• Als Spam markieren
• Beitrag melden

• 
  Diese Gruppe Alles

• Archiv
• RSS-Feeds

• Kontakt
• Hilfe
• Impressum
• Datenschutz

Physicists Calculate Number of Universes in the Multiverse: 10^10^16.

Physicists Calculate Number of Universes in the Multiverse: 10^10^16.

Thursday, October 15, 2009
Physicists Calculate Number of Universes in the Multiverse
If we live in a multiverse, it's reasonable to ask how many other
distinguishable universes we may share it with. Now physicists have an
answer.

One of the curious developments in cosmology in recent years has been
the emergence of the multiverse as a mainstream idea. Instead of the Big
Bang producing a single uniform universe, the latest thinking is that it
produced many different universes that appear locally uniform.

One question that then arises is how many universes are there. That may
sound like the sort of quantity that is inherently unknowable but Andrei
Linde and Vitaly Vanchurin at Stanford University in California have
worked out an answer, of sorts.

Their answer goes like this. The Big Bang was essentially a quantum
process which generated quantum fluctuations in the state of the early
universe. The universe then underwent a period of rapid growth called
inflation during which these perturbations were "frozen", creating
different initial classical conditions in different parts of the cosmos.
Since each of these regions would have a different set of laws of low
energy physics, they can be thought of as different universes.

What Linde and Vanchurin have done is estimate how many different
universes could have appeared as a result of this effect. Their answer
is that this number must be proportional to the effect that caused the
perturbations in the first place, a process called slow roll inflation,
and in particular to the number "e-foldings" of slow roll inflation.

Of course, the actual number depends critically on how you define the
difference between universes.

Linde and Vanchurin have applied some reasonable rules to calculate that
the number of universes in the multiverse and have totted it up to at
least 10^10^10^7. A "humungous" number is how they describe it, with no
little understatement.

How many of these could we actually see? What's interesting here is that
the properties of the observer become an important factor because of a
limit to the amount of information that can be contained within any
given volume of space, a number known as the Bekenstein limit, and by
the limits of the human brain.

Linde and Vanchurin say that total amount of information that can be
absorbed by one individual during a lifetime is about 10^16 bits. So a
typical human brain can have 10^10^16 configurations and so could never
disintguish more than that number of different universes.

10^10^16 is a big number but it is dwarfed by the "humungous" 10^10^10^7.

"We have found that the strongest limit on the number of different
locally distinguishable geometries is determined mostly by our abilities
to distinguish between different universes and to remember our results,"
say Linde and Vanchurin

So the limit does not depend on the properties of the multiverse but on
the properties of the observer.

How profound is that!

Ref: arxiv.org/abs/0910.1589: How Many Universes Are In The Multiverse?


************************************************************************

http://arxiv.org/abs/0910.1589

How many universes are in the multiverse?

Andrei Linde, Vitaly Vanchurin
(Submitted on 9 Oct 2009)
We argue that the total number of distinguishable locally Friedmann
"universes" generated by eternal inflation is proportional to the
exponent of the entropy of inflationary perturbations and is limited by
$e^{e^{3 N}}$, where $N$ is the number of e-folds of slow-roll
post-eternal inflation. For simplest models of chaotic inflation, $N$ is
approximately equal to de Sitter entropy at the end of eternal
inflation; it can be exponentially large. However, not all of these
universes can be observed by a local observer. We show that in the
presence of a cosmological constant $\Lambda$ an observable entropy of
the cosmological perturbations, as well as the entropy of usual matter,
is bounded by $|\Lambda|^{-3/4}$. In the context of the string theory
landscape, the overall number of different universes is expected to be
exponentially greater than the total number of vacua in the landscape.
We discuss the possibility that the strongest constraint on the number
of distinguishable universes may be related not to the properties of the
multiverse but to the properties of observers.






--
Bert ( A W RvB )
bert@rjrsnvbrn.nl
www.rjrsnvbrn.nl

Antworten