On Thu, Oct 3, 2019 at 10:14 AM Lawrence Crowell <
goldenfieldquaterni...@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.
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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