X-Message-Number: 21027
From: "michaelprice" <>
References: <>
Subject: Robustness of quantum theory
Date: Sat, 1 Feb 2003 00:13:45 -0000

Thomas Donaldson wrote:

> For Michael Price about identity of particles:
> It is not that we would somehow return to some former theory but
> that we would find another better one.

I'm not quite sure where I implied we might return to a former theory, or
that we might not find a better one.  All I'm suggesting is that quantum
theory is sufficiently well established for its core concepts, such as
particle identity, to survive, just as the basic Newtonian concepts of mass,
force, momentum and energy have been incorporated into both relativity and
quantum mechanics.

> Already, as you know,
> protons aren't thought of as single identities but as composed
> of quarks. At least some have suggested an improvement on the
> quark theory which leads to seeing electrons as composed entities
> also. Or are they special features of a theory using 15 dimensions
> of which all but 4 collapse tightly?

The example you give suggests that particle identity is a robust concept.
Protons (and atoms) have an internal structure (quarks for protons, as you
point out), yet they are demonstrably identical to each other (i.e. they
quantum interfere as per previous discussion).  By analogy, an electron's
internal or deeper structure (as string/m-theory suggests) is irrelevant to
its identity ; our present concepts of atomic and sub-atomic identity seem
robust enough to survive future advances.

> I am pointing out that right now we don't even know that our
> ideas on the identity of electrons will survive when we work
> out how to combine relativity with quantum mechanics.

I assume you mean general relativity = gravity, since special relativity
(E=MC2) already has been unified with both quantum mechanics and field
theory to produce relativistic quantum field theories, such as quantum

It is noteworthy that all credible attempts (that I am aware of) to unify
relativistic quantum field theory with general relativity are still quantum
theories (hence the term quantum gravity).  This is another indication of
the robustness of quantum theory and our notions of particle identity.

Michael C Price

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