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gravitational wave strain

(h, GW strain, strain)
(a measure of the magnitude of a gravitational wave)

A gravitational wave's strain (GW strain, h, or in context, just strain) is a measure of its effect, specifically the ratio by which lengths are stretched or compressed, which is a dimensionless number. The term strain might be used to refer to various particular measures: to the observed strain (as measured by the gravitational-wave detector), or to the strain in the direction of the wave's displacement. Also, the term can be used for the "maximum" strain of the wave (its amplitude), or for the instantaneous displacement (at a point in time). These relations are often cited:

h ≈ ΔL/L
h ≈ ΔT/T

These are sometimes cited with "=" or "∼" instead of "≈", the latter of which is sufficiently loose to be strictly true whether referring to the observed strain or the wave's actual amplitude. The relation based on T represents a shortcut when relative distances are measured by measuring time intervals, such as when using pulsar timing (pulsar timing arrays).

A variant term, characteristic strain (hc), which is sometimes what is intended by strain, is often used in general discussions: it is a kind of averaging (i.e., something like RMS, in that it doesn't merely average to "zero" over each wave period), which includes a component varying by frequency. The term is often used when explaining relative detector ability and source strength over the gravitational wave spectrum.


(physics,measure,gravitational waves,relativity)
Further reading:
https://en.wikipedia.org/wiki/Gravitational_wave
http://www.tapir.caltech.edu/~teviet/Waves/gwave.html
http://www.tapir.caltech.edu/~teviet/Waves/gwave_spectrum.html
https://phys.libretexts.org/Courses/Skidmore_College/Introduction_to_General_Relativity/06%3A_Gravitational_Waves/6.02%3A_Gravitational_Wave_Metric
https://www.physics.usu.edu/Wheeler/GenRel2013/Notes/GravitationalWaves.pdf

Referenced by pages:
gravitational wave (GW)
gravitational wave spectrum
gravitational-wave detector
gravitational-wave memory

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