When there are numerous overlapping events, it may be difficult to isolate them but together they will combine to give an excess in the power spectrum.

Maria Krikeli

As far as we understand it, gravitational waves are purely additive, they do not 'interfere' and do not form the equivalent of the light and dark bands we see in optics. This means that, given the three satellite configuration is constantly changing relative to the environment, it should be relatively straightforward to phase separate the 'signals' and hence identify the direction of any specific gravitational source.

Dear Maria,

Sorry, I missed part of your question.

MK: How do we know that our observing signal is coming from a source in the Early Universe and not, from two combined gravitational waves, in a distance closer to us (for example a gravitational wave from a BHBH collision and the other one from a NSNS collision )?

SEG: Personally I don’t think that LIGO has detected gravitational waves in the sense of Newtonian gravity. Because Newtonian gravity emerges when rest mass is created. Thus Newtonian gravity represents the vectorized scalar field in vacuum space and its influence is instantaneous ...

That is correct, the waves that LIGO can detect do not exist in Newtonian gravity and any scalar variation travelling instantaneously would affect both arms identically and simultaneously so there would be no output from the interferometer which is inherently a differential instrument.

The waves they see are however exactly as predicted by GR to the accuracy achieved so far.

The wave equation has more solutions than waves and wave packages. It also supports shock waves. During travel, all shock waves keep the shape of the front. That is why the response to a big explosion after billions of years still leads to a front passage of a few seconds. The amplitude of the front diminishes as 1/r with distance r. That means that the very high amplitude immediately after the explosion reduced to very tiny value when it was detected by LIGO and Virgo. The difference in the length of the two 4 km arms that were traveled ten times by light was a fraction of the diameter of the nucleus of an atom.

Shock fronts play an important role in physics. Already point-like artifacts can produce them. However, these tiny field excitations cannot be detected by instruments. In huge quantities the point-like artifacts can produce noticeable effects.

See: Mass: http://dx.doi.org/10.13140/RG.2.2.10268.59528

Dear Maria Krikeli, this problem is very difficult, because we live now in the modern Universe. We cannot know exactly the structure of Early Universe. Gravitation and gravitational waves (non-stationary gravitational fields) are connected with the structure of the Time. We must consider the Time not only as a coordinate: it is connected immediately with the masses of the body of the Universe and masses different parts of the Universe (stars, galaxies,...) The kind of gravitation is determined by the form of gravitating body, its mass and radius. We do not know the structure of the Early Universe, therefore we can find only wave, which are radiated by modern cosmic bodies (neutron stars, for example).

Maria,

A spherical shock wave is a pulse response. The front contains volume that spreads with the surface of the sphere. The pulse injected the volume into the field and this volume deforms the field locally. The deformation is temporarily because the volume spreads over the full field. Consequently it expands the field. The field represents the universe and the spherical pulse response of a point-like actuator forms the germ of gravitation. The effect is so tiny that no instrument will ever be capable of detecting it. To get a significant and persistent deformation a mechanism must create a huge and coherent swarm of pulses. The swarm must be dense enough and the regeneration cycle must be short enough. This happens for the private mechanism that supports an elementary particle. The location density distribution of the swarm equals the squared modulus of the wavefunction of the particle.

The gravitation "wave" that is detected by LIGO and Virgo is generated by a huge explosion that lasted very shortly. The shock front kept its shape, such that after a trip of many millions of light years the front passed in the same short time frame. The huge amplitude at the explosion diminished as 1/r over the huge distance. That is why the amplitude was hardly measurable. A difference in length of parts of the diameter of the nucleus of an atom was measured between two 4 km pipes that each were traveled ten times. A very precise measurement!

The gravitation "wave" was a front and no wave package. During travel wave packages disperse. This front did not disperse. It kept its shape during a very long travel.

Dear Maria, i think, it is possible to consider analogies between structures of non-stationary neutron stars and body of the Universe. This analogies are showed in the book Larissa Borissova and Dmitri Rabounski "Inside stars", 2013. It is in Inet for free reading. We have obtained that these stars and the Universe possess equal physic and geometric properties. We found that these structures possess the same non-Newtonian force of repulsion. We obtained that there exist two types of stars (as neutron and as the Sun and others usual stars). Theirs structure is determined by gravitation. Inside usual stars acts force of attraction. I continue this work? see

http://geocities.ws/borissova/

With best wishes, Larissa

Hi Maria,

MK: I was wondering if detecting a gravitational wave from a collision of population III stars we could figure out the structure of the Early Universe.

Pop III stars are expected to be very large, possible up to 300 MSun, due to their low metallicity. As binary system, mass transfer might cause one to end as a supernova before they reached the contact binary stage. Even then, their separation would be such that their orbital period would be quite long and the GW radiation very weak as a result. GW are best produced from very compact objects. You could get a rough idea of the expected GW frequency by applying Kepler's Laws to the orbits of a pair of such large stars (then double it). If eLISA is launched, it might be able to detect mergers but mass transfer may remove them as a potential source.

Single Pop III stars have the ability to collapse directly to black holes at the end of their life, that may be the origin of the very high mass BH mergers that LIGO has already seen. There's a paper on that here:

Article Gravitational Wave Sources from Pop III Stars are Preferenti...

Regarding the early universe, I think we would be able to use these events to study the distribution of Pop III star forming regions.

The comments from Hans are very misleading.

HvL: The gravitation "wave" that is detected by LIGO and Virgo is generated by a huge explosion that lasted very shortly.

That is not true, the waves that LIGO detects come predominantly from the inspiralling orbits prior to contact. In the case of GW170817, LIGO observed around 3000 cycles of the waves corresponding to 1500 complete orbits of the binary system.

Explosions are not expected to produce a gravitational disturbance due to Birkhoff's Theorem. Any small signal would need to be due to an asymmetric detonation and would not be cyclical so would be indistinguishable from noise in the LIGO detector.

Dear Maria,

While these remnants may be common in the centre, it's not clear that they can merge to form SMBH, the origin of those is still unclear.

Regarding stability, the IMF is due to the low metallicity and their lifetime is very short as a resul. They can collapse directly to black holes or be disrupted, see for example Figure 2 in this paper:

Article Evolution of Massive Population III Stars

You may find this of interest too:

http://iopscience.iop.org/article/10.1088/0004-637X/792/1/44/pdf

This is older (2004) but predicts an earlier formation of the first stars, around z=65, which gives some concern that the financial cuts the the JWST may have put these out of reach. The original design targetted z=25 but the revision brought that down to z=15.

Article The First Stars in The Universe

My question is, we have never seen any black hole, and we know wave can not be created in absolute zero temp. between galaxies. How that possible the wave come from crashing two black hole, through absolute zero temperature form 1.1 billion of light years from other galaxies? The LIGO Wave must be something else, not gravitational wave.