What is the comparison between the Born rule and thermodynamics?

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    Born rule Thermodynamics
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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.

PREREQUISITES
  • Understanding of quantum mechanics, specifically the Born rule and statistical operators.
  • Familiarity with thermodynamics, particularly the grand-canonical ensemble and partition functions.
  • Knowledge of statistical mechanics and the concept of probability distributions in physical systems.
  • Basic grasp of coarse-graining and its implications in measurements.
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  • Research the implications of the Born rule in quantum mechanics and its applications in experimental setups.
  • Study the grand-canonical ensemble in thermodynamics and its statistical operator formulation.
  • Explore the concept of coarse-graining in statistical mechanics and its relevance to macroscopic measurements.
  • Investigate classical systems that exhibit probability distributions analogous to quantum interference patterns.
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Physicists, 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.

  • #91
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, ...?
 
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  • #92
Demystifier said:
I think such a question can be meaningfully asked only by using mathematical equations.

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.

So the question is.. what kind of information can be stored in the Hilbert space nonorthogonal states? How complex the information it can hold? Can they store a Barbie doll information? or nothing? just want to have idea...
 
  • #93
Demystifier said:
suppose that this trajectory can be explained theoretically by two different Hamiltonians

Is this possible? Can you give an actual example?
 
  • #94
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?

To be more conventional, one can use the term "expectation" in place of "average". Conceptually, there is no difference. You can see A. Neumaier's post #78 for the mathematical fine print.
 
  • #95
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.
 
  • #96
PeterDonis said:
Is this possible?
Yes.

PeterDonis said:
Can you give an actual example?
Solution ##x(t)=0##.
$$H_1=\frac{p^2}{2m}$$
$$H_2=\frac{p^2}{2m}+\frac{k x^2}{2}$$
 

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