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 <
>>> [email protected]> 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 <
>>>>> [email protected]> 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 <[email protected]>
>>>>>>> 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
>
>>
>>>
>>> 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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