def _get_coorbital_frame_spins_at_idx(self, chiA, chiB, omega, lNhat, phi, \
idx):
""" Computes PN spins and dynamics at a given idx.
Inputs:
chiA: Dimless spin evolution of BhA in inertial frame.
chiB: Dimless spin evolution of BhB in inertial frame.
omega: Orbital frequency evolution in dimless units.
lNhat: Orbital angular momentum direction evolution.
phi: Orbital phase evolution.
idx: Index for output.
Outputs (all are time series):
chiA_at_idx_coorb: Spin of BhA at idx, in coorbital frame.
chiB_at_idx_coorb: Spin of BhB at idx, in coorbital frame.
quat_copr_at_idx: Coprecessing frame quaternion at idx.
phi_at_idx: Orbital phase in the coprecessing frame at idx.
omega_at_idx Dimensionless orbital frequency at idx.
The inertial frame is assumed to be aligned to the coorbital frame at
the first index.
"""
# Compute omega, inertial spins, angular momentum direction and orbital
# phase at idx
omega_at_idx = omega[idx]
chiA_at_idx = chiA[idx]
chiB_at_idx = chiB[idx]
lNhat_at_idx = lNhat[idx]
phi_at_idx = phi[idx]
# Align the z-direction along orbital angular momentum direction
# at idx. This moves us in to the coprecessing frame.
quat_copr_at_idx = utils.alignVec_quat(lNhat_at_idx)
chiA_at_idx_copr = utils.transformTimeDependentVector(
np.array([quat_copr_at_idx]).T,
np.array([chiA_at_idx]).T,
inverse=1).T[0]
chiB_at_idx_copr = utils.transformTimeDependentVector(
np.array([quat_copr_at_idx]).T,
np.array([chiB_at_idx]).T,
inverse=1).T[0]
# get coorbital frame spins at idx
chiA_at_idx_coorb = utils.rotate_in_plane(chiA_at_idx_copr, phi_at_idx)
chiB_at_idx_coorb = utils.rotate_in_plane(chiB_at_idx_copr, phi_at_idx)
return chiA_at_idx_coorb, chiB_at_idx_coorb, quat_copr_at_idx, \
phi_at_idx, omega_at_idx
def _evolve_spins(self, q, chiA0, chiB0, omega0, \
return_spin_evolution=False, **kwargs):
""" Evolves spins of the component BHs from an initial orbital
frequency = omega0 until t=-100 M from the peak of the waveform. If
omega0 < omega_switch_IG, use PN to evolve the spins until
t=t_sur_switch. Then evolves further with the NRSur7dq4 waveform model
until t=-100M from the peak.
Returns spins in the coorbital frame at t=-100M, as well as the
coprecessing frame quaternion and orbital phase in the coprecessing
frame at this time.
If return_spin_evolution is given, also returns the PN and surrogate
spin times series.
"""
PN_approximant = kwargs.pop('PN_approximant', 'SpinTaylorT4')
PN_dt = kwargs.pop('PN_dt', 0.1)
PN_spin_order = kwargs.pop('PN_spin_order', 7)
PN_phase_order = kwargs.pop('PN_phase_order', 7)
# Initial guess for surrogate omega0, this should be large enough for
# all q=6 cases
omega_switch_IG = kwargs.pop('omega_switch_IG', 0.03)
# The surrogate begins at -4300, use -4100 to be safe
t_sur_switch = kwargs.pop('t_sur_switch', -4100)
self._check_unused_kwargs(kwargs)
# Load NRSur7dq4 if not previously loaded
if self.nrsur is None:
self._load_NRSur7dq4()
# If omega0 is below the NRSur7dq4 initial guess frequency, we use PN
# to evolve the spins. We get the initial spins and omega_init_sur such
# that should go into the surrogate such that the inital time is
# t_sur_switch.
if omega0 < omega_switch_IG:
chiA0_nrsur_coorb, chiB0_nrsur_coorb, quat0_nrsur_copr, \
phi0_nrsur, omega_init_sur, chiA_PN, chiB_PN, omega_PN \
= self._get_PN_spins_at_surrogate_start(PN_approximant, q, \
omega0, chiA0, chiB0, PN_dt, PN_spin_order, PN_phase_order, \
omega_switch_IG, t_sur_switch)
# If omega0 >= omega_switch_IG, we evolve spins directly with NRSur7dq4
# waveform model. We set the coprecessing frame quaternion to identity
# and orbital phase to 0 at omega=omega0, hence the coprecessing frame
# is the same as the inertial frame here.
else:
# Note that here we set omega_init_sur to omega0
chiA0_nrsur_coorb, chiB0_nrsur_coorb, quat0_nrsur_copr, \
phi0_nrsur, omega_init_sur, chiA_PN, chiB_PN, omega_PN \
= chiA0, chiB0, [1,0,0,0], 0, omega0, None, None, None
# Now evaluate the surrogate dynamics using PN spins at omega_init_sur
quat_sur, orbphase_sur, chiA_copr_sur, chiB_copr_sur \
= self.nrsur._sur_dimless.get_dynamics(q, chiA0_nrsur_coorb, \
chiB0_nrsur_coorb, init_quat=quat0_nrsur_copr,
init_orbphase=phi0_nrsur, omega_ref=omega_init_sur)
# get data at time node where remnant fits are done
dyn_times = self.nrsur._sur_dimless.tds
nodeIdx = np.argmin(np.abs(dyn_times - self.fitnode_time))
quat_fitnode = quat_sur.T[nodeIdx]
orbphase_fitnode = orbphase_sur[nodeIdx]
# get coorbital frame spins at the time node
chiA_coorb_fitnode = utils.rotate_in_plane(chiA_copr_sur[nodeIdx],
orbphase_fitnode)
chiB_coorb_fitnode = utils.rotate_in_plane(chiB_copr_sur[nodeIdx],
orbphase_fitnode)
if return_spin_evolution:
# Transform spins to the reference inertial frame
chiA_inertial_sur = utils.transformTimeDependentVector(quat_sur, \
chiA_copr_sur.T).T
chiB_inertial_sur = utils.transformTimeDependentVector(quat_sur, \
chiB_copr_sur.T).T
spin_evolution = {
't_sur': dyn_times,
'chiA_sur': chiA_inertial_sur,
'chiB_sur': chiB_inertial_sur,
'orbphase_sur': orbphase_sur,
'quat_sur': quat_sur,
'omega_PN': omega_PN,
'chiA_PN': chiA_PN,
'chiB_PN': chiB_PN,
'omega_init_sur': omega_init_sur,
}
else:
spin_evolution = None
return chiA_coorb_fitnode, chiB_coorb_fitnode, quat_fitnode, \
orbphase_fitnode, spin_evolution
def _evolve_spins(self, q, chiA0, chiB0, omega0, PN_approximant, PN_dt,
PN_spin0, PN_phase0, omega0_nrsur):
""" Evolves spins of the component BHs from an initial orbital
frequency = omega0 until t=-100 M from the peak of the waveform.
If omega0 < omega0_nrsur, use PN to evolve the spins until
orbital frequency = omega0. Then evolves further with the NRSur7dq2
waveform model until t=-100M from the peak.
Assumes chiA0 and chiB0 are defined in the inertial frame defined
at orbital frequency = omega0 as:
The z-axis is along the Newtonian orbital angular momentum when the
PN orbital frequency = omega0.
The x-axis is along the line of separation from the smaller BH to
the larger BH at this frequency.
The y-axis completes the triad.
Returns spins in the coorbital frame at t=-100M, as well as the
coprecessing frame quaternion and orbital phase in the coprecessing
frame at this time.
"""
if omega0 < omega0_nrsur:
# If omega0 is below the NRSur7dq2 start frequency, we use PN
# to evolve the spins until orbital frequency = omega0_nrsur.
# Note that we update omega0_nrsur here with the PN
# frequency that was closest to the input omega0_nrsur.
chiA0_nrsur_copr, chiB0_nrsur_copr, quat0_nrsur_copr, \
phi0_nrsur, omega0_nrsur \
= evolve_pn_spins(q, chiA0, chiB0, omega0,
omega0_nrsur, approximant=PN_approximant,
dt=PN_dt, spinO=PN_spin0,
phaseO=PN_phase0)
else:
# If omega0>= omega0_nrsur, we evolve spins directly with NRSur7dq2
# waveform model. We set the coprecessing frame quaternion to
# identity and orbital phase to 0 at omega=omega0, hence the
# coprecessing frame is the same as the inertial frame here.
# Note that we update omega0_nrsur here and set it to omega0
chiA0_nrsur_copr, chiB0_nrsur_copr, quat0_nrsur_copr, \
phi0_nrsur, omega0_nrsur \
= chiA0, chiB0, [1,0,0,0], 0, omega0
# Load NRSur7dq2 if needed
if self.nrsur is None:
self._load_NRSur7dq2()
# evaluate NRSur7dq2 dynamics
# We set allow_extrapolation=True always since we test param limits
# independently
quat, orbphase, chiA_copr, chiB_copr = self.nrsur.get_dynamics(
q,
chiA0_nrsur_copr,
chiB0_nrsur_copr,
init_quat=quat0_nrsur_copr,
init_phase=phi0_nrsur,
omega_ref=omega0_nrsur,
allow_extrapolation=True)
# get data at time node where remnant fits are done
fitnode_time = -100
nodeIdx = np.argmin(np.abs(self.nrsur.tds - fitnode_time))
quat_fitnode = quat.T[nodeIdx]
orbphase_fitnode = orbphase[nodeIdx]
# get coorbital frame spins at the time node
chiA_coorb_fitnode = utils.rotate_in_plane(chiA_copr[nodeIdx],
orbphase_fitnode)
chiB_coorb_fitnode = utils.rotate_in_plane(chiB_copr[nodeIdx],
orbphase_fitnode)
return chiA_coorb_fitnode, chiB_coorb_fitnode, quat_fitnode, \
orbphase_fitnode
