scri.pn.boosted_comcharge

Functions

`PN_charges`(m, ν)	Determine a tuple of callables for a specific input of mass (m) and symmetric mass ratio (ν).
`analytical_CoM_func`(θ, t, E, J_mag, G_mag, ψ)	Compute a model time series for boosted center-of-mass (CoM) charge using PN expressions of energy, angular momentum, and CoM charge, along with the phase computed from the h_{21} mode.

scri.pn.boosted_comcharge.PN_charges(m, ν)[source]

Determine a tuple of callables for a specific input of mass (m) and symmetric mass ratio (ν).

Parameters:

m: float, real: Total mass of the binary.
ν: float, real: Symmetric mass ratio of the binary.

Returns:

energy_pncallable: Returns PN approximation for energy up to 2PN order
angular_momentum_pncallable: Returns PN approximation for angular momentum up to 3PN order
G_mag_pncallable: Returns PN approximation for the magnitude of CoM charge up to leading PN order
orbital_phasecallable: Returns the orbital phase from the (2,1) mode of the strain. See notes for convention used.
All returned callables accept an ABD object as an input
parameter and return their respective quantities evaluated at the
same time steps as the ABD object. The PN expressions for
energy and angular momentum are taken from Eqs. (337) and (338) of
Blanchet’s Living Review (2014) <https://arxiv.org/abs/1310.1528>.
The PN expression for CoM charge is derived in Khairnar et al.
<https://arxiv.org/abs/2603.24661>.
The tuple of these callables can be passed as
the Gargsfun keyword argument to map_to_superrest_frame.
These callables are then used to determine the Gargs parameters to
transformation_from_CoM_charge. They are called as: Gargs = [func(abd) for func in Gargsfun] if Gargsfun else None
within the com_transformation_to_map_to_superrest_frame
function.

Notes

Our conventions for defining the orbital phase differ from the standard conventions used in PN theory. This stems from the fact that SpEC uses h_{ab} to define the metric perturbation while PN theory uses h^{ab} for the metric perturbation, which results in h^{PN}_{l,m} = − h^{NR}_{l,m}. The leading order PN expression for the h_{2,1} mode is (Eq. 492 of <https://arxiv.org/abs/1310.1528>) h^{PN}_{21} = (2 G ν m x)/R * sqrt(16 pi/5) * ((1/3) 𝒾 Δ x^{1/2} + O(x^{3/2})). Because of the 𝒾 factor we get the orbital phase numerically as ψ = - arg(-h^{NR}_{2,1}) + π/2.

scri.pn.boosted_comcharge.analytical_CoM_func(θ, t, E, J_mag, G_mag, ψ)[source]

Compute a model time series for boosted center-of-mass (CoM) charge using PN expressions of energy, angular momentum, and CoM charge, along with the phase computed from the h_{21} mode.

This model timeseries is derived in Khairnar et al. <https://arxiv.org/abs/2603.24661>. It serves as a fitting function that can be passed as the Gfun keyword argument to the map_to_superrest_frame function. All the arguments are computed over the window used for fixing the frame.

Parameters:

θ: ndarray, real, shape(8,): Parameters of the model. - θ[0:3] : components of the boost velocity - θ[3:6] : components of the spatial translation - θ[6:] : two additional fit parameters referred to as the

nuisance parameters in Khairnar et al. <https://arxiv.org/abs/2603.24661>.
t: ndarray, real: Time array corresponding to the window over which the frame fixing is performed.
E: ndarray, real: PN approximation for the energy computed over the fitting window.
J_mag: ndarray, real: PN approximation for the magnitude of angular momentum computed over the fitting window.
G_mag: ndarray, real: PN approximation for the magnitude of the CoM charge computed over the fitting window.
ψ: ndarray, real: Unwrapped orbital phase obtained from the (2,1) mode of the strain over the fitting window. See PN_charges for appropriate conventions.

Returns:

G: ndarray, real, shape(…, 3): Model time series of the boosted center-of-mass charge.