Sean Carroll in Cosmic Variance had a posting related to the low entropy of the universe at big bang. The posting is motivated by a criticism of Carroll's own views. Carroll believes that the low entropy of the very early universe is a problem and that the notion of multiverse somehow resolves it. Carroll has naive view about evolution of universe: just Hamiltonian and unitary time evolution and that's all. No questions about problems with general coordinate invariance and symmetries.
Carroll has developed a rhetoric Occam's razor argument about simplicity of theory. Even lawyer would admire it. Since multiverse interpretation does not involve wave function "collapse" ("":s are due to Carroll) it is simpler as a theory and we have a good reason to accept it. I have learned that a standard manner to build a simple theory is to throw out those things which are difficult to understand. Biology, neuroscience, and consciousness belong to this unlucky stuff in recent day theoretical physics.
Lubos comments the posting of Carroll. Lubos does not see anything problematic in the low entropy of the very early Universe. Second law forces it by definition. Lubos in his characteristic manner takes the recent thermodynamics as the final word of science and concludes that Carroll and everyone disagreeing with him does not understand thermodynamics and is pseudo-scientist.
Second issue discussed is the notion of multiverse and many worlds interpretation of quantum mechanics. Carroll assumes cosmological multiverse in his argument for the low entropy as well as the closely related anthropic principle needed to make at least some sense of multiverse. Lubos believes in multiverse because he believes on inflation (and M-theory!). Lubos does not believe in many worlds interpretation since he does not believe that Schrödinger amplitudes - or more generally quantum states- are "real". I would justify my disbelief on Everett interpretation by simple fact that the multiverse poetry about splitting quantum states to my best understanding does not have any translation to any existing mathematics. This does not however require giving up the notion of quantum state if one is ready to return to the roots and make questions about the nature of time.
Discussion revolves among many notions and to my opinion a lot of assumptions leading to the recent crisis remain implicit in the discussion. It is amusing to see that most problems relate to uncritical belief of the theoretical paradigms created during last decades and to notions which should be challenged. Thefatal turning point was probably the introduction of GUTs for four decades ago bringing in untestable assumptions (such as extension of gauge group). Inflationary scenario is highly hypothetical scenario leading to the multiverse. A further hypothetical element is standard view about SUSY. And finally the landscape summarizing the outcome of super string models.
In the following I summarize TGD point of view on the issues discussed. I hope that reader has familiarity with TGD.
Challenging the status of QFT
Both Carroll and Lubos take QFT approach as granted when one talks about low energy physics. TGD forces to modify this view dramatically.
- The notion of many-sheeted space-time and the reduction of the dynamics of classical fields to the dynamics of preferred extremals of Kähler action (just four field like variables, I could say something about simplicity here!). The notion of many-sheeted space-time allows to circumvent the basic objection stating that one cannot have a linear superposition of various fields independently, not even for single field. The point is that only the effects - classically forces - caused by the fields superpose. Particles can have topological sum contacts to large number of space-time sheets and thus they experience superpositions of corresponding forces. This modifies profoundly the existing view. Even the description of Maxwellian fields created by current distribution can be translated to a many-sheeted description by replacing the sum of nearby and radiation fields with a union distinct space-time sheets.
- This means giving up the standard view that some GUT with a huge number of field variables describes the low energy limit of THE theory. This picture is just wrong if TGD is correct and I believe that Occam favors TGD. GUTs are also responsible for the many difficulties in theoretical particle physics and cosmology. Standard SUSY is be replaced with something dramatically simpler and having very different physical interpretation. In this framework it is difficult to imagine that the whole CERN would be trying to identify the point of a very high-dimensional parameter space at which the Universe is believed to be lurking. It is strange that SUSY enthusiasts do not realize that just ending up on this situation tells that something must be wrong. Same applies of course to landscapeologists.
Views about quantum theory is
Also the view what quantum theory is must be modified in TGD framework. The original motivation was simple: the path integral approach simply failed in TGD context.
- TGD leads to a generalization of Einstein's geometrization program for classical fields. Entire quantum theory must be geometrized in terms of the Kähler geometry of "world of classical worlds" (WCW). Quantum states are interpreted as classical spinor fields in the "world of classical worlds" (WCW). These geometric generalizations of Schrödinger amplitudes are definitely something very real so that I am forced to disagree with Copenhagen interpretation and Lubos. This also leads to a beautiful geometrizaton of fermionic statistics in terms of Clifford algebra of WCW and to "quantization without quantization". At space-time level one has free induced spinor fields and quantization for these. Bosonic emergence means that all states are obtained by using fermions as building bricks. This is also an enormous simplification and if this picture is correct, the standard QFT limit need not have much sense except as approximate description.
- Zero energy ontology (ZEO) in which quantum can be seen as a square root of thermodynamics. Quantum states are characterized by entanglement between positive and negative energy parts of zero energy parts and they form what could be seen as a complex square root of density matrix. In this framework "unitary time evolution generated by Hamiltonian" assumed by Carroll is hopelessly simplistic and simply wrong view about the real physical situation. In the p-adic context the the notion of unitary time evolution generated by Hamiltonian is simply non-sense. Zero energy ontology has powerful implications for the notion of Feynman diagrams which are topologized and geometrized. In particular, finiteness of the amplitudes is manifest since also virtual particles consist of massless on mass shell wormhole throats. There are also intriguing connections to the twistor approach.
- TGD based view about quantum jump and state function reduction and extension of physics to a theory of consciousness.The new view about the relationship of experienced time and geometric time however allows to have also the notion of quantum jump without logical contradictions, and one can resolve the basic paradox of quantum measurement theory without giving up the notion of objective reality but replacing it with quantum universe recreated in each quantum jump. Free will and consciousness have place in the theory.
Understanding the anatomy of quantum jumps in ZEO leads to a new view about U-matrix, M-matrix and S-matrix and the resulting picture is extremely simple. U-matrix relates two state basis prepared with respect to either light-like boundary of CD. Time evolution by quantum jumps means sequences of reduction with respect to these two state basis: time flip-flow might be the proper term. Quantum classical corresponds can be used to argue that at space-time level given system is not able to detect the change of the arrow of imbedding space geometric time in this alternating sequence of state function reductions.
Negentropy Maximization Principle the fundamental principle of consciousness theory generalizing quantum measurement theory implies second law in a generalized form required by ZEO, new view about time, and new view about entanglement due to the possibility of p-adic physics identified as physics of cognition.
Generalization of thermodynamics
The generalization of thermodynamics implied by TGD means strong deviations from the naive belief of Lubos that there is nothing to add to what Boltzmann gave to us.
- This includes the definition of entropy in ZEO as a scale dependent notion. This is very relevant when one wants to speak about entropy in cosmological context: entropy characterizes zero energy state and therefore corresponding CD rather than time=constant snapshot of cosmology.
- The distinction between subjective time and geometric time demonstrates that many problems of cosmology related to entropy are pseudo problems. Big Bang is temporal boundary, not a moment of creation: quantum jumps are moments of re-creation and can be localized to any CD anywhere in the imbedding space. One should not assign "before" and "after" to geometric time. Colleagues still refuse to consider seriously the possibility that subjective time and geometric might be different although the debate between Bohr and Einstein revolved around this difference (about which neither of them was aware). Presumably the materialistic dogma is the basic explanation for this short sightedness.
- Second law holds true but the reversal of the arrow of geometric time is possible at imbedding space level: phase conjugate laser beams and many self-organization processes in biology would represent natural candidates in this respect.
- Genuinely negentropic entanglement stable with respect to Negentropy Maximization Principle (NMP) is possible. Negentropic entanglement is the main characterizer of what it is to be living, and space-time correlates of thermodynamics discussed in earlier posting.
TGD analogs for multiverse and inflation
The notion of many words, multiverse and landscape have analogies in TGD Universe but there is nothing problematic in these concepts.
- Many world view corresponds to the identification of WCW spinor fields as quantum superpositions of 3-surfaces allowing by holography an interpretations superposition of 4-surfaces. There is however no need to assume the mysterious repeated splitting of the quantum states.
- The huge vacuum degeneracy of Kähler action implying 4-D spin glass degeneracy something analogous to multiverse mathematically but free of interpretational difficulties. The non-quantum fluctuating variables - zero modes - include the induced Kähler field with completely well-defined physical interpretation, and serve as macroscopic classical variables essential in quantum measurement theory.
- In M-theory spontaneous compactification is needed to get something which could be called physically sensible theory. This leads to the landscape catastrophe spoiling completely the original idea that the dynamics of strings gives gravitation by bringing in gravitational fields as dynamical quantites at target space level. Imbedding space is not dynamical in TGD Universe. This saves from the landscape. Imbedding space is fixed by standard model quantum numbers and the conjecture is that it imbedding space is unique just from the mathematical existence of WCW and has number theoretic interpretation. Already in loop spaces Kähler geometry is unique and requires maximal Kac-Moody symmetry algebra.
- Both Lubos and Carroll believe in inflation in turn leading to multiverse. Inflationary scenario is however highly speculative and plagued by numerous difficulties. The recent findings challenging the notion of galactic halo of dark matter, do not help in this respect and again one must ask is the whole approach wrong in some manner.
In TGD framework there is no inflation. The critical Robertson-Walker cosmologies are unique apart from their duration and correspond to accelerating expansion due to a negative pressure term. Cosmic string explain acceleration expansion at more microscopic level. Cosmic strings dominate during primordial cosmology. Later they expand and give rise to cosmic magnetic fields. They also decay to ordinary matter and dark matter so that the inflaton field is eliminated as so many other fields. Their magnetic tension is responsible for the negative pressure term in the long length scale description in terms of Robertson Walker cosmology. Their magnetic energy corresponds to dark energy.