Saturday, October 21, 2017

Some comments about GW170817

The observation of GW170817 was perhaps the event of the year in astronomy. Both gravitational waves and electromagnetic radiation from the collision of two neutron stars fusing to single object were detected. The event occurred at distance of order 130 Mly (size scale of large voids). This was a treasure trove of information.

The first piece of information relates to the question about the synthesis of elements heavier than Fe. It is l assumed that the heavier elements are generated in so called r-process involving creation of neutrons fusing with nuclei. One option is that the r-process accompanies supernova explosions but SN1987A did not provide support for this hypothesis: the characteristic em radiation accompanying r-process was not detected. GW170817 generated also em radiation, so called kilonova (see this), and the em radiation accompanying r-process was reported. Therefore this kind of collisions would generate at least part of the heavier elements. In TGD framework also so called dark nucleosynthesis occurring outside stellar interiors and explaining so called nuclear transmutations, which are now rather well-established phenomenon, would also contribute to he generation of heavier elements (and also the lighter ones) (see this).

Second piece of information was that in GW170817 both gravitational waves and gamma ray signal were detected, and the difference between the arrival times was about 1.7 seconds: gamma rays arrived slightly after the gravitational ones. From this the difference between effective propagation velocities between gravitational and em waves is extremely small.

Note that similar difference between neutrino signal and gamma ray signal was measured for SN1987A. Even gamma rays arrived at two separate pulses from SN1987A. In this case the delay was longer and a possible TGD explanation is that the signals arrived along different space-time sheets (one can certainly tailor also other explanations).

  1. In the recent case it would seem and gravitons and photons arrived along the same space-time sheet (magnetic flux tubes) or at least that the difference for effective light velocity was extremely small if the sheets were different. Perhaps this is the case for all exactly massless particles. In the case of SN1987A neutrino burst was observed 3 hours after gamma ray burst.

  2. From the distance of about .17 MLy one can estimate Δ c/c. If Δ c/c has the same value for GW17081, the neutrino burst for it should have arrived after 2846 hours making 118 days (day=24 hours). This would explain why neutrinos were not detected in the case of GW170817. The explanation has been that the direction was such that neutrino pulse was to weak to be detected in that direction. In any case, if colleagues would take TGD seriously, they would be eagerly waiting for the arrival of neutrino pulse!
So called modified gravity theories claim that dark matter and dark energy are not real (for instance MOND suggesting a more or less ad hoc modification of gravitation at very small accelerations and Verlinde's model, which has received a lot of attention recently). Certain class of these models predict a breaking of Equivalence Principle. Gravitons would couple only to the metric created by ordinary matter as predicted by GRT whereas ordinary matter would couple to that created by dark and ordinary matter as predicted by GRT.

Although this kind of models look hopelessly ad hoc (at least to me), they have right to be shown wrong and GW170817 did it (see this). The point is that the coupling to dark matter besides ordinary matter implies that gamma rays experience additional delay and arrive later than gravitons coupling only to the ordinary matter. This causes what is called Shapiro delay of about 1000 days much longer than the observed 1.7 seconds. Thus these models are definitely excluded. I do not know what this means fro MOND and Verlinde's model.

There is an amazing variety of MOND like models there to be killed and another article about what GW170817 managed to do can be found (see this). Theoretical physics is drowning to a flood of ad hoc models: this is true also in particle physics where great narratives have been dead for four decades now. GW170817 looks therefore like a godly intervention similar to what happened with Babel's tower.

There is a popular article titled "Seeing One Example Of Merging Neutron Stars Raises Five Incredible Question" (see this) telling that GW100817 seems to be very badly behaving guy challenging the GRT based models for the collisions of neutron stars. Something very fishy seems to be going on and this might be the change for TGD to challenge GRT based models.

  1. The naive estimate for the rate of these events is 10 times higher than estimated (suggesting that colliding objects were connected by flux tube somewhat like biomolecules making them possible to find each other in the molecular soup).

  2. The mass ejected from the object was much larger than predicted. The signal in UV and optical parts of the spectrum should have lasted about one day. It lasted for two days before getting dimmer.

  3. The final state should have been blackhole or magnetar collapsing rapidly into blackhole. It was however supermassive neutron star with mass about 2.74 solar masses. The upper limit is about 2.5 solar masses for non-rotating neutron star so that the outcome should have been a blackhole without any ejecta!

    TGD view about blackholes differs from that of GRT. The core region of all stars (actually all physical objects including elementary particles) involves a space-time sheet for which the signature of the induced metric is Euclidian. The signature changes at light-like 3-surface somewhat analogous to blackhole horizon. For blackhole like entities there is also Schwartschild horizong above this horizon. Could this model provide a better model for the outcome of the fusion.

  4. Why gamma ray bursts were so strong and in so many directions instead of cone of angular width about 10-15 degrees? Although gamma ray burst was about 30 degrees from the line of sight, it was seen.

    Heavier elements cannot be produced by fusion in stellar interiors since the process requires energy. r-process in the fusions of neutron stars has been proposed as the mechanism, and the radiation spectrum from GW170817 is consistent with this proposal. The so called dark nucleosynthesis proposed in TGD framework to explain nuclear transmutations (or "cold fusion" or low energy nuclear reactions (LENR)) (see this). This mechanism would produce more energy than ordinary nuclear fusion: when dark proton sequence (dark nucleus) transforms to ordinary nucleus almost entire nuclear binding energy is liberated. Could the mechanism producing the heavier elements be dark nuclear fusion also in the fusion of neutron stars. This would have also produced more energy than expected.

See the article LIGO and TGD or the chapter Quantum astrophysics of "Physics in Many-sheeted Space-time".

For a summary of earlier postings see Latest progress in TGD.

Articles and other material related to TGD.

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