On Thursday, October 3, 2019 at 5:52:08 PM UTC-5, Alan Grayson wrote:
>
>
>
> On Thursday, October 3, 2019 at 4:22:20 PM UTC-6, Lawrence Crowell wrote:
>>
>> On Thursday, October 3, 2019 at 7:59:51 AM UTC-5, Alan Grayson wrote:
>>>
>>>
>>>
>>> On Thursday, October 3, 2019 at 3:45:41 AM UTC-6, Lawrence Crowell wrote:
>>>>
>>>> On Wednesday, October 2, 2019 at 7:31:56 PM UTC-5, Bruce wrote:
>>>>>
>>>>> On Thu, Oct 3, 2019 at 10:14 AM Lawrence Crowell <
>>>>> goldenfield...@gmail.com> wrote:
>>>>>
>>>>>> On Wednesday, October 2, 2019 at 6:41:32 PM UTC-5, Bruce wrote:
>>>>>>>
>>>>>>> On Thu, Oct 3, 2019 at 9:21 AM Lawrence Crowell <
>>>>>>> goldenfield...@gmail.com> wrote:
>>>>>>>
>>>>>>>> On Wednesday, October 2, 2019 at 5:46:50 PM UTC-5, Bruce wrote:
>>>>>>>>>
>>>>>>>>> On Thu, Oct 3, 2019 at 3:03 AM Alan Grayson <agrays...@gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> In this case I was just responding to Bruce's certainty that
>>>>>>>>>> inflation is mostly a red herring. I highly respect his opinions,
>>>>>>>>>> but in
>>>>>>>>>> this case, based on my study of this particular issue, I disagree. I
>>>>>>>>>> am
>>>>>>>>>> open to being proved wrong, but insults don't cut it. At least you
>>>>>>>>>> agree
>>>>>>>>>> that inflation does explain homogeneity. Aren't you curious about
>>>>>>>>>> Bruce's
>>>>>>>>>> take on this particular issue? AG
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Inflation can result in an increase in flatness and homogeneity.
>>>>>>>>> But that is relevant only if flatness and homogeneity were problems
>>>>>>>>> in need
>>>>>>>>> of explanation.
>>>>>>>>>
>>>>>>>>> Bruce
>>>>>>>>>
>>>>>>>>
>>>>>>>> The real problem is how did disparate regions of the universe
>>>>>>>> become uniform when there would have been no causal connection between
>>>>>>>> them. In particular with homogeneity inflation provides a mechanism
>>>>>>>> whereby
>>>>>>>> deviations from homogeneity and isotropy are uniform.
>>>>>>>>
>>>>>>>
>>>>>>> Fine. Provided they were not uniform at the start. It is all a
>>>>>>> matter of distributions and in initial conditions. And you know nothing
>>>>>>> about either, so why solve a problem before you know it exists?
>>>>>>> Besides,
>>>>>>> can you achieve thermal equilibrium in a non-equilibrium state in
>>>>>>> 10^{-35}
>>>>>>> sec?
>>>>>>>
>>>>>>> Bruce
>>>>>>>
>>>>>>
>>>>>> Inflation started on a fiducial at 10^{-36}sec and lasted until
>>>>>> 10^{-32} sec. Since the particle fields were near the Planck scale in
>>>>>> energy this inflationary cycle lasted some 10^{10} times the
>>>>>> periodicities
>>>>>> of fields. That is enough to approximately have thermal equilibrium.
>>>>>>
>>>>>
>>>>> The problem is not the periodicity of the fields. The problem is the
>>>>> uniformity of the initial conditions. As Sabine points out, inflation
>>>>> just
>>>>> replaces one set of unknown initial conditions with another.
>>>>>
>>>>> I would also take issue with her suggestion that inflation solves some
>>>>> problems with the origin of the fluctuations seen in the CMB. Inflation
>>>>> might provide a framework, but it does not provide an explanation for
>>>>> these
>>>>> fluctuations. The fluctuations are built in by hand, and the gaussian
>>>>> nature of the fluctuations is also built in by hand. So these features of
>>>>> the CMB are not "explained" by inflation in any sense at all. There
>>>>> gaussian nature, and the relative magnitude of 10^{-5} are both free
>>>>> parameters that are set by hand.
>>>>>
>>>>>
>>>> The initial conditions, what ever they were, were flattened out though
>>>> by inflation. The anisotropy in the CMB is due to details in the field
>>>> configuration of the scalar field. The theory just provides the action S =
>>>> ∫d^4x√g(φR + L(φ)), but not the explicit initial conditions or the
>>>> configuration of the field at reheating. The point though is these details
>>>> were exponentially attenuated by inflation so their magnitude is small.
>>>> Estimates of this works out pretty well.
>>>>
>>>> LC
>>>>
>>>
>>> I have a different model. Inflation didn't attentuate the initial
>>> condition. Rather it *preserved* an initial condition of virtually
>>> perfect uniformity, which was about the one part in 100,000 observed in the
>>> CMBR. Before inflation began, the universe was tiny, say much less than the
>>> diameter of a proton. It was so small in comparison to the SoL, that it was
>>> in thermo equilbrium *before* inflation began. The sudden huge
>>> expansion preserved the already existing thermo equilibrium. If inflation
>>> didn't happen, the time of recombination would have occurred much later
>>> than 380,000 years after the BB, and by that time the original very tiny
>>> fluctuations would have increased, resulting in relatively large variations
>>> in the CMBR, much more than one part in 100,000. What I haven't calculated
>>> -- because I don't know how -- is whether the time duration before
>>> inflation was long enough, despite the large SoL, for the universe to reach
>>> an approximate thermo equilbrium of one part in 100,000. AG
>>>
>>
>> For various reasons this will not work. With inflation the cosmological
>> horizon was 10^{-27}m in radius. The real problem is that without inflation
>> winding back the cosmic time leads to nonsensical conditions.
>>
>> LC
>>
>
> Why won't it work? What are the nonsensical conditions when the clock is
> reversed? I didn't claim there is no inflation, so what have the
> nonsensical conditions have to do with anything I wrote? AG
>
In order to explain it fully would require pumping out a fair amount of
general relativity stuff. I am not going there right now --- too tired. If
what you say were to work it would have already been proposed and accepted.
LC
>
>>
>>>
>>>>
>>>>>
>>>>> Winding the timeline of the universe back in time based on no
>>>>>> inflation results in a problem because of high z physics, in particular
>>>>>> the
>>>>>> CMB. Without this high vacuum energy and extreme acceleration there is
>>>>>> no
>>>>>> way to get everything in the same region so they causally evolved
>>>>>> according
>>>>>> to the same set of initial conditions. In fact before inflation this was
>>>>>> a
>>>>>> problem that buggered cosmologies back in the 1960s and 70s.
>>>>>>
>>>>>
>>>>> Perhaps it took a while to realise the importance of initial
>>>>> conditions......
>>>>>
>>>>> Bruce
>>>>>
>>>>>
>>>>
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