I'm having some computational problems with the following code:
import numpy as np
from numpy import arange
from scipy.integrate import odeint
import matplotlib.pyplot as plt
from scipy.integrate import quad
import matplotlib as mpl
mpl.rcParams['agg.path.chunksize'] = 10000
# parameters
Ms = 100 #GeV Singlet Mass
Me = 0.511e-3 #Gev Electron Mass
Mp = 1.22e19 #GeV Planck Mass
gs = 106.75 # Entropy dof
H0 = 2.133*(0.7)*1e-42 # GeV Hubble parameter (unused)
gx = 2 # WIMP's dof
g = 100 # total dof
sigmav=[1e-25,1e-11,1e-12] # cross section's order of magnitude
xi=1e-2
xe=1e2
npts=int(1e5)
x = np.linspace(xi, xe, npts)
def fMB(p,x,m):
return np.exp(-x*np.sqrt(1+p*p/(m*m)))*p*p
def neq(x,m):
return (gx/(2*np.pi*np.pi))*quad(fMB, 0, np.inf, args=(x,m))[0]
def neq_nr(x,m):
return 2*(m**2/(2*np.pi*x))**(3/2)*np.exp(-x)
def stot(x):
return (2*np.pi*np.pi/45)*gs*Ms*Ms*Ms/(x*x*x)
def Yeq(x,m):
return neq(x,m)/stot(x)
Yeq2=np.vectorize(Yeq)
def Yeq_nr(x):
return 0.145*(gx/gs)*(x)**(3/2)*np.exp(-x)
def Yeq_r(x):
return 0.278*(3*gx/4)/gs
def Ytot(x):
if np.any(x<=1):
return Yeq_r(x)
else:
return Yeq_nr(x)
def eqd(yl,x,Ms,σv):
'''
Ms [GeV] : Singlet Mass
σv: [1/GeV^2] : ⟨σv⟩
'''
H = 1.67*g**(1/2)*Ms**2/Mp
dyl = -neq(x,Ms)*σv*(yl**2-Yeq(x,Ms)**2)/(x**(-2)*H*x*Yeq(x,Ms)) #occorre ancora dividere per Yeq_nr(x) oppure Yeq(x)
return dyl
y0=1e-15
yl0 = odeint( eqd, y0, x,args=(Ms,sigmav[0]), full_output=True)
yl1 = odeint( eqd, y0, x,args=(Ms,sigmav[1]), full_output=True)
yl2 = odeint( eqd, y0, x,args=(Ms,sigmav[2]), full_output=True)
fig = plt.figure(figsize=(11,8))
plt.loglog(x,yl0[0], label = r'$\langle σ v\rangle = %s {\rm GeV}^{-2}$'%(sigmav[0]))
plt.loglog(x,yl1[0], label = r'$\langle σ v\rangle = %s {\rm GeV}^{-2}$'%(sigmav[1]))
plt.loglog(x,yl2[0], label = r'$\langle σ v\rangle = %s {\rm GeV}^{-2}$'%(sigmav[2]))
plt.loglog(x,Yeq_nr(x), '--', label = '$Y_{EQ}^{nr}$')
plt.loglog(x,Yeq2(x,Ms), '--', label = '$Y_{EQ}$')
plt.ylim(ymax=0.1,ymin=y0)
plt.xlim(xmax=xe,xmin=xi)
plt.xlabel('$x = m_χ/T$', size= 15)
plt.ylabel('$Y$', size= 15)
plt.title('$m_χ = %s$ GeV'%(Ms), size= 15)
plt.legend(loc='best',fontsize=12)
plt.grid(True)
plt.savefig('abundance.jpg',bbox_inches='tight', dpi=150)
In particular, as soon as I use little values of sigmav (ranging from 10^-12 to 10^-25) the solution is well displayed, but making use of bigger values (starting from 10^-11) I obtain problems and I guess is a order of magnitudes problem, but I don't know how to handle it!
Thanks to everyone!
Edit 1: I'm uploading a plot making use of three different values of sigmav and as you may see the bigger one (1e-10) is showing (I guess) precision problems plot_1