What is the comparison between the Born rule and thermodynamics?

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    Born rule Thermodynamics
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Discussion Overview

The discussion explores the analogy between the Born rule in quantum mechanics and concepts in thermodynamics, particularly focusing on how probabilities are represented in both frameworks. Participants examine the implications of these analogies, the mathematical formulations involved, and seek examples of thermodynamic systems that exhibit similar probabilistic behavior as seen in quantum mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that the Born rule's probabilistic nature in quantum mechanics has an analogy in thermodynamics, questioning what the counterpart of the Born rule might be in thermodynamic systems.
  • One participant provides the mathematical formulation of the Born rule and its application in quantum mechanics, emphasizing the statistical operator's role.
  • Another participant challenges the terminology used, asserting that the term "Born rule" is misapplied and should relate specifically to measurement results and eigenvalues.
  • A participant references an article discussing the analogy between quantum mechanics and classical systems, particularly in the context of Brownian motion and information loss, suggesting that classical systems may exhibit probabilistic behavior akin to quantum systems.
  • In the context of the double slit experiment, a participant asks for examples of thermodynamic systems that display regions of higher and lower probabilities, similar to interference patterns.
  • There is a discussion about the differences between the general Born rule and its application to individual measurements, with some participants expressing a desire to understand the implications for macroscopic observables.
  • Some participants highlight the importance of statistical independence in measuring expectation values in ensembles, contrasting this with individual measurements in quantum mechanics.

Areas of Agreement / Disagreement

Participants express differing views on the applicability and interpretation of the Born rule in relation to thermodynamics. There is no consensus on whether the analogy holds or how to define the counterpart in thermodynamics. The discussion remains unresolved regarding the specific examples of thermodynamic systems that exhibit probabilistic behavior similar to quantum mechanics.

Contextual Notes

Participants note the limitations of their arguments, including the need for clearer definitions and the potential dependence on specific assumptions about the systems being discussed. The mathematical formulations presented may also depend on the context in which they are applied.

  • #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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