On Saturday, September 14, 2019 at 4:34:28 PM UTC-6, Jason wrote: > > > > On Sat, Sep 14, 2019 at 3:06 PM Alan Grayson <agrays...@gmail.com > <javascript:>> wrote: > >> >> >> On Saturday, September 14, 2019 at 7:46:27 AM UTC-6, Jason wrote: >>> >>> >>> >>> On Sat, Sep 14, 2019, 4:36 AM Alan Grayson <agrays...@gmail.com> wrote: >>> >>>> >>>> >>>> On Saturday, September 14, 2019 at 12:34:18 AM UTC-6, Jason wrote: >>>>> >>>>> >>>>> >>>>> On Friday, September 13, 2019, Alan Grayson <agrays...@gmail.com> >>>>> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Friday, September 13, 2019 at 4:42:00 PM UTC-6, Jason wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Fri, Sep 13, 2019 at 8:25 AM Alan Grayson <agrays...@gmail.com> >>>>>>> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Friday, September 13, 2019 at 5:24:11 AM UTC-6, Bruno Marchal >>>>>>>> wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> On 13 Sep 2019, at 04:26, Alan Grayson <agrays...@gmail.com> >>>>>>>>> wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Thursday, September 12, 2019 at 11:01:54 AM UTC-6, Alan Grayson >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> On Thursday, September 12, 2019 at 7:45:22 AM UTC-6, Lawrence >>>>>>>>>> Crowell wrote: >>>>>>>>>>> >>>>>>>>>>> On Thursday, September 12, 2019 at 4:20:46 AM UTC-5, Philip >>>>>>>>>>> Thrift wrote: >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> On Wednesday, September 11, 2019 at 11:45:41 PM UTC-5, Alan >>>>>>>>>>>> Grayson wrote: >>>>>>>>>>>>> >>>>>>>>>>>>> >>>>>>>>>>>>> https://www.wired.com/story/sean-carroll-thinks-we-all-exist-on-multiple-worlds/ >>>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Many Worlds is where people go to escape from one world of >>>>>>>>>>>> quantum-stochastic processes. They are like vampires, but instead >>>>>>>>>>>> of >>>>>>>>>>>> running away from sunbeams, are running away from probabilities. >>>>>>>>>>>> >>>>>>>>>>>> @philipthrift >>>>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> This assessment is not entirely fair. Carroll and Sebens have a >>>>>>>>>>> paper on how supposedly the Born rule can be derived from MWI I >>>>>>>>>>> have yet >>>>>>>>>>> to read their paper, but given the newsiness of this I might get to >>>>>>>>>>> it. One >>>>>>>>>>> advantage that MWI does have is that it splits the world as a sort >>>>>>>>>>> of >>>>>>>>>>> quantum frame dragging that is nonlocal. This nonlocal property >>>>>>>>>>> might be >>>>>>>>>>> useful for working with quantum gravity, >>>>>>>>>>> >>>>>>>>>>> I worked a proof of a theorem, which may not be complete >>>>>>>>>>> unfortunately, where the two sets of quantum interpretations that >>>>>>>>>>> are ψ-epistemic and those that are ψ-ontological are not decidable. >>>>>>>>>>> There >>>>>>>>>>> is no decision procedure which can prove QM holds either way. The >>>>>>>>>>> proof is >>>>>>>>>>> set with nonlocal hidden variables over the projective rays of the >>>>>>>>>>> state >>>>>>>>>>> space. In effect there is an uncertainty in whether the hidden >>>>>>>>>>> variables >>>>>>>>>>> localize extant quantities, say with ψ-ontology, or whether >>>>>>>>>>> this localization is the generation of information in a local >>>>>>>>>>> context from >>>>>>>>>>> quantum nonlocality that is not extant, such as with >>>>>>>>>>> ψ-epistemology. Quantum interprertations are then auxiliary >>>>>>>>>>> physical axioms or postulates. MWI and within the framework of what >>>>>>>>>>> Carrol >>>>>>>>>>> and Sebens has done this is a ψ-ontology, and this defines the >>>>>>>>>>> Born rule. If I am right the degree of ψ-epistemontic nature is >>>>>>>>>>> mixed. So the intriguing question we can address is the nature of >>>>>>>>>>> the Born >>>>>>>>>>> rule and its tie into the auxiliary postulates of quantum >>>>>>>>>>> interpretations. >>>>>>>>>>> Can a similar demonstration be made for the Born rule within >>>>>>>>>>> QuBism, which >>>>>>>>>>> is what might be called the dialectic opposite of MWI? >>>>>>>>>>> >>>>>>>>>>> To take MWI as something literal, as opposed to maybe a working >>>>>>>>>>> system to understand QM foundations, is maybe taking things too >>>>>>>>>>> far. >>>>>>>>>>> However, it is a part of some open questions concerning the >>>>>>>>>>> fundamentals of >>>>>>>>>>> QM. If MWI, and more generally postulates of quantum >>>>>>>>>>> interpretations, are connected to the Born rule it makes for some >>>>>>>>>>> interesting things to think about. >>>>>>>>>>> >>>>>>>>>>> LC >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> If you read the link, it's pretty obvious that Carroll believes >>>>>>>>>> the many worlds of the MWI, literally exist. AG >>>>>>>>>> >>>>>>>>> >>>>>>>>> Carroll also believes that IF the universe is infinite, then there >>>>>>>>> must exist exact copies of universes and ourselves. This is >>>>>>>>> frequently >>>>>>>>> claimed by the MWI true believers, but never, AFAICT, proven, or even >>>>>>>>> plausibly argued. >>>>>>>>> >>>>>>>>> >>>>>>>>> The idea comes from Tegmark, and I agree with you, it necessitate >>>>>>>>> more than an infinite universe. It requires also some assumption of >>>>>>>>> homogeneity. >>>>>>>>> >>>>>>>> >>>>>>>> Our universe is, on a large scale, homogeneous. But it can't be >>>>>>>> infinite since it has only been expanding for finite time, 13.8 BY. I >>>>>>>> had a >>>>>>>> discussion with Brent about this some time ago, and he claimed finite >>>>>>>> in >>>>>>>> time doesn't preclude infinite in space. I strongly disagree. Perhaps >>>>>>>> I am >>>>>>>> missing something. Wouldn't be the first time. AG >>>>>>>> >>>>>>> >>>>>>> I think what you may be missing is that in popular (but misleading) >>>>>>> accounts of the BB they often say everything originated from a point, >>>>>>> rather than everywhere at once. To say "everything came from a point" >>>>>>> is >>>>>>> at best only valid for describing the observable universe (or any >>>>>>> finite >>>>>>> portion of the universe) but is invalid to extrapolate it to the whole >>>>>>> universe, which may be spatially infinite. >>>>>>> >>>>>> >>>>>> I am not assuming our universe began from a mathematical point, but I >>>>>> do assume that 13.8 BYA it was very very small, the observable and >>>>>> unobservable parts. >>>>>> >>>>> >>>>> Why do you assume this? Most cosmologists make no such assumption. >>>>> Under the concordance (standard assumed) model of cosmology, space is >>>>> infinite. >>>>> >>>>> >>>>>> >>>>>> >>>>>> >>>>>> I don't think there is an implied disconnect between our >>>>>> measurements of the CMBR and what an observer would measure in parts we >>>>>> have no access to. It was everywhere hot and dense, and very very small. >>>>>> >>>>> >>>>> There's no observational motivation for the universe being very very >>>>> small at the beginning. It could have been small, large or infinite, for >>>>> all we know. >>>>> >>>> >>>> I've never read a description of inflation where the universe is >>>> described as very large spatially when it initiates. Never. It's always >>>> claimed it begins a few Planck durations (10^-43 seconds) after the BB, at >>>> which time the spatial diameter is many orders of magnitudes smaller than >>>> the diameter of a proton. It then expands to the diameter of the Earth or >>>> the Solar System before terminating, all this occuring within the first >>>> second after the BB. AG >>>> >>> >>> I think we need to clearly distinguish between three periods, which are >>> frequently confused: >>> >>> 1. "quantum vacuum phase" Size: ??? Time: ??? >>> If inflation began as a fluctuation in the vacuum, the vacuum was a >>> pre-existing initial condition. We can say nothing of it's size or how long >>> it has existed. Alternatively, this vacuum may have already been in a >>> state of exponential expansion and required no fluctuation to get started. >>> >>> >>> 2. "Inflation start" Size: (min = Planck size, max = ???) Time: (min = >>> fraction of second before hot stage of BB, max = finite but otherwise >>> unlimited time ago). >>> If inflation started as a fluctuation it could have started very small, >>> but it would then grow exponentially forever. How big it was when it >>> stopped for us we can't say, but we can guess it had to have gone on for at >>> least 10^-32 seconds to fit with observations. This is only the minimum >>> time, there's no known upper bound. There's not necessarily any cooling >>> during this time as the heat doesn't enter the picture until inflation >>> begins to stop somewhere. >>> >>> 3. "Local inflation end", Size of inflating space: (undefined but ever >>> growing), Size of pocket from outside: (finite but growing), Apparent size >>> of pocket from inside: (finite or infinite depending on shape of the >>> universe), Time: 13.8 BY ago. >>> >>> The "T = 0 of the BB" no longer makes sense in the inflation picture, >>> the only place we can begin to speak of absolutes with time is when we >>> speak of the local end to inflation in our pocket. >>> >>> Jason >>> >> >> I'll say it again. One the main reasons to posit inflation is to explain >> the observable large scale homogeneity of a universe that is now NOT >> causally connected. If the universe was very very tiny when inflation >> started, it WAS then causally connected, >> > > The *observable* part of the universe is posited to have once been > causally connected to come to thermal equilibrium but not necessarily the > entire universe. >
OK, but based on our best measurements, we live in a closed, accelerating and expanding hypersphere, since the curvature is NOT zero and NOT negative. I prefer to go with what we think we know, rather than with a model which is completely speculative. AG > > >> and inflation preserved the homogeneity. This is what Guth was trying to >> solve with inflation, among other problems, such as no detectable >> monopoles. This entire logic breaks down if one assumes an infinite >> universe at the time of inflation. >> > > Correct, using inflation and previous causal connectedness does not > produce for homogeneity of temperature to all parts of the universe if the > universe is infinite. > So far, as I just stated, our best evidence does NOT suggest an infinite universe. AG > At best it can only extend to some finite region of that universe. But > once you are working in an inflationary model, you already have accepted > there is a large scale where the universe is not homogenous (pocket regions > vs. the rapidly inflating regions of vacuum). > I don't see why assuming inflation implies acceptance of large parts of the UNobservable universe which is NOT homogeneous. AG > > >> In this case, the infinite universe was always homogeneous even though it >> was never causally connected. >> > > That is another possibility that avoids inflation as an explanation of > homogeneity: To simply assume everything at all places began at the same > temperature and density. > If so, why did Guth think homogeneity needed an explanation? On its face, thermal equilibrium for a non causally connected universe seems improbable. AG > > >> Further, how could it have been so hot 380,000 years after the BB if it >> wasn't dense at that time? >> > > Actually the universe was not very dense at the time of 380,000 years. It > was billions of times more sparse than Earth's atmosphere. Each time the > scale > factor <https://en.wikipedia.org/wiki/Scale_factor_(cosmology)> halves > going backwards in time, the temperature doubles, and the density increases > by a factor of 8 (2 cubed). You can follows this backwards at least until > the temperature is about 10^27 K, far far hotter and denser than 380,000 > years, back to a time just a fraction of a second after inflation ended. > Yes, it was far hotter and denser just after the BB, than at 380,000 years. But contrary to what you allege above and below, it must have far hotter and denser at 380,000 years, than it is today, 2.7 deg K, so hot and dense that it was opaque to light. I am just saying that it does seem to be cooling as it expands, and the curvature data seems to imply smallness just after the BB. Moreover, applying the Cosmological principle, it couldn't have been homogeneous on large scale in the finite observable region, and at the same time infinite and non-homogeneous in regions we can't observe. AG > > >> An infinite universe right after the BB would be COOL, >> > > Right after inflation predicts it could have been as high as 10^27 degrees. > Our observations agree with our theory which predicts at about 1 second it > was 10s of billions of degrees, falling to 10s of millions of degrees after > 20 minutes. > At 380,000 years the temperature was about 3000 degrees. > At 13.8 billion years it is about 2.7 degrees. > > From: http://kias.dyndns.org/astrophys/cosmology.html > eventtemperature (K)scale factornow / scale factorthentime > strong forces freeze out 1027 3.7 * 1026 10-35 s > weak forces freeze out 1015 3.7 * 1014 10-10 s > protons, neutrons freeze out 1013 3.7 * 1012 0.0001 s > neutrinos <http://kias.dyndns.org/astrophys/particles.html> decouple 3 * > 1010 1.1 * 1010 1 s > electrons freeze out 6 * 109 2.2 * 109 100 s > primordial 2H, 4He form 9 * 108 3.3 * 108 2-15 minutes > > eventtemperature (K)scale factornow / scale factorthentime > photons decouple, atoms form 3000 1091 377000 years > first stars 60 10.4 109 years > today 2.73 1 1.378 * 1010 years > > and COOLER after 380,000 years had elapsed. All of the foregoing makes a >> decent case for a universe which was very very tiny right after the BB. AG >> > > I still see no connection between the temperature at time 380,000 years, > and the size of the universe. Can you do more to explain more why you > think there is a relation? I can see how you might relate the initial > temperature and density at an earlier time to the temperature and density > after 380,000 years, but I am not seeing how you relate the size of the > universe to either the temperature or density at time 380,000 years. > > 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/666ba0a0-918d-422f-b2ed-f0ded39b82b1%40googlegroups.com.
