so you'd need some fundamentally different theory, unlike the ones physicists know, for
that to be true. Such a thing is certainly logically possible, but you can't really
point to the time symmetry of existing theories as evidence that it's the "easiest" of
ways to explain away Bell's results.
A photon has a very limited memory and doesn't partake in thermodynamics on
its own.
I don't know what you mean by "memory", or how thermodynamics is relevant. Technically
you should be able to apply thermodynamics to any system which can have multiple states,
including a single particle in a box, just by making some choice about how to
coarse-grain all the "microstates" into a set of "macrostates".
The onus is to show why it wouldn't be influenced equally by past and future
boundary conditions if time is fundamentally symmetric
You can say it's influenced equally, in the sense that complete knowledge of either one
can be used to determine the quantum state of a system. But again, that's fundamentally
different from saying neither set of boundary conditions alone is sufficient, that you
need to take into account both at once.
Jesse
On 5 February 2014 09:54, Jesse Mazer <[email protected]
<mailto:[email protected]>> wrote:
On Tue, Feb 4, 2014 at 3:35 PM, LizR <[email protected]
<mailto:[email protected]>> wrote:
On 4 February 2014 23:25, Bruno Marchal <[email protected]
<mailto:[email protected]>> wrote:
On 04 Feb 2014, at 00:29, LizR wrote:
On 4 February 2014 12:23, Jesse Mazer <[email protected]
<mailto:[email protected]>> wrote:
On Mon, Feb 3, 2014 at 5:48 PM, <[email protected]
<mailto:[email protected]>> wrote:
But more generically speaking, would this inference for
blocktime sit at the edge of relativity or at its core.
What I
mean is, beyond that it is an implication of
relativity, have
there been or are there any prospects for developing
blocktime
as it arises from relativity to such point, predictions
get
made? Or any other kind of reinforcement? Or does
blocktime go
on to imply something beyond blocktime?
If "block time" is taken as a definite ontological
statement about
all times "existing" in exactly the same sense, rather than
just
referring to the idea of treating time as a dimension
conceptually
or in our mathematical models, then I think it's a
metaphysical
postulate that goes beyond anything directly implied by
relativity.
Relativity says that all frames, with their different
definitions
of simultaneity, are on equal footing as far as the laws of
physics
are concerned, but it doesn't deal with ontology. If someone
proposes that one frame's definition of simultaneity is
"metaphysically preferred" in the sense it defines the "true
present", but adds the caveat that this frame is not in any
way
physically preferred so that no conceivable experiment could
determine which frame it is, this wouldn't contradict the
physics.
It would be an "interpretation" of SR, similar to the
different
"interpretations" of QM which postulate different things
about
ontology (the real existence of other worlds in the MWI, or
a
single world with hidden variables in Bohmian mechanics, for
example) but are indistinguishable experimentally.
SR directly demonstrates block time via the relativity of
simultaneity.
This can be tested experimentally.
That said, if you subscribe to any form of Occam's razor or
even a
criteria of "elegance" when it comes to choosing between
different
metaphysical hypotheses, it seems a lot simpler to assume
that
there is no metaphysically preferred definition of
simultaneity,
just as I think many would agree the MWI is the simplest
way of
interpreting the physical theory of QM. Adding extra "purely
metaphysical" entities to a theory, which don't correspond
to
anything that appears in the mathematical formalism of the
theory
itself (which would apply to things like a "true present"
or to
hidden variables in QM), seems a bit like postulating that
there
are invisible intangible elves sitting on each person's
head which
have no causal effects on anything we can measure; sure it's
logically possible, but it seems like a very inelegant and
arbitrary way for reality to work.
The MWI is deterministic, however, and hence has hidden
variables.
But not "hidden variable" in the EPR sense. In the MWI, there
are hidden
universes, they are not variable, but terms in the universal
wave, and
we just don't know which terms apply to us. If it was hidden
variable in
the EPR sense, then by Bell, they would be non-local, and you
would
conclude falsely (like Clark) that the MWI has to be non local
(which I
doubt very much).
No, as I explained elsewhere, Bell's inequality rests on 4
assumptions, and
the easiest assumption to remove is that time is asmmetric at the
fundamental level (which /in any case/ physics indicates it isn't,
except
for neutral kaon decay - which I dount has ever been used in an EPR
experiment).
As I've said to you in the post at
http://www.mail-archive.com/[email protected]/msg46130.html , the
type of time-symmetry seen in modern physics--which just says that the
same laws
can be used to retrodict past states as are used to predict future
states, but
doesn't say you *need* information about the future as well as the past
to
predict the state in a given region of spacetime--is not enough to
evade the
conclusions of Bell's theorem. In order to do that you'd need either a
theory
where determining the state of a region does require knowing both its
past and
its future, or you'd need some strong restrictions on the possible
boundary
conditions, both of which would be pretty exotic assumptions, not ones
I'd
consider to be the "easiest" modification of Bell's assumptions. In the
case of
the type of dynamical time-symmetric (or CPT-symmetric) theories that
physicists
have found useful in describing nature, where you can use a set of
initial
conditions to predict a later state, the argument about conditioning on
a slice
of the past light cone I mentioned at
http://www.mail-archive.com/[email protected]/msg45832.html (and
which matches Bell's discussion of conditioning on slices of past light
cones in
his "La nouvelle cuisine" paper) still works fine to show that if the
theory is
local realistic (and doesn't include parallel universes), Bell
inequalities
should not be possible to violate.
Jesse
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