Multiple Levels `Inside' Quantum Physics?
Ian Thompson, University of Surrey
26th Sept 2000
There are a number of `features' of QM that are apparently ad hoc
and not readily understood:
- Does anything actually happen? Are
there actual events independent of our immediate experience? (The measurement problem)
- Does anything exist in the physical world? (The substance problem)
- What do wave functions describe? (The same problem again)
- Are all measurements really position measurements, even though
precise positions are never measured! (The preferred basis problem)
- Are actual and virtual events the same or different?
- Are all events really interactions?
I will work towards presenting a framework of `multiple generative
levels', in which I believe more sense can be made of all these disparate
aspects of quantum mechanics and how they are related. I want to give a
`realist' view, which describes what wave functions describe,
what really goes on in nature, and how nature `works out what to do'.
First some explanation of concepts:
- Multiple generative levels
- are a sequence
in which A `generates' or `produces' new forms of Busing the present form of B as a precondition. Then B generates C in
the same way, and so on until the end where nothing is active.
- In order for any A to generate anything, it must be
something like a `cause' or `propensity' or `potential'.
Forces are like this: they do not
say what does happen: a specification of a force says what
(acceleration) would be caused if a mass was acted on.
Electric fields are
like this: a field strength generates a force when a charge is
Quantum wave functions are like this: they generate probabilities if
and only if a `measurement' is made.
- Multilevel Propensities
are `parallel processes' all equally real.
Level B, for example, is
not just an approximate description of successive forms of other levels
A or C, neither is it a microscopic constituent of either of
those levels. Rather, levels A, B, C,... are to be regarded as real
processes `in parallel' that interact with other by relations of `generation' and
Initially, I propose three generative levels:
an actual event is the selection of a specific `historical alternative'
from among finitely many alternative configurations, the selection being generated by a `propensity to select',
according to Born's probability rule.
- A `propensity to select' is the `propensity wave'
(better known as the `wave
function', or `wave packet' or `probability amplitude').
`Propensity waves in configuration space' are the best way of
viewing particles as quantum substances.
- A `propensity wave' at a particular time is generated from its form at a
previous time by the operation of the Energy Operator (better known as the
Hamiltonian) according to Schrödinger's equation
But where does the Hamiltonian come from? We cannot just invent it!
We know that the potential energy part of the Hamiltonian really comes from
field-theoretic virtual processes. Where are these events?
In more detail, I propose two linked sets of three generative levels each :
where the two sets have (broadly) corresponding processes at each level
(as shown by dotted lines):
- Virtual Outcomes are the `virtual events' of quantum field theory,
that generate the potential energy part of the Hamiltonian.
They do not all `actually occur' because, for example, they may generate potentials
that are never active in the selected sequence of actual outcomes.
- Propagating field quanta (virtual quantum substances)
generate virtual events when interacting.
- The field-theoretic Lagrangian functional is where this generative sequence starts off,
as the virtual field propagation equations are derived from it according
to a Variational Principle.
I hope that this classification of several `stages' in nature, as seen in
quantum mechanics, may help in a small way to understand quantum
physics and what really goes on.
Prof Ian Thompson