Do gravitational waves add mass to black hole?

Due to the recent discovery of gravitational waves by LIGO I was wondering suppose a black hole stood between a gravitational wave then due to the fact that black hole can attract every thing then would the gravitational wave energy (that was lost from the objects producing the gravitational wave) be deposited inside the black hole?

Or would the gravitational wave simply pass through the black hole?

Finally do gravitional waves "red shift" or "blue shift" due to the gravity of another object?

If we accept that gravity will be successfully quantized, the question can be answered in a similar way as with photons, the gravitational wave emerging from the confluence of gravitons similar to electromagnetic waves emerging from a confluence of photons.

So, depending on the wave length ( the energy of the graviton) and the crossection of graviton-blackhole scattering, some will be trapped within the horizon, contributing to the mass of the black hole, and some will be scattered away from it, depending on angle of incidence and spin quantum numbers.

Or would the gravitational wave simply pass through the black hole?

No. See above.

Finally do gravitional waves "red shift" or "blue shift"? due to the gravity of another object

Yes, similar to photons.

• Why should this have anything to do with quantization? Gravitational waves and black holes can both be described quite well by general relativity. – Peter Shor Oct 9 '16 at 13:11
• @PeterShor just saw this because of a -1. Answering with geodesics is fine, if you can derive the answer. As a particle physicist I can see analogies easily with quantization. Photons get trapped increasing with their enrgy the mass of the black hole, and so would the possible gravitons. It is simpler. – anna v Oct 31 '18 at 4:55

would the gravitational wave energy (that was lost from the objects producing the gravitational wave) be deposited inside the black hole?

At least some of it would. If a gravitational wave is incident on a black hole, then by conservation of energy, the sum of the initial energy of the wave and mass-energy of the black hole is equal to the sum of whatever wave energy is scattered and the final mass-energy of the black hole. (This follows from conservation of the ADM mass, which is conserved in an asymptotically flat spacetime and includes radiation that escapes to future null infinity.)

Or would the gravitational wave simply pass through the black hole?

No, I don't think so. The only way for the black hole not to gain mass would be if 100% of the wave's energy were scattered, and none absorbed, but there is no way that's going to happen.

For instance, consider the (unrealistic) case where the wavelength is small compared to the Schwarzschild radius of the black hole. Then the wave's energy can be localized to a region as small as a wavelength, and therefore when some of this energy, in a region of this size, passes inside the event horizon, it is guaranteed to be absorbed.

The more realistic case would be one in which the wavelength is millions of times bigger than the size of the black hole. I can easily imagine that in a case like this, some much larger fraction $$f$$ of the wave's energy would be scattered, perhaps almost all of it, but this $$f$$ has to be a smooth function of the initial parameters, so I don't see how it can become exactly 1.

Finally do gravitional waves "red shift" or "blue shift" due to the gravity of another object?

Yes, because the standard results for gravitational Doppler shifts depend only on two assumptions: (1) the wave propagates at $$c$$, and (2) the equivalence principle holds. Both of these assumptions are valid here.

First there is a question of size: as for any wave, if the wavelength of the wave is quite larger than the black hole perturbation, it won't even see it.

Otherwise, yes, following the geodesics a section of wave will be channeled on the BH. But why should it bring mass ?

• I would guess that the OP is thinking that the gravitational wave might be absorbed by the black hole, and therefore the energy of the wave would contribute to the black hole's mass. – Brionius Feb 14 '16 at 1:35
• Yep. I don't know how this energy can be absorbed, anyway with the distance + limited cross-section of a blackhole it should be extra-weak. + as I understanding, the emission of these waves is transcient, not regular over million years. – Fabrice NEYRET Feb 14 '16 at 20:21
• Considering Feynman's bead on a string argument described in this answer, it's possible for a thing to extract energy from a gravitational wave. Black holes have a small vocabulary - unless the gravitational waves have vorticity, the only way they will show the energy is in the form of mass. – uhoh Jun 18 '16 at 4:05