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TeXify meaure_eccentricity tref_in/fref_in
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md-arif-shaikh committed May 2, 2023
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82 changes: 47 additions & 35 deletions gw_eccentricity/gw_eccentricity.py
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Expand Up @@ -66,51 +66,63 @@ def measure_eccentricity(tref_in=None,
extra_kwargs=None):
"""Measure eccentricity and mean anomaly from a gravitational waveform.
Eccentricity is measured using the GW frequency omega22(t) =
dphi22(t)/dt, where phi22(t) is the phase of the (2, 2) waveform
mode. We currently only allow time-domain, nonprecessing waveforms. We
evaluate omega22(t) at pericenter times, t_pericenters, and build a
spline interpolant omega22_pericenters(t) using those data
points. Similarly, we build omega22_apocenters(t) using omega22(t) at
the apocenter times, t_apocenters.
Using omega22_pericenters(t) and omega22_apocenters(t), we first
compute e_omega22(t), as described in Eq.(4) of arXiv:2302.11257. We
then use e_omega22(t) to compute the eccentricity egw(t) using Eq.(8)
of arXiv:2302.11257. Mean anomaly is defined using t_pericenters, as
described in Eq.(10) of arXiv:2302.11257.
To find t_pericenters/t_apocenters, one can look for extrema in different
waveform data, like omega22(t) or Amp22(t), the amplitude of the (2, 2)
mode. Pericenters correspond to the local maxima, while apocenters
correspond to the local minima in the data. The method option
Eccentricity is measured using the GW frequency :math:`\\omega_{22}(t) =
\\frac{d\\phi_{22}(t)}{dt}`, where :math:`\\phi_{22}(t)` is the phase of
the :math:`(2, 2)` waveform mode. We currently only allow time-domain,
nonprecessing waveforms. We evaluate :math:`\\omega_{22}(t)` at pericenter
times, :math:`t^{\\text{pericenters}}`, and build a spline interpolant
:math:`\\omega_{22}^{\\text{pericenters}}(t)` using those data
points. Similarly, we build :math:`\\omega_{22}^{\\text{apocenters}}(t)`
using :math:`\\omega_{22}(t)` at the apocenter times,
:math:`t^{\\text{apocenters}}`.
Using :math:`\\omega_{22}^{\\text{pericenters}}(t)` and
:math:`\\omega_{22}^{\\text{apocenters}}(t)`, we first compute
:math:`e_{\\omega_{22}}(t)`, as described in Eq.(4) of
`arXiv:2302.11257`_. We then use :math:`e_{\\omega_{22}}(t)` to compute the
eccentricity :math:`e_{\\text{gw}}` using Eq.(8) of
`arXiv:2302.11257`_. Mean anomaly :math:`l_{\\text{gw}}` is defined using
:math:`t^{\\text{pericenters}}`, as described in Eq.(10) of
`arXiv:2302.11257`_.
To find :math:`t^{\\text{pericenters}}`/:math:`t^{\\text{apocenters}}`, one
can look for extrema in different waveform data, like
:math:`\\omega_{22}(t)` or :math:`A_{22}(t)`, the amplitude of the
:math:`(2, 2)` mode. Pericenters correspond to the local maxima, while
apocenters correspond to the local minima in the data. The method option
(described below) lets the user pick which waveform data to use to find
t_pericenters/t_apocenters.
:math:`t^{\\text{pericenters}}`/:math:`t^{\\text{apocenters}}`.
.. _arXiv:2302.11257: https://arxiv.org/abs/2302.11257
Parameters
----------
tref_in
tref_in : float or array_like
Input reference time at which to measure eccentricity and mean anomaly.
Can be a single float or an array.
fref_in
fref_in : float or array_like
Input reference GW frequency at which to measure the eccentricity and
mean anomaly. Can be a single float or an array. Only one of
tref_in/fref_in should be provided.
mean anomaly. Only one of `tref_in`/`fref_in` should be provided.
Given an `fref_in`, we find the corresponding `tref_in` such that
.. math::
\\omega_{22}^{\\text{average}}(t^{\\text{ref}}_{\\text{in}})
= 2 \\pi f^{\\text{ref}}_{\\text{in}}
Given an fref_in, we find the corresponding tref_in such that
omega22_average(tref_in) = 2 * pi * fref_in. Here, omega22_average(t)
is a monotonically increasing average frequency obtained from the
instantaneous omega22(t). omega22_average(t) defaults to the orbit
averaged omega22, but other options are available (see
omega22_averaging_method below).
Here, :math:`\\omega_{22}^{\\text{average}}(t)` is a monotonically
increasing average frequency obtained from the instantaneous
:math:`\\omega_{22}(t)`. :math:`\\omega_{22}^{\\text{average}}(t)`
defaults to the orbit averaged :math:`\\omega_{22}(t)`, but other
options are available (see `omega22_averaging_method` below).
Eccentricity and mean anomaly measurements are returned on a subset of
tref_in/fref_in, called tref_out/fref_out, which are described below.
If dataDict is provided in dimensionless units, tref_in should be in
units of M and fref_in should be in units of cycles/M. If dataDict is
provided in MKS units, t_ref should be in seconds and fref_in should be
in Hz.
`tref_in`/`fref_in`, called `tref_out`/`fref_out`, which are described
below. If `dataDict` is provided in dimensionless units, `tref_in`
should be in units of :math:`M` and `fref_in` should be in units of
cycles/:math:`M`. If `dataDict` is provided in MKS units, `t_ref`
should be in seconds and `fref_in` should be in Hz.
method : str, default: ``Amplitude``
Which waveform data to use for finding extrema. Options are:
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