /0
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*/
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real_t CalcGrowthFactor( real_t a )
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{
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real_t integral = integrate( &GrowthIntegrand, 0.0, a, (void*)&m_Cosmology );
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return H_of_a( a, (void*)&m_Cosmology ) * integral;
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}
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//! Compute the factor relating particle displacement and velocity
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/*! Function computes
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*
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* vfac = a^2 * H(a) * dlogD+ / d log a = a^2 * H'(a) + 5/2 * [ a * D+(a) * H(a) ]^(-1)
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*
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*/
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real_t CalcVFact( real_t a )
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{
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real_t Dp = CalcGrowthFactor( a );
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real_t H = H_of_a( a, (void*)&m_Cosmology );
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real_t Hp = Hprime_of_a( a, (void*)&m_Cosmology );
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real_t a2 = a*a;
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return ( a2 * Hp + 2.5 / ( a * Dp * H ) ) * 100.0;
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}
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//! Integrand for the sigma_8 normalization of the power spectrum
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/*! Returns the value of the primordial power spectrum multiplied with
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the transfer function and the window function of 8 Mpc/h at wave number k */
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static double dSigma8( double k, void *Params )
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{
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if( k<=0.0 )
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return 0.0f;
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transfer_function *ptf = (transfer_function *)Params;
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double x = k*8.0;
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double w = 3.0*(sin(x)-x*cos(x))/(x*x*x);
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static double nspect = (double)ptf->cosmo_.nspect;
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double tf = ptf->compute(k, total);
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//... no growth factor since we compute at z=0 and normalize so that D+(z=0)=1
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return k*k * w*w * pow((double)k,(double)nspect) * tf*tf;
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}
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//! Integrand for the sigma_8 normalization of the power spectrum
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/*! Returns the value of the primordial power spectrum multiplied with
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the transfer function and the window function of 8 Mpc/h at wave number k */
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static double dSigma8_0( double k, void *Params )
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{
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if( k<=0.0 )
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return 0.0f;
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transfer_function *ptf = (transfer_function *)Params;
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double x = k*8.0;
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double w = 3.0*(sin(x)-x*cos(x))/(x*x*x);
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static double nspect = (double)ptf->cosmo_.nspect;
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double tf = ptf->compute(k, total0);
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//... no growth factor since we compute at z=0 and normalize so that D+(z=0)=1
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return k*k * w*w * pow((double)k,(double)nspect) * tf*tf;
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}
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//! Computes the square of the transfer function
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/*! Function evaluates the supplied transfer function m_pTransferFunction
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* and returns the square of its value at wave number k
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* @param k wave number at which to evaluate the transfer function
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*/
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inline real_t TransferSq( real_t k ){
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//.. parameter supplied transfer function
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real_t tf1 = m_pTransferFunction->compute(k, total);
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return tf1*tf1;
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}
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//! Computes the normalization for the power spectrum
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/*!
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* integrates the power spectrum to fix the normalization to that given
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* by the sigma_8 parameter
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*/
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real_t ComputePNorm( real_t kmax )
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{
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real_t sigma0, kmin;
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kmax = m_pTransferFunction->get_kmax();//m_Cosmology.H0/8.0;
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kmin = m_pTransferFunction->get_kmin();//0.0;
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if( !m_pTransferFunction->tf_has_total0() )
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sigma0 = 4.0 * M_PI * integrate( &dSigma8, (double)kmin, (double)kmax, (void*)m_pTransferFunction );
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else
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sigma0 = 4.0 * M_PI * integrate( &dSigma8_0, (double)kmin, (double)kmax, (void*)m_pTransferFunction );
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return m_Cosmology.sigma8*m_Cosmology.sigma8/sigma0;
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}
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};
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//! compute the jeans sound speed
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/*! given a density in g/cm^-3 and a mass in g it gives back the sound
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* speed in cm/s for which the input mass is equal to the jeans mass
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* @param rho density
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* @param mass mass scale
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* @returns jeans sound speed
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*/
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inline double jeans_sound_speed( double rho, double mass )
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{
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const double G = 6.67e-8;
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return pow( 6.0*mass/M_PI*sqrt(rho)*pow(G,1.5), 1.0/3.0 );
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}
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//! computes the density from the potential using the Laplacian
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void compute_Lu_density( const grid_hierarchy& u, grid_hierarchy& fnew, unsigned order=4 );
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//! computes the 2nd order density perturbations using also off-diagonal terms in the potential Hessian
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void compute_LLA_density( const grid_hierarchy& u, grid_hierarchy& fnew, unsigned order=4 );
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//! computes the source term for the 2nd order perturbations in the displacements
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void compute_2LPT_source( const grid_hierarchy& u, grid_hierarchy& fnew, unsigned order=4 );
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void compute_2LPT_source_FFT( config_file& cf_, const grid_hierarchy& u, grid_hierarchy& fnew );
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#endif // _COSMOLOGY_HH
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