Re: Two EPR questions

rof_at_maths.tcd.ie
Date: 11/05/04 

Date: Fri, 5 Nov 2004 14:20:44 +0000 (UTC)

"Ilja Schmelzer" <Ilja.Schmelzer@FernUni-Hagen.de> writes:

><rof@maths.tcd.ie> schrieb
>> "Ilja Schmelzer" <Ilja.Schmelzer@FernUni-Hagen.de> writes:

>Yep. The construction of the M_n is of this type. But the X_n\M_n,
>the inner part of the moon, is not perceived. Even if I have some
>perception M_moon of the surface of the moon and some vague
>theoretical ideas what may be inside.

Ok; I see what you're saying. Conceptual information, such as
"Iron is the stablest nucleus", is not represented spatially,
and it is most likely ideas like this which guide your thinking
about what is going on inside planets. I don't disagree with this,
but the sense in which I use the X_n is to refer explicitly to the
procedure which we use to construct a "world around us" from
sensation, and which is explicitly spatial.

>> These matters are relevant for physics because the statistics of
>> the E_n either are or are not representable as a Markov process
>> which factorises in a spatial way, and so these considerations
>> must arise whenever one wants to ask whether an observer will
>> see space.

>Sorry, but you cannot derive if observers will "see" space.
>"Seeing" space means developing a certain realistic theory,
>may be implicit (as a hidden prejudice, instinct, created by
>evolution).

Evolution is another can of worms, best left unopened here, as is
the connection between the brain and conscious experience. Animals
see space, but they don't develop ontological theories. It is only
confused humans who see a brick and then imagine that the brick
isn't really there; that it's only a perceived brick, and that
what "really" exists are tiny particles swirling around under the
influence of various force fields. It's only theoretical physicists
who have to face the dilemma of whether to stick the "reality" sticker
onto the wavefunction or the observables, because the urge to stick
it somewhere is so strong.

>> >> In an ontological theory the splitting needs to be deduced,
>> >> rather than postulated.
>>
>> >The ontological theory postulates the structure and the laws of
>> >the X_n. If these have the form of something localized in a space,
>> >space is postulated. What you perceive is another question,
>> >in the E_n we have, for example, nothing three-dimensional.
>> >We see only two 2D movies. So it is completely unclear what
>> >means spatial structure in the E_n.

>> No; the ontological theory can't make any postulates about the X_n,
>> because the X_n exist only in the mind of the observer, who has
>> constructed them.

>That's a confusion of language levels. A believes that there are
>some X_n in reality. This is an ontological theory proposed by A.

A may think it's on ontological theory, but A is confusing himself.
Imagine there is a digital machine, which takes 1's and 0's as
input. You feed in some sequence of 1's and 0's, generated by
some algorithm. The machine proceeds to construct a Markov model
to predict the sequence. It is successful to some degree - most
of the time it correctly predicts the next input. Has it discovered
reality? Is its Markov model an ontological theory?

The situation that we find ourselves in is that we know that
we cannot perfectly predict the results of measurements (in
EPR experiments, knowing the outcome of a spin measurement in
advance would allow signalling faster than light). This means
that our Markov model cannot perfectly predict the future,
even in principle. We're left with a merely statistical prediction,
although we may conjure up fruitless imaginations about what caused
the result of a particular experiment to be this or that.

Specifically, Bohmian mechanics is an attempt to imagine that
the technique which we use to order our perceptions (representing
a single state of affairs as lots of little states of affairs,
each in its own position, in configuration space, for example),
should still apply even in the absence of any sensible data
to represent. That is, it is supposed that whatever is responsible
for this experiment giving this result, it must be represented
as stuff in space, because that's what we're used to perceiving.
Whether or not a particle even exists can depend on the motion of
the observer (cf. the Unruh effect), so it seems strange to put that
sticky reality label onto the particles and their positions in space.

>We have to decide which language level we want to use - the level
>of A, then we talk about X_n as real states, or on a metalevel where
>we talk about A's X_n as constructions of his mind. Of course, on
>this metalevel we have our metatheory about reality with our own
>X'_n. (This consideration was on meta-meta-level)

All of the X_n are mentally constructed. Putting a sticker on
them saying "reality" doesn't change that. The difference between
what's real and what's not is the same as the difference between
imagined pain and real pain - one is present, the other merely
referred to. We may, for the moment, take a particular formulation
of theoretical physics and work out its consequences, for example
the minimally supersymmetric standard model, and say that, within
that model, this or that particle is really there (and not merely
referred to), but declaring that the model is "out there", beyond
the mind of the person who thinks it, governing the evolution
of the world, is like saying that, since 1 typically follows
0 in a certain binary sequence, the rule "01" is out there, guiding
the sequence.

>The game is reverse. The theory is prior. Then, a complicated
>data processing starts which makes the E_n compatible with the
>theory using some M_n. A failure of this process is named
>falsification.

>Theories about the data processing are part of some historical
>sciences.

There's a psychological problem which has led theoretical physics
into a nasty corner. It's the problem of physics students learning
too many theories and doing too many exercises. Once they've grown
up, the only thing they can do is take a set of axioms and see
what follows from them. Now we have a situation where the physicists
need to know "What's the Lagrangian?" before they can get any further.
It's like a McDonald's employee starving to death in an orchard
because he can't find the McOven and the McFries. Theorizing
consists of writing down different Lagrangians and working out
their consequences. "The theory is prior." Compute, compute, compute.

It's usually the case that a species of knowledge has to be
very thoroughly understood and the doctrine has to be very mature
before it admits an axiomatic formulation. The process of
discovering, by careful thought and experimentation, what the
actual properties of the object of study are, is necessary
before one can start thinking of compressing all the relevant
information into some axioms. At the moment, however, physicists
are still doing their homework, starting from axioms and deriving
the consequences. Some of the axioms they think they know (quantum
mechanics, Lagrangians, manifolds), and some they imaginatively
produce on their own, but nobody tries to understand starting from
the facts which are right in front of them. That's not what they
were trained to do.

>> >> You do, but giving up either realism or causality won't affect your
>> >> ability to predict X_{n+1} from X_n, since they are merely rules of
>> >> thumb for generating representations.
>>
>> >No, the rules of thumb are questioned. I have no way to construct
>> >some X_n in the usual (causal, realistic) meaning which has the
>> >property of Lorentz-invariance.
>>
>> Lorentz invariance and relativity are important when one needs to
>> compare one observer's description (the series X_n) with another's.

>Completely wrong. To compare descriptions of different observers
>is complicate enough in everyday life. Relativity is important in
>strong gravitational fields or for high velocities. Lorentz invariance
>is useful to prove some otherwise strange impossibility results
>(impossibility to measure absolute time) and otherwise useless.
>Proof: Lorentz-symmetric Maxwell theory was successful long
>before its Lorentz-symmetry has been observed.

There are two possibilities. One is that you paid too much attention
to my (probably inappropriate) use of the word "important", and
interpreted it as though I were saying that effects which are related
to relativity arise only in the circumstances that I was indicating;
and the other is that you feel as though you've scored a point when
you get to say things like "Completely wrong," and couldn't resist
doing so.

The point of the Lorentz transformations is to switch between one
observer and another, and the essence of relativity is that the
laws of physics are the same for different (inertial) observers,
even the speed of light. Without the idea of changing reference
points and considering things from a different observer's point
of view, special relativity would not have the formulation that
it does. In order to formulate the questions which relativity
addresses in my language, which is to some extent solipsistic,
one first has to address the question of what relationship
exists between one observer's X_n and another's X'_n, which
involves how one observer manifests himself within the X_n
of another, and that is a difficult question.

R.

Relevant Pages

  • Re: Lightspeed exceeded
    ... >>>The observer doesn't have this effect. ... The theory of relativity ... >This is essential to the difference between physics and mathematics. ...
    (sci.physics.relativity)
  • Re: Connes & Marcolli paper on renormalization
    ... Are you saying that momenta of particles are not observable in different ... > it is impossible for a physical observer to know the present anywhere ... > It has no direct physical meaning, but nevertheless general relativity ... >>My feeling is that theoretical physics is already in the dead end. ...
    (sci.physics.research)
  • Re: Sample of my SR model"s interpretation - first paradox
    ... relativistic effects with no counterparts in classical physics, ... It is obvious you understand little or nothing of relativity - it has ... By making the moving observer physically different, ...
    (sci.physics.relativity)
  • Re: Doppler shift vs second postulate
    ... If O (the observer) changes his velocity, ... Planck showed that light is generated in quantized lumps and Einstein showed that they were still in quantized lumps when they arrived at their destination It seems that at no time did the waves in aether of Maxwell's theory actually exist. ... Physics accepted relativity without looking at it carefully enough. ... You might think as I do that they should have scrapped it and started again, tried to find another way, but instead they got around this little difficulty by unilaterally deciding that a physical explanation is no longer a necessary part of a 'modern' physics theory. ...
    (sci.physics.relativity)
  • Re: Article: A Century of Einstein
    ... physics ideas, ... rotation between yourself and the stars. ... I know that its common for people trying to state Mach's Principle so ... rather than "absolute relativity". ...
    (sci.physics)