On 29 Nov 2017, at 17:21, [email protected] wrote:
On Wednesday, November 29, 2017 at 3:24:38 PM UTC, Bruno Marchal
wrote:
On 29 Nov 2017, at 04:59, Bruce Kellett wrote:
On 29/11/2017 2:29 pm, John Clark wrote:
On Tue, Nov 28, 2017 at 9:05 PM, Brent Meeker <[email protected]>
wrote:
>> And how is the Eternal Inflation Multiverse fundamentally
different from the String Theory
Multiverse?
> I didn't say they were different from each other; I said
they were different from the mulitple worlds of Everett which all
share the same physics with the same physical constant values.
I see no reason all the Everett worlds have the same physics,
Everettian worlds follow from assuming that the Schrödinger equation
applies everywhere without exception, so that all physical evolution
is unitary. A change in the underlying physics -- such as a change
in the value of fundamental constants, Planck's constant or
Newton's constant for example -- would not be unitary, so cannot
occur in MWI.
The same reasoning applies to the Level I multiverse from eternal
inflation -- same physics everywhere. However, the level ii
multiverse from the string theory landscape has physical constants
and the number of space-time dimensions varying from world to world.
Yes. The Everettian view of string theory leads to a multi-
multiverse. Perhaps 10^500 multiverses ...
Wow! What a coincidence! Same estimate as the landscape in string
theory. Is this before or after Joe the Plumber did his experiments
which adds universes according to the MWI? AG
I was using the string theory landscape for saying this. If the
physical reality of the landscape are quantum reality, they are all
multiverse in the Everett-Deutch sense.
With Mechanism, we have 0 "universe", only histories and dreams, which
exists in arithmetic. We need to postulate only 0, s(0), s(s(0)) ...,
together with addition and multiplication.
It is the very idea of "universe" which might be spurious. Primary
matter is a sort of last phlogiston. But you will need to study some
papers to get this right.
Bruno
unless it turns out that only one sort of physics can happen. But
lets assume you're right, then the string theory multiverse must be
larger than the many worlds multiverse incorporating everything in
Everett's version and MORE; after all if it contains universes with
radically different laws of physics it must also contain more modest
things like a world where my coin came up heads instead of tails.
I would suggest that there is no such world. Whether a coin comes up
head or tails on a simple toss is not a quantum event; it is
determined by quite classical laws of physics governing initial
conditions, air currents and the like.
It depends. If you shake the coin long enough, the quantum
uncertainties can add up to the point that the toss is a quantum
event. With some student we have evaluate this quantitavely (a long
time ago) and get that if was enough to shake the coin less than a
minute, but more than few seconds ... (Nothing rigorous).
Also, in the Level I multiverse it is quite unlikely that the
initial conditions could differ to an extent such that everything
was identical in the two worlds up to your coin toss. I think
Tegmark is wrong about this. His argument (as outlined in his book)
assumes that worlds are made up at random out of the available
constituents, so every way of filling space-time units is realized
somewhere. But this is wrong. Worlds are not random objects, they
follow the laws of physics, so given some initial conditions, the
future is determined in a deterministic Everettian MW scenario. It
is not the case that everything logically possible happens -- only
those things that follow from the initial conditions by
deterministic evolution happen. So although all possible initial
conditions may be realized somewhere, not everything can follow
deterministically -- the laws of physics cannot be broken.
OK. We agree on this.
Bruno
Bruce
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