I'm attempting to reproduce figure 1 of Scott et al. 2016 (https://arxiv.org/abs/1603.03550), but my results don't match the paper at all at low multipoles. Please see my attempt at reproducing figure 1 for [math]. At low multipoles, my TT curve has a dip at [math] where the Scott et al. curve does not. This is only the most glaring difference; none of the curves match at low multipoles.

To try to debug the problem, I plotted [math] as a function of [math].

Because the Fisher matrix (especially in this case) depends essentially on the square of the derivative, I also plotted the absolute value, and the dip at [math] appears.

I spoke with Dr. Scott about this, and he points out that this dip is unphysical. He suggested I check the accuracy at low multipoles, because he had similar difficulties when he was developing the paper, but couldn't recall exactly what he had to do to correct it.

Here is my CAMBpars instance that I'm using to get the [math].

Code: Select all

```
Using CAMB version 1.0.8
class: <CAMBparams>
WantCls = True
WantTransfer = False
WantScalars = True
WantTensors = False
WantVectors = False
WantDerivedParameters = True
Want_cl_2D_array = True
Want_CMB = True
Want_CMB_lensing = True
DoLensing = True
NonLinear = NonLinear_lens
Transfer: <TransferParams>
high_precision = False
accurate_massive_neutrinos = False
kmax = 0.9
k_per_logint = 0
PK_num_redshifts = 1
PK_redshifts = [0.0]
want_zstar = False
want_zdrag = False
min_l = 2
max_l = 3149
max_l_tensor = 600
max_eta_k = 18000.0
max_eta_k_tensor = 1200.0
ombh2 = 0.022277
omch2 = 0.11843
omk = 0.0
omnuh2 = 0.000645138398938
H0 = 67.8708311184
TCMB = 2.7255
YHe = 0.245361301871
num_nu_massless = 2.03066666667
num_nu_massive = 1
nu_mass_eigenstates = 1
share_delta_neff = False
nu_mass_degeneracies = [1.0153333333333332]
nu_mass_fractions = [1.0]
nu_mass_numbers = [1]
InitPower: <InitialPowerLaw>
tensor_parameterization = tensor_param_rpivot
ns = 0.9683
nrun = 0.0
nrunrun = 0.0
nt = -0.0
ntrun = -0.0
r = 0.0
pivot_scalar = 0.05
pivot_tensor = 0.05
As = 2.14044747364e-09
At = 1.0
Recomb: <Recfast>
min_a_evolve_Tm = 0.00110987795051
RECFAST_fudge = 1.125
RECFAST_fudge_He = 0.86
RECFAST_Heswitch = 6
RECFAST_Hswitch = True
AGauss1 = -0.14
AGauss2 = 0.079
zGauss1 = 7.28
zGauss2 = 6.73
wGauss1 = 0.18
wGauss2 = 0.33
Reion: <TanhReionization>
Reionization = True
use_optical_depth = True
redshift = 10.0
optical_depth = 0.0666
delta_redshift = 0.5
fraction = -1.0
include_helium_fullreion = True
helium_redshift = 3.5
helium_delta_redshift = 0.4
helium_redshiftstart = 5.5
tau_solve_accuracy_boost = 1.0
timestep_boost = 1.0
max_redshift = 50.0
DarkEnergy: <DarkEnergyFluid>
w = -1.0
wa = 0.0
cs2 = 1.0
use_tabulated_w = False
NonLinearModel: <Halofit>
Min_kh_nonlinear = 0.005
halofit_version = mead
HMCode_A_baryon = 3.13
HMCode_eta_baryon = 0.603
Accuracy: <AccuracyParams>
AccuracyBoost = 1.0
lSampleBoost = 1.0
lAccuracyBoost = 1.0
AccuratePolarization = True
AccurateBB = False
AccurateReionization = True
TimeStepBoost = 1.0
BackgroundTimeStepBoost = 1.0
IntTolBoost = 1.0
SourcekAccuracyBoost = 1.0
IntkAccuracyBoost = 1.0
TransferkBoost = 1.0
NonFlatIntAccuracyBoost = 1.0
BessIntBoost = 1.0
LensingBoost = 1.0
NonlinSourceBoost = 1.0
BesselBoost = 1.0
LimberBoost = 1.0
SourceLimberBoost = 1.0
KmaxBoost = 1.0
neutrino_q_boost = 1.0
SourceTerms: <SourceTermParams>
limber_windows = True
limber_phi_lmin = 100
counts_density = True
counts_redshift = True
counts_lensing = False
counts_velocity = True
counts_radial = False
counts_timedelay = True
counts_ISW = True
counts_potential = True
counts_evolve = False
line_phot_dipole = False
line_phot_quadrupole = False
line_basic = True
line_distortions = True
line_extra = False
line_reionization = False
use_21cm_mK = True
z_outputs = []
scalar_initial_condition = initial_adiabatic
InitialConditionVector = []
OutputNormalization = 1
Alens = 1.0
MassiveNuMethod = Nu_best
DoLateRadTruncation = True
Evolve_baryon_cs = False
Evolve_delta_xe = False
Evolve_delta_Ts = False
Do21cm = False
transfer_21cm_cl = False
Log_lvalues = False
use_cl_spline_template = True
SourceWindows = []
CustomSources: <CustomSources>
num_custom_sources = 0
c_source_func = None
custom_source_ell_scales = []
```