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ABSTRACT
The concept of time has been a
subject of speculation by philosophers for millennia. Only since the
late 1800s has it been the subject of serious investigation by physicists,
mainly in the study of irreversible thermodynamic processes and the theory
of relativity. My talk will be on the meaning of time in the quantum
domain, based on the informational interpretation of quantum mechanics
described in my last seminar. I argued then that pragmatic information—the
one and only which our brains can handle—is
a macroscopic, classical-world concept which does not operate in the
quantum domain. I now posit that the very concept of time, too, cannot
be defined in the quantum domain. The time variable in the Schrödinger
equation or in any propagation operator should be interpreted as the
macroscopic time, measured by a macroscopic clock,
at which the quantum system in question would cause a certain macroscopic
change (given by the equation’s solution) if it were to interact
with the macroscopic environment (or a measurement instrument).
We are used to the fact that for photons “time does not pass” (because
their world-lines are ds2 = 0 lines in 4-D space-time). So it should
not be too difficult getting used to the idea that, more generally, time
does not exist in any quantum system! I will show how this would explain
(i) why, given several unitarily interacting quantum systems, we must
describe them by a single composite state vector (a trick that’s
usually just taken as one of the QM postulates); (ii) why measurement
results on different components will be correlated, even if they are
far away from each other in macroscopic space and time (Einstein’s “spooky” correlation
without causation). But what about the decay of an unstable nucleus or
elementary particle—don’t they carry a teeny-weeny clock
inside? No, they don’t, as I will show.
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