Yes, I agree. But it could be that information loss is a bit ambiguous. E.g.
't Hooft has shown that you can start with a deterministic model exhibiting
information loss and end up with quantum mechanics.


----- Original Message ----- 
From: "Jesse Mazer" <[EMAIL PROTECTED]>
To: <>
Sent: Monday, April 10, 2006 03:22 AM
Subject: Re: why can't we erase information?

> Saibal Mitra wrote:
> >
> >
> >How would an observer know he is living in a universe in which
> >is lost? Information loss means that time evolution can map two different
> >initial states to the same final state. The observer in the final state
> >thus
> >cannot know that information really has been lost.
> If he is able to figure out the fundamental laws of physics of his
> then he could see whether or not they have this property of it being
> possible to deduce past states from present ones (I think the name for
> property might be 'reversible', although I can't remember the difference
> between 'reversible' and 'invertible' laws). For example, the rules of
> Conway's "Game of Life" cellular automaton are not reversible, but if it
> were possible for such a world to support intelligent beings I don't see
> it wouldn't be in principle possible for them to deduce the underlying
> rules.
> As for the question of why we live in a universe that apparently has this
> property, I don't think there's an anthropic explanation for it, I'd see
> as part of the larger question of why we live in a universe whose
> fundamental laws seem to be so elegant and posess so many symmetries, one
> which is time-symmetry (or to be more accurate, CPT-symmetry, which means
> the laws of physics are unchanged if you switch particles with
> and flip the 'parity' along with reversing which direction of time is
> labeled 'the future' and which is labeled 'the past'). Some TOEs that have
> been bandied about here say that we should expect to live in a universe
> whose laws are very compressible, so maybe this would be one possible way
> answering the question.
> Jesse
> >

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