Monday, September 22, 2014

Why I keep my mind open concerning BICEP2 findings?

Some time ago BICEP2 published an eprint, which became the scientific news of year. They claimed that cosmic microwave background (CMB) exhibits co called B modes with a local polarization, which is rotational ("whirly"), and would be caused by primordial gravitational waves during the inflationary period. I discussed the finding from TGD point of view here.

Inflation theorists interpreted this as a support for inflation although the size of the effect was so large that quantum field theoretic modelling in terms of inflaton concept (analogous to Higgs) becomes highly questionable mathematically. Soon the finding of BICEP2 was challenged (I wrote about this here) . Later BICEP2 published an article in which they admitted that the effect could be due to the dust. Planck collaboration published now an eprint supporting the view that the signal observed by BICEP2 is probably due to dust.

The effect forced to develop in more detail the TGD view about the transition from primordial cosmic string dominated cosmology (gas of cosmic strings) to radiation dominated cosmology. TGD view forces to leave the world as quantum field theories (QFTs) general relativity see it. Primordial cosmology would correspond to tring gas dominated phase in which standard view about space-time does not make sense. The counterpart of inflationary period would correspond to a transition to radiation dominated phase in which the space-time sheets - slightly curved pieces of Minkowski space - make sense and GRT limit of TGD obtained by replacing the space-time sheets of many-sheeted space-time with single slightly curved piece of M4 is practical and many-sheetedness makes it manifest only via anomalies. In GRT framework the gas of cosmic strings does not make sense and inflationary period in which space-time sheets already appear is a bridge to the world, where GRT space-time is a useful concept.

This transition is phase transition and quantum criticality fixes the cosmology during this period completely apart from the duration of the period. The curvature scalar of 3-space vanishes (no scales at quantum criticality) as it does also in inflationary cosmology. Hence it should not be surprising (it was!) that the outcome were very similar to that in inflationary cosmology: accelerated expansion. This period must have finite duration as it has because otherwise the mass density would become literally infinite, which is not possible since the density of cosmic strings in "vapour phase" is finite.

Unlike the purely phenomenological QFT mode involving inflaton type fields, TGD provides a detailed geometric mechanism for the generation of the CMB polarization in terms of magnetic flux tubes. I cannot however calculate the size of the effect, and one can also imagine effect caused by the presence of the magnetic flux tubes and it could contribute also at later times.

Lubos has a very interesting posting emphasizing the David-Goliath setting: big and arrogant Planck against tiny Bicep2! On basis of my own frustrating experiences as tiny David I am forced to take this sociological interpretation seriously.

Lubos argues that the whirling pattern observed for the polarisation direction vector is regular and exhibits a definite scale. One can argue that dust - if it it is dust - would produce a random pattern. Personally I do not have any strong attitudes pro or con: TGD predicts primordial gravitational waves but I am unable to calculate the magnitude of the effect. TGD also suggests aan alternative mechanism producing the whirling: it could be due to rotational magnetic fields at magnetic flux tubes (having cosmic strings as predecessors) - that is vectorial rather than tensorial effect. This effect could be present also at later times and produce regular whirling pattern.

Magnetic fields are indeed known to exist in arbitrary long astrophysical and cosmological scales. This is one of the big challenges of cosmology since their presence requires currents but in cosmology thermodynamical equilibrium does not allow this kind of currents in long length scales. In TGD framework (due to the topology of CP2) the flux tubes carry monopole fluxes requiring no currents, and in the first approximation these fields can be locally irrotational although they have closed flux lines. A flow around an annulus in plane illustrates this: the flow can ge locally irrotational everywhere but obviously there is a global rotation. Does local irrotational character of these magnetic fields imply that local polarization of CMB cannot be generated by closed flux tubes? Or does the whirling pattern make the web of flux tubes directly visible?

Average blogger is quite too hasty in putting BICEP2 findings to the same category as the "discovery" that neutrinos travel with a speed slightly higher than photons (doing this with emotional rhetorics is an easy manner to increase the number of visitors!). Ironically, supernova SN1987 demonstrated for 27 years that neutrinos indeed seem to move faster than photons! The neutrinos from SN1987 came in two groups and both neutrino bursts came earlier than the gamma ray burst. TGD explanation is that the the neutrinos bursts and potons arrived along different space-time sheets with slightly different arrival times meaning Δc/c ∼ 10-9. The effect claimed by the OPERA collaboration would have been much larger, something like Δc/c ∼ 10-5.

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