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From: Russell Standish <r.standish.domain.name.hidden>

Date: Fri, 28 Jul 2006 00:07:37 +1000

Thanks for giving a digested explanation of the argument. This paper

was discussed briefly on A-Void a few weeks ago, but I must admit to

not following the argument too well, nor RTFA.

My comment on the observer moment issue, is that in a Multiverse, the

measure of older observer moments is less that younger ones. After a

certain point in time, the measure probably decreases exponentially or

faster, so there will be a mean observer moment age.

So contra all these old OMs dominating the calculation, and giving

rise to an expected value of Lambda close to zero, we should expect

only a finite contribution, leading to an expected finite value of

Lambda.

We don't know what the mean age for an observer moment should be, but

presumably one could argue anthropically that is around 10^{10}

years. What does this give for an expected value of Lambda?

Of course their argument does sound plausible for a single universe -

is this observational evidence in favour of a Multiverse?

Cheers

On Thu, Jul 27, 2006 at 11:08:04AM -0700, "Hal Finney" wrote:

*> This is actually a very interesting paper, by Starkman and Trotta. I had
*

*> seen some mention of it but hadn't tracked it down. Here is the abstract:
*

*>
*

*> The paper basically shows that observers (or civilizations) can last
*

*> longer in universes with smaller CC's. The CC eventually puts an end
*

*> to the observations that can be made, because the expansion gets too
*

*> fast and there is no longer enough energy density. The higher the CC,
*

*> the sooner this happens. With CC's as high as what we observe, the
*

*> theoretical lifetime of civilization is much shorter than in universes
*

*> with smaller CC's.
*

*>
*

*> The authors choose to use as their measure, the number of times the
*

*> CC can be measured in a given universe. This makes low-CC universes
*

*> have a much higher measure, because the window for CC observations is
*

*> longer in those. Hence they conclude that the highest probability is
*

*> for a CC much smaller than we observe, and so our own CC value cannot
*

*> be explained anthropically.
*

*>
*

Date: Fri, 28 Jul 2006 00:07:37 +1000

Thanks for giving a digested explanation of the argument. This paper

was discussed briefly on A-Void a few weeks ago, but I must admit to

not following the argument too well, nor RTFA.

My comment on the observer moment issue, is that in a Multiverse, the

measure of older observer moments is less that younger ones. After a

certain point in time, the measure probably decreases exponentially or

faster, so there will be a mean observer moment age.

So contra all these old OMs dominating the calculation, and giving

rise to an expected value of Lambda close to zero, we should expect

only a finite contribution, leading to an expected finite value of

Lambda.

We don't know what the mean age for an observer moment should be, but

presumably one could argue anthropically that is around 10^{10}

years. What does this give for an expected value of Lambda?

Of course their argument does sound plausible for a single universe -

is this observational evidence in favour of a Multiverse?

Cheers

On Thu, Jul 27, 2006 at 11:08:04AM -0700, "Hal Finney" wrote:

-- *PS: A number of people ask me about the attachment to my email, which is of type "application/pgp-signature". Don't worry, it is not a virus. It is an electronic signature, that may be used to verify this email came from me if you have PGP or GPG installed. Otherwise, you may safely ignore this attachment. ---------------------------------------------------------------------------- A/Prof Russell Standish Phone 8308 3119 (mobile) Mathematics 0425 253119 (") UNSW SYDNEY 2052 R.Standish.domain.name.hidden Australia http://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 ---------------------------------------------------------------------------- --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list.domain.name.hidden To unsubscribe from this group, send email to everything-list-unsubscribe.domain.name.hidden For more options, visit this group at http://groups.google.com/group/everything-list -~----------~----~----~----~------~----~------~--~---Received on Thu Jul 27 2006 - 21:00:00 PDT

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