Home.md

@@ -5,6 +5,25 @@
 > link to out pages.
 
 # Review Statement
+We have reviewed the implementation of a test of general relativity using deviations in the spin-induced quadrupole moment. The method was introduced in Phys. Rev. Lett. 119, 091101(2017), and there was a detailed follow-up in Phys. Rev. D 100, 104019 (2019). 
+
+The review page is here: https://git.ligo.org/nv.krishnendu/lalsuite/-/wikis/home
+
+The inspiral part of lalsimulation waveforms are parameterized in terms of spin-induced quadrupole moments (\kappa_1, \kappa_2) through the post-Newtonian approximation. These spin-induced quadrupole moments characterize the nature of compact objects in the binary. In GR, black holes have \kappa_1 = \kappa_2 =1, however, a black-hole mimicker (e.g., wormholes, garavastar, etc) can have values other than 1. 
+
+This test proposes a null test of BBH nature of a CBC by introducing deviations from the black hole value as, \kappa_1= 1+\delta \kappa_1 and \kappa_2=1+\delta\kappa_2. Using LALInference the pipeline produces posterior distributions on \delta \kappa_1, \delta \kappa_2 and their symmetric combinations \delta \kappa_s and \delta \kappa_a. In GR, for black holes \delta \kappa_1=0 and \delta \kappa_2=0. Hence, if GR is correct, we expect the posteriors on the deviations to be consistent with zero.
+
+We have done a line-by-line code review here: https://git.ligo.org/nv.krishnendu/lalsuite/-/wikis/Code-review
+
+We have reviewed results from the analysis on O1 and O2 events. The results are consistent with the ones in Phys. Rev. D 100, 104019 (2019) and have been understood. The results are summarized here: https://git.ligo.org/nv.krishnendu/lalsuite/-/wikis/Results-review#real-data
+
+We have also reviewed the effect of upper cut-off frequency, spin-magnitude, spin-orientation, mass-ratio and signal-to-noise-ratio on the posterior distribution of \delta \kappa_1 and \delta \kappa_2 (or \delta \kappa_s and \delta \kappa_a). We use simulated signals for this study which are modelled using IMRPhenomPv2 approximant. The results are as expected and are summarized here: https://git.ligo.org/nv.krishnendu/lalsuite/-/wikis/Results-review#injections
+
+We highlight a couple of points which were outside the scope of the review, given the timeline for the exceptional events:
+Noise systematics study for a population: We are satisfied with the code/pipeline for the purpose of analysis on a single event, like GW190814. However, for the purpose of combining results, as might be the case of the O3a TGR paper, we would also like to see results from a noise systematics study (and a corresponding pp-plot). This study is currently being undertaken: https://git.ligo.org/nv.krishnendu/lalsuite/-/wikis/Systematics-Studies
+Waveform systematics study: This test also is implemented for the phenom family of waveforms, and we strongly encourage a test of the waveform systematics by considering injections with different approximants and recovering with the above pipeline. 
+
+Barring these two pending investigations, we are happy to sign off on the code for production of results for GW190814.
 
 # Introduction
 - Spinning compact objects get deformed due to their own spins leading to quadrupole and higher multipole moments. These moments get encoded in the post-Newtonian gravitational waveforms through the spin terms at different PN orders. In the state of art PN spinning waveform, Spin-induced quadrupole appears at 2PN and 3PN in LALSimulation. If the compact object is a BH, the multipole moments should be given by no-hair conjecture. Hence by accurately measuring this effect, we can test whether the high mass compact binaries we have detected so far are indeed BHs and hence constrain the allowed parameter space for BH mimickers. [Here is the Wiki page](https://www.lsc-group.phys.uwm.edu/ligovirgo/cbcnote/TestingGR/O2/SpinInducedQuadrupole/).