Some questions about time and causality in the MWI

In summary, the speaker is asking about the concept of time and causality in the Many-Worlds Interpretation (MWI) of quantum mechanics. They question how decoherence, which is the loss of quantum coherence due to interaction with the environment, does not contradict the evolution of the wavefunction in multiple worlds. They also wonder if time is absolute in each world in the MWI, and if the wavefunction is seen as multiple entities in each world or one entity dictating the behavior of all worlds. The expert summarizer responds by explaining that causality is preserved in each world in the same way as in other interpretations of quantum mechanics, and that the wavefunction at a certain time depends on the wavefunction at earlier times. They
  • #1
Posy McPostface
Forgive my novice question; but, how does one explain the fact that decoherence doesn't contradict the evolution of the wavefunction in every world? Meaning, how is causality preserved in each world and what concept of time is professed wrt. to each world in the MWI? In other words, it seems like time is absolute and not relative with respect to each world in the MWI and decoherence being able to happen at all. Or am I understanding the wavefunction wrong here, as if it were multiple entities existing in each world and not one dictating the behavior of all worlds?
 
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  • #2
What do you mean by "contradict the evolution of the wavefunction"?
Meaning, how is causality preserved in each world
It does't make much sense to talk about a single world if you want to look at time evolution. Anyway: The same way it is preserved in nearly all interpretations. The wave function at time T depends on the wave function at times t<T only.
Posy McPostface said:
In other words, it seems like time is absolute and not relative with respect to each world in the MWI
What would "relative with respect to each world" mean?
Posy McPostface said:
Or am I understanding the wavefunction wrong here, as if it were multiple entities existing in each world and not one dictating the behavior of all worlds?
I don't understand that question.
 
  • #3
Nevermind, please disregard.

Thanks.
 
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Likes jim mcnamara

FAQ: Some questions about time and causality in the MWI

1. What is the Many-Worlds Interpretation (MWI) of quantum mechanics?

The MWI is a theory proposed by physicist Hugh Everett in the 1950s to explain the behavior of particles on a microscopic level. It suggests that every time a quantum measurement is made, the universe splits into multiple parallel universes, each containing a different outcome of the measurement. This means that all possible outcomes of a measurement exist simultaneously in their own separate world.

2. How does the MWI address the concept of time in quantum mechanics?

The MWI does not view time as a linear progression, but rather as a series of parallel universes branching out from each other at every moment. This means that all possible past, present, and future states of the universe exist simultaneously.

3. Does the MWI provide an explanation for the concept of causality?

The MWI suggests that causality is not a fundamental aspect of reality, but rather a result of our limited perspective. In the MWI, all events are seen as equally real and causality is merely a human construct used to make sense of our experiences in a single universe.

4. Are there any experiments or evidence that support the MWI?

At this point, the MWI remains a theoretical interpretation of quantum mechanics and has not been proven or disproven by any experiments. However, some physicists argue that the MWI can provide a more elegant explanation for certain quantum phenomena, such as the double-slit experiment.

5. How does the MWI differ from other interpretations of quantum mechanics?

The MWI differs from other interpretations, such as the Copenhagen interpretation, in that it does not require an observer to collapse the wave function. It also differs from the pilot-wave theory, which suggests that particles have definite positions and behave deterministically. The MWI proposes that all possible outcomes of a measurement exist simultaneously, while other interpretations may only consider a single outcome as the "true" reality.

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