Hi Lawrence, First I want to thank you for your highly detailed reply. I have some further comments and questions below, if you don't mind.
On Thu, Oct 15, 2020 at 5:48 AM Lawrence Crowell < [email protected]> wrote: > There is nothing wrong in particular with the idea of fine tuning. This > does not logically imply a fine tuner. If there is a fine tuner, then it is > reasonable to say there is fine tuning. However, the converse or modus > tolens does not hold; fine tuning does not logically imply a fine tuner. > Therefore, fine tuning is a necessary condition of a fine tuner, but not > sufficient. > Towards the end I use fine-tuning, and Bayesian inference to decide the trilemma as defined by Martin Rees: coincidence, providence, or multiverse. Given the appearance of fine tuning, we update our priors and effectively rule out coincidence and providence with high confidence. So we cannot decide there is a fine tuner, but we can be confident in "not coincidence" whose probability is equal to (fine-tuner or multiverse). The article concludes with a decision that both answers imply the existence of something beyond this universe, and quite plausibly the existence of universes of a higher order and complexity than our own, containing entities superior to ourselves. > > I started reading this, but it is clearly not something I am going to > finish over early morning coffee. Yet the article so far covers in layman's > terms stuff I am well acquainted with. The multiverse is often cited as a > way around this. A vast plurality of cosmologies is a way to argue how the > particular observable cosmos is fine tuned. It is similar to the argument > with planets; given a large number of them it is not surprising that a few > are such that life may emerge. Of course with this multiverse I suspect > that many of these are not real cosmologies. > > The cosmological constant for all putative cosmologies in the string > landscape, based on D-brane theory with gauge fluxes through branes wrapped > on Calabi-Yau spaces, have cosmological constants Λ much larger than that > for the observable universe. The Hubble constant H = (a'/a), a the scale > factor and a' = da/dt, also equals H = √(Λc^2/3) is numerically H = > 72km/sec-Mpc and 68km/sec-Mpc, where these two come from galaxy data and > CMB data. This corresponds to a cosmological constant Λ ≃ 10^{-52}m^{-2}. > Most putative cosmologies have much larger values, and many orders of > magnitude larger. Such a de Sitter or FLRW spacetime would expand so > rapidly that nothing could form. In fact many have Λ ≃ 10^{66}m/s^2 with > the upper bound Λ ≃ 10^{70}m/s^2. The difference between this and what we > observe is the 122 order of magnitude issue. > Given the uncertainties around the probability distributions for the other constants of nature, the article uses Λ as the chief variable in deriving the improbability of the tuning. Is there a difference assumed between how Λ emerges in string theory vs. how it is assumed to emerge from quantum field theory? Is it, in both cases, the sum of order-one positive and negative numbers? I have seen some say it is tuned to 60decimal places, and others that it is tuned to 120 decimal places. What accounts for this difference in estimation, is it based on the assumption of supersymmetry? > > The observed cosmological constant is a manifestation of the quantum > vacuum energy density, or in particular that vacuum energy density that > plays a role in gravitation. This vacuum energy ρ defines the cosmological > constant Λ = 8πGρ/3c^3 and for the observable universe this is quite small, > far smaller than the 123 order of magnitude larger figure a naïve summation > of QFT modes would suggest. However, there is a difference between the high > energy vacuum, or called false vacuum, and the low energy physical vacuum. > A quantum tunneling from the false to physical vacuum results in a gap of > mass-energy density in every volume of space, and this generates matter and > radiation. The sort of skewed Ginsburg-Landau potential involved is seen in > the figure below. > [image: quartic asymmetric potential.png] > > This is something I wondered about. Is it assumed that a high Λ (or high vacuum energy) is what powered inflation, and then later this decayed to its much smaller value, which drives a doubling in billions of years rather than in 10^-35 seconds? Wouldn't that require one of the quantum fields to disappear, or at least undergo significant change? > There is a linear term in fields that skews this, and this I think is some > manifestation of renormalization theory, where the large majority of these > are analogous to virtual particles that give a mass-renormalization of > cosmologies. This would I think sweep the vast majority of these out of > ontological existence or classicality. I do not know if this is complete so > there is the reduction of the multiverse to a single universe, or whether > this is a reduction of the multiverse to a much smaller set. > > It has to be noted that the tuning for flat, spherical or hyperbolic > geometry or topology of a spatial surface is not that hard to understand. > The Hamiltonian for the Friedman-Lemaitre-Robertson-Walker (FLRW) spacetime > is > > ℋ = ½(a’/a)^2 - 4πGρ/3c^2 + k/a^2, > > so that the Hamiltonian constraint Nℋ = 0 in ADM general relativity means > it is not hard to see this is zero. The energy density is ρ = ρ_vac + > ρ_energy for the vacuum and mass-energy in the spacetime. The additional > term k/a^2 gives flat, spherical and hyperbolic space for k = 0, k = 1 and > k = -1. If k = 0 then the vacuum energy density is constant. This is in > various ways more reasonable. > > In this renormalization possibility somehow the observable universe may > have emerged. In ways not entirely clear this may have selected the world > we observe. So there are open questions. Maybe even the role of conscious > observers in the universe play some Wheeler delayed choice experiment in > measuring the early universe to select for the observed universe. > I've thought about this with regards to the measurements of the constants. If we imagine measuring constants to more and more decimal places, and get so far along that we reach decimal places no longer significant to fine-tuning or AP, then do we reach a point where we are exploring a random variable and getting back random digits for those constants? (In effect, collapsing them from their prior state of being undetermined). Jason > > LC > > > On Wednesday, October 14, 2020 at 9:38:40 PM UTC-5 Jason wrote: > >> I just finished an article on all the science behind fine-tuning, and how >> the evidence suggests an infinite, and possibly complete reality. I thought >> others on this list might appreciate it: >> https://alwaysasking.com/was-the-universe-made-for-life/ >> >> I welcome any discussion, feedback, or corrections. >> >> Jason >> > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/c67a54a2-64bc-4818-b8d5-c9bcf361940en%40googlegroups.com > <https://groups.google.com/d/msgid/everything-list/c67a54a2-64bc-4818-b8d5-c9bcf361940en%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. 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