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Demystifier said:Consider a physical system in which the average value of position is ##<x>=0##. What is the probability that the position is ##x=1## nm?
But if you also know \langle x^2 \rangle, \langle x^3 \rangle, ...?
The discussion centers on the analogy between the Born rule in quantum mechanics and concepts in thermodynamics, particularly regarding the statistical operator and probability distributions. The Born rule, expressed as $$\langle A \rangle = \mathrm{Tr} (\hat{\rho} \hat{A})$$, relates to measurement outcomes in quantum systems, while in thermodynamics, the statistical operator for the grand-canonical ensemble is given by $$\hat{\rho}=\frac{1}{Z} \exp[-\beta (\hat{H}-\sum_j \mu_j \hat{Q}_j)]$$. Participants explore how classical systems can exhibit regions of varying probabilities similar to quantum interference patterns, emphasizing the need for conceptual illustrations over dense mathematical formulations. The conversation also touches on the implications of coarse-graining and the differences between macroscopic and microscopic measurements.
PREREQUISITESPhysicists, particularly those specializing in quantum mechanics and thermodynamics, as well as researchers interested in the foundational aspects of statistical mechanics and the interplay between classical and quantum systems.
Demystifier said:Consider a physical system in which the average value of position is ##<x>=0##. What is the probability that the position is ##x=1## nm?
Demystifier said:I think such a question can be meaningfully asked only by using mathematical equations.
Demystifier said:suppose that this trajectory can be explained theoretically by two different Hamiltonians
Demystifier said:Consider a physical system in which the average value of position is ##<x>=0##. What is the probability that the position is ##x=1## nm?
Yes.Blue Scallop said:Ok, mathematically.. if we remove the position basis.. then there would be no decoherence and no subsystems if there are no other basis to define it. And it's back to pure Hilbert space vectors with unit trace 1.
Yes.PeterDonis said:Is this possible?
Solution ##x(t)=0##.PeterDonis said:Can you give an actual example?