On Tuesday, June 29, 2021 at 5:24:06 PM UTC-5 Bruce wrote:
> On Wed, Jun 30, 2021 at 4:50 AM Lawrence Crowell <[email protected]>
> wrote:
>
>> The argument is a bit difficult, but the dS vacuum has positive energy
>> and there is some probability of it tunneling to a lower value.
>
>
> In order for this to be possible, there must be some "landscape" of
> possible values for the vacuum energy. There is no evidence for any such
> thing. The data are best described by a cosmological constant -- that is, a
> fixed constant function. In order for there to be some "landscape", or some
> lower possible value for the vacuum energy, there must be some function
> that describes this. That would require a dynamical origin for vacuum
> energy, and be the opposite of a simple constant.
>
> Any theory that goes in this direction is necessarily unevidenced
> speculation, no matter how arcane the mathematics might be.
>
It is tied to inflationary cosmology, which has some empirical support. It
does give predictions on the CMB and ΛCDM, which has a fair amount of
empirical support. The B-modes for gravitational waves induced by inflation
seemed a good bet back in 2015, but the problem is that polarization from
galactic dust leaves a similar signature. So the data fell from 6-sigma to
3-sigma. The situation though is improving. It is turning into a very
difficult signal processing issue.
Inflationary cosmology implies the sort of multi-cosmogony or multiverse (I
never liked that term) model. If B-modes are found this will gives some
support for that. In that case we will have some data to support work on
different vacua for cosmogonies. Where things go from there is uncertain. I
tend to think that alternate cosmologies with Λ >> Λ_obs may in fact be a
form of off-shell condition. These may then not in fact be real worlds as
such. I also think this might be a way to do radiative corrections in
general, not just cosmology, that avoids a lot of redundancies in Feynman
diagram approaches and that further avoids confusions over virtual states.
>
> It may do this "drip by drip" with Gibbon-Hawking radiation.
>
>
>
> I think Gibbon-Hawking radiation is rather like Unruh radiation. -- a test
> body in the expanding universe will experience radiation, but the vacuum
> energy does not decay, since the whole of spacetime is not filled with such
> radiation -- it is only in the presence of a test body that it is
> observable. Just like with Unruh radiation. The spacetime surrounding the
> accelerating body is not filled with radiation since the inertial observer
> does not see radiation. All he sees is the accelerated body emitting the
> occasional thermal particle.
>
> Bruce
>
It is similar to Unruh radiation in that the cosmological horizon is a
particle horizon. It is though also similar to Hawking radiation, and an
inertial observer in principle can observe it. The practical problem of
course is the quanta emitted have wavelength that is comparable to the
horizon distance L = √(3/Λ). If one wants hold to the analogue with Unruh
radiation then the cosmological constant does induce an accelerated frame
dragging of particles.
I ponder whether in this multiple cosmogony perspective that all other
vacua have transition amplitudes to the lowest energy vacuum. These other
vacua the correspond to what we might call virtual cosmogonies or off-shell
states. The vacuum we are in would then be the lowest with the Λ_obs the
physical vacuum that has a fundamental mass-gap with zero energy or T^{00}
= 0. The internal emission of Gibbon-Hawking radiation might be the only
way the vacuum can transition to zero. If so there would be a restriction
on the number of physical cosmogonies, maybe down to just the one we
observe.
LC
>
> It could also transition into an anti-de Sitter vacuum. In that case the
>> vacuum energy is negative, but there are conditions for regular eigenvalued
>> orbits that define a minimum. That is a difficult subject involving the
>> moduli of hyperbolic geometries. So string theory is not needed to
>> understand this. In fact the de Sitter vacuum is "anti-string," and string
>> theory has nothing directly to do with the spectra of elementary particles
>> or the vacuum in the observable universe, That is except with colliding
>> black holes.
>>
>> LC
>>
>> On Monday, June 28, 2021 at 5:31:47 PM UTC-5 Bruce wrote:
>>
>>>
>>> Do you have any actual evidence that the deSitter vacuum is unstable? Or
>>> is this just a speculative idea based on the idea of a string theory
>>> landscape?
>>>
>>> Bruce
>>>
>>
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