[Home]Everett many-worlds interpretation

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Difference (from prior major revision) (minor diff, author diff)

Changed: 1,12c1,2
Paraphrased from question 2 (What is many-worlds?) of
http://www.hedweb.com/manworld.htm since I'm not sure the
original author would agree to the GNU FDL. What follows is
therefore subject to the possibility of misinterpretation on
my part.


This interpretation originated with Hugh Everett III's 1956
paper, "The Theory of the Universal Wavefunction, Princeton
thesis", which appears in the book The Many-worlds Interpretation of Quantum Mechanics, Bryce S DeWitt?,
R Neill Graham, eds, Princeton Series in Physics, Princeton
University Press (1973) ISBN 0-691-08126-3 (amazon.com, search) (hard cover),
ISBN 0-691-88131-X (amazon.com, search) (paper back). The phrase "many worlds" is due

This interpretation of quantum mechanics originated with Hugh Everett III in 1956.
The phrase "many worlds" is due

Changed: 19c9
unlike the Copenhagen interpretation which considers the
unlike the Copenhagen interpretation which considers the

Changed: 21,25c11,12
interpretation, the Schrodinger wave equation holds all
the time everywhere. (Perhaps this means
that wavefunction collapse represents some kind of transient
violation of the wave equation? My knowledge of quantum
mechanics is way too shallow to answer that.)
interpretation, the Schrödinger wave equation holds all
the time everywhere.

Changed: 29c16
modelled by applying the Schrodinger wave equation to the
modelled by applying the Schrödinger wave equation to the

Changed: 31,33c18
consequence is that every observation (a thermodynamically
irreversible process) causes the universal wavefunction to
decohere into two or more non-interacting branches. Since
consequence is that every observation causes the universal wavefunction to decohere into two or more non-interacting branches, or "worlds". Since

Changed: 43c28
entangled and it is no longer possible to consider them
entangled and it is no longer possible to consider them

Added: 54a40,45



References:
* "The Many-worlds Interpretation of Quantum Mechanics" by Bryce S DeWitt?, R Neill Graham, eds, Princeton Series in Physics, Princeton University Press (1973)
* [Michael Price's Everett FAQ]


This interpretation of quantum mechanics originated with Hugh Everett III in 1956. The phrase "many worlds" is due to Bryce DeWitt?, who wrote more on the topic.

There are two assumptions underlying the many-worlds view. The first is that the wavefunction is not simply a description of the object's state, but that it actually is the object. The second is that observation has no special role, unlike the Copenhagen interpretation which considers the wavefunction to collapse upon observation. Under the many-worlds interpretation, the Schrödinger wave equation holds all the time everywhere.

Various consequences follow from these assumptions. An observation or measurement of an object by an observer is modelled by applying the Schrödinger wave equation to the entire system comprising the observer and the object. One consequence is that every observation causes the universal wavefunction to decohere into two or more non-interacting branches, or "worlds". Since many observation-like events are constantly happening, there are an enormous number of simultaneously existing worlds.

If a system is comprised of two or more subsystems, the system's state will typically be a superposition of products of the subsystems' states. Once the subsystems interact, their states are no longer independent. Each product of subsystem states in the overall superposition evolves over time independently of other products. The subsystems have become entangled and it is no longer possible to consider them independent of one another. Everett's term for this entanglement of subsystem states was a relative state, since each subsystem must now be considered relative to the other subsystems with which it has interacted.

Mathematically and physically, the many-worlds interpretation is simpler than the more widely accepted Copenhagen interpretation. The act of observation or measurement is not magical, and the interpretation of probabilities as the squared amplitude of the wave function is a direct consequence of the theory rather than a necessary axiom.


References:


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