Re: Question for Cosmologists

On 1/13/06, Pim van Meurs <pimvanmeurs@yahoo.com> wrote:
>
> Inflation is what happened in a fraction of time after the big bang. The
> observed long term change in the cosmological constant would affect the
> acceleration of the universe in time which was smaller in the past than
> in the present (assuming that the results hold). As I have pointed out
> the error bars are sufficiently large.
>
> During the inflationary period, a very large cosmological constant
> stretches cosmological perturbations beyond the Hubble radius.
> http://nedwww.ipac.caltech.edu/level5/Watson/Watson5.html
>
> (^19 Actually, Lambda does not have to be a constant; in-fact, it can be
> a function of time. Such vacuum energies are referred to as
> Quintessence, or Dark energy, and are the subject of much research.)

Thanks. This will be my last post of the day. I checked the references from
above and the dynamic Lambda theories seem to be going in the wrong
direction, i.e. it is decaying.

arxiv:gr-qc/0001051

In this connection we remind the audience that some progress has been
achieved in terms of scalar tensor theories. We believe that these theories
are promising because they might have important aspects shared by attempts
toward unified theories, and also because they provide the simplest
derivation of an exponential potential of the scalar field, allowing us to
implement the "scenario of a decaying cosmological constant" [10]. According
to this scenario, we find lambda not to be a true constant, but to decay
like lambda(t) ∼ t^−2. In the (reduced) Planckian unit system of c = ¯h = 8πG
= M−2 P = 1, the present age of the universe, t0 ∼ 10^10y is about 10^60,
hence giving Lambda(t0) ∼ 10−120; today's cosmological constant is small
only because our universe is old, not because of an unnatural fine-tuning of
the parameters to the accuracy of 120 orders of magnitude.
Received on Fri Jan 13 14:27:56 2006