Is LIGO able to detect the memory effect of gravitational waves? Recently some articles in popular media1, 2 informed that LIGO will be able to measure the memory effect of gravitational waves described by Demetrios Christodoulou in 1991.3
The measurement method based on accumulation over many LIGO measurements was proposed by Paul D. Lasky and colleagues.4
I do not understand most of the details in the paper4 but a mystery for me is how do they count with the effect of gravitational waves which are out of measurement range of LIGO (either by frequency or amplitude). I think we cannot make many assumptions about such waves. Is the paper4 reasonable?


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*Charles Q. Choi "Gravitational Waves May Permanently Alter Spacetime"

*"Advanced LIGO Gravitational Wave Observatory Could Detect Permanent Memory of Spacetime"

*D. Christodoulou (1991). "Nonlinear nature of gravitation and gravitational-wave experiments". Phys. Rev. Lett. 67 (12): 1486–1489.

*Paul D. Lasky, Eric Thrane, Yuri Levin, Jonathan Blackman, Yanbei Chen (2016). "Detecting gravitational-wave memory with LIGO: implications of GW150914"
 A: The BMS (Bondi Metzner, Sachs) symmetry is a semi-direct product of the Poincare group of spacetime symmetry with an abelian group of translations. It is this latter part which contains gravitational memory. This paper illustrates some of this physics. What this means is that a gravitational wave interacting with a set of test masses will not return these masses to their original positions. This does mean the flat spacetime before and after a gravitational wave has passed through are not identical, but related to each other by this abelian translation of points.
The LISA will be able to detect gravitational memory. This is a triplet of satellites that have a their optics on strict geodesic paths. The spacecraft makes orbital adjustments to insure there are no forces on the actual optics. The optical configuration will change with the abelian translation of points. The LIGO by way of contrast has material stresses or strains that return the Michelson-Morely interferometer to its original configuration. This makes testing for gravitational memory, these abelian translations, more difficult. It is however, not entirely impossible. If the material response of the interferometry can be understood well enough, then there maybe characteristics of these abelian translations in the signature of a gravitational wave.
A: The recent arXiv paper "Detection of the Permanent Strain Offset Component of
Gravitational-Wave Memory in Black Hole Mergers" by Jeff Scargle, using LIGO data, claims to have detected for the first time the effect of Gravitational Wave Memory.
