Comparison between BSSN_MoL (ADM_BSSN) and McLachlan (ML_BSSN) parameters

2009-11-14: Written by Erik Schnetter
2010-03-29: Cross-checked by Peter Diener, fixed a few issues with the gauge
            parameters and (hopefully) clarified things a bit.

Activation:

ActiveThorns = "BSSN_MoL"
        ActiveThorns = "ML_BSSN ML_BSSN_Helper"

Formulation:

ADMBase::evolution_method = "ADM_BSSN"
        ADMBase::evolution_method = "ML_BSSN"

ADM_BSSN::RfromH = yes
        [always for ML_BSSN]

ADM_BSSN::bound = "radiative"
        ML_BSSN::my_initial_boundary_condition = "extrapolate-gammas"
        ML_BSSN::my_rhs_boundary_condition     = "NewRad"
        # These are necessary
        ML_BSSN::ML_log_confac_bound = "none"
        ML_BSSN::ML_metric_bound     = "none"
        ML_BSSN::ML_Gamma_bound      = "none"
        ML_BSSN::ML_trace_curv_bound = "none"
        ML_BSSN::ML_curv_bound       = "none"
        ML_BSSN::ML_lapse_bound      = "none"
        ML_BSSN::ML_dtlapse_bound    = "none"
        ML_BSSN::ML_shift_bound      = "none"
        ML_BSSN::ML_dtshift_bound    = "none"

Boundary::radpower
        Boundary::radpower



Lapse:

ADMBase::lapse_evolution_method = "1+log"
        ADMBase::lapse_evolution_method   = "ML_BSSN"
        ADMBase::dtlapse_evolution_method = "ML_BSSN"
        ML_BSSN::harmonicN = 1   # 1+log

ADM_BSSN::lapsesource = "straight"
        ML_BSSN::LapseAdvectionCoeff = 1
        [This can only be done with the shift advection terms on the lapse]
ADM_BSSN::lapsesource = "modified"
        ML_BSSN::AlphaDriver = 1
	ML_BSSN::LapseAdvectionCoeff = 0
        [This can only be done with the shift advection terms turned off]

ADM_BSSN::harmonic_f
        ML_BSSN::harmonicF

ADM_BSSN::force_lapse_positive = yes
        [always for ML_BSSN, but MinimumLapse can be negative]
ADM_BSSN::force_lapse_minimum
        ML_BSSN::MinimumLapse

ADM_BSSN::lapse_advection_coeff
        ML_BSSN::LapseAdvectionCoeff
        [should be 0 or 1. Note that in McLachlan this also selects
        between using the 1st time derivative lapse or not. Maybe this
        should be changed.]



Shift:

ADMBase::shift_evolution_method = "gamma0"
        ADMBase::shift_evolution_method   = "ML_BSSN"
        ADMBase::dtshift_evolution_method = "ML_BSSN"
        ML_BSSN::ShiftGammaCoeff = 0
ADMBase::shift_evolution_method = "gamma1"
        [Not implemnted in ML_BSSN]
ADMBase::shift_evolution_method = "gamma2"
        [Not implemnted in ML_BSSN]

ADM_BSSN::ShiftGammaCoeff
        ML_BSSN::ShiftGammaCoeff
        [Normally chosen to be 0.75 for moving puncture gauges]

ADM_BSSN::ShiftAlpPower = 0
        [always for ML_BSSN]
        [There is a parameter ML_BSSN::ShiftAlphaPower, but it is unused]

ADM_BSSN::GammaDriver
        [has no effect in ADM_BSSN and is not implemented in ML_BSSN]

ADM_BSSN::BetaDriver
        ML_BSSN::BetaDriver

ADM_BSSN::gamma_driver_advection_coeff
        ML_BSSN::ShiftAdvectionCoeff
        [should be 0 or 1. For moving puncture gauges 1 should be chosen]

ADM_BSSN::ApplyShiftBoundary = no
        [not possible with ML_BSSN; shift boundary is always applied]



Discretisation:

ADM_BSSN::timelevels
        ML_BSSN::timelevels

ADM_BSSN::advection = "upwind4"
        [always for ML_BSSN when 4th order is used]