Re: [Phys-l] The Cosmological Constant from Ricci Dark Energy

[Spinozalens@aol.com]

In a message dated 11/15/2009 7:44:47 PM Eastern Standard Time,  
betwys1@sbcglobal.net writes:

Spinozalens@aol.com wrote:
> We see that the Hubble radius is  expanding into the De Sitter Horizon 
and  
> that under these  simple assumptions the end state for any Hubble volume 
is  
> a  timeless De Sitter Universe. Of course whether such a state is stable 
or  
> not  is an open question. This prediction has several problems  including 
the  issue  of Boltzmann brains. 
>  
>  Bob Zannelli 
>   
I think at this stage, the issue  of  the Boltzmann brains is probably 
settled.
But branes - that's  another matter!   :-)

Brian W





Brian this issue of Boltzmann brains relates to the problem of an eternal  
De Sitter space. An interesting but speculative model has been proposed by  
Sean Carroll and his grad student Chen which postulate that regions  of De 
Sitter space can tunnel into new Universes making this whole  scenario quite 
attractive philosophically, though of course that is no  scientific 
criteria. Some theorists think the whole a De Sitter space  volume will decay into 
something else altogether. See below
 
Bob Zannelli 
 
 
 
 
_More  Boltzman Brain Problems_ 
(http://theeternaluniverse.blogspot.com/2009/07/more-boltzman-brain-problems.html)  

 
I was looking for new theoretical cosmology papers on arxiv.org today and 
saw  there were a few on issues relating to Boltzmann Brains.

Basically here's  the problem: 
    1.  There are, and always will be, only finitely many energy sources 
necessary  to support the kind of intelligent life that progresses up through 
a long  evolutionary path. (These sources are basically stars.)  
    2.  This means the number of such "real observers" has to be finite 
regardless  of the age of the universe.
    3.  De-Sitter space has thermal fluctuations that create a very small 
but  non-zero probability that intelligent life will spring from the vacuum 
long  enough to make an observation.  
    4.  Given our De-Sitter space seems it will expand forever, the number 
or  Boltzmann brains will dwarf the number of "real observers" like 
irrationals  dwarf rational numbers. (Let's leave countablity out of this, just 
needed some  sort of analogy. Also, "real observers" are finite, unlike rational 
numbers.)  
    5.  Firstly, this is weird to think there should be more Bolzmann 
Brains that  normal observers.  
    6.  Second, it is highly improbable if you are intelligent life that 
you are  not a Bolzman brain, so given the life on our planet seems to be 
"real  observers" we are a huge anomaly. Again weird.
Now, scientists don't  like the above so some try to find ways of getting 
rid of Bolzman Brains. The  papers today discussed things like the universe 
having a half life of 20 billion  years with the de-Sitter space decaying. 
Then there is a cutoff where there  isn't enough time for Bolzmann Brains to 
pop into existence.

Now, I don't  do this kind of research since it is too crazy. But someone 
like me always gets  a kick out of reading such papers. It's like science 
junk food that actually in  some cases passes peer review. (However, in their 
defense, Bolzman Brains may  someday be a technical hiccup that leads to 
important new physics.)
 
_http://theeternaluniverse.blogspot.com/2009/07/more-boltzman-brain-problems
.html_ 
(http://theeternaluniverse.blogspot.com/2009/07/more-boltzman-brain-problems.html)