Which of these interpretations of the modulus squared of wavefunction is right?

Click For Summary

Discussion Overview

The discussion revolves around the interpretation of the modulus squared of the wavefunction, specifically whether |\psi(\mathbf{x},t)|^2d^3\mathbf{x} or |\psi(\mathbf{x},t)|^2d^3\mathbf{x}dt should be used to determine the probability of a particle collapsing at a point \mathbf{x} at time t. The scope includes theoretical interpretations and implications in quantum mechanics.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that |\psi(\mathbf{x},t)|^2d^3\mathbf{x} is the correct form for determining the probability at a specific time, arguing that integrating over time does not make sense.
  • Others express concerns about treating space and time differently in nonrelativistic quantum mechanics, suggesting that this distinction complicates the interpretation.
  • One participant points out that while the probability of a Geiger counter registering a count at an exact time t is zero, the probability over a time interval is non-zero, raising questions about the application of Born's rule.
  • Another participant argues that the probability given by |\psi^2|dV should not be directly used to predict the frequency of counts from a Geiger detector without considering the source intensity.
  • It is noted that a normalized wave function provides the probability density in space, independent of detection, and that the number of counts from a detector is proportional to the time interval of measurement due to the presence of distinct particles.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct interpretation of the modulus squared of the wavefunction, with multiple competing views and unresolved questions regarding the treatment of space and time in quantum mechanics.

Contextual Notes

The discussion highlights limitations in the interpretation of quantum mechanics, particularly regarding the assumptions about the relationship between space and time, and the implications of using Born's rule in practical measurements.

dEdt
Messages
286
Reaction score
2
Does [itex]|\psi(\mathbf{x},t)|^2d^3\mathbf{x}[/itex] or [itex]|\psi(\mathbf{x},t)|^2d^3\mathbf{x}dt[/itex] give the probability of a particle to collapse at the point [itex]\mathbf{x}[/itex] at time [itex]t[/itex]?

Griffiths sides with the former, but I'm having doubts.
 
Physics news on Phys.org
dEdt said:
Does [itex]|\psi(\mathbf{x},t)|^2d^3\mathbf{x}[/itex] or [itex]|\psi(\mathbf{x},t)|^2d^3\mathbf{x}dt[/itex] give the probability of a particle to collapse at the point [itex]\mathbf{x}[/itex] at time [itex]t[/itex]?

Griffiths sides with the former, but I'm having doubts.

It's the former, it doesn't make sense to integrate over time, at any instant t, the integration over space gives you the overall probability at that time, which is 1.
 
cattlecattle said:
It's the former, it doesn't make sense to integrate over time, at any instant t, the integration over space gives you the overall probability at that time, which is 1.

Here are my issues: 1) space and time seem to be treated on different footings, and 2) the probability that say a Geiger counter goes off at a given time t is zero, but the probability that it goes off over some time interval is non-zero.
 
dEdt said:
Here are my issues: 1) space and time seem to be treated on different footings,

Yes. This is nonrelativistic quantum mechanics, which treats space and time differently. To fix this we have relativistic quantum field theory.

dEdt said:
2) the probability that say a Geiger counter goes off at a given time t is zero, but the probability that it goes off over some time interval is non-zero.

If you do an ideal position measurement at time t, the probability of finding the particle *somwhere* is 1. Geiger counters don't do ideal position measurements; the quantum mechanical analysis of radioactive decay is somewhat more complicated.
 
2) the probability that say a Geiger counter goes off at a given time t is zero, but the probability that it goes off over some time interval is non-zero.

This is true, but I think the probability given by [itex]|\psi^2|dV[/itex] according to Born's interpretation should not be used directly to predict the frequency of counts of the Geiger detector (unless one smuggles the source intensity to [itex]\psi[/itex], which can allow us to do just that; but then the above form of Born's rule is not applicable.)

Instead, if the wave function for a particle is normalized (the most clear approach), it gives us the probability that this particle is at some point of space (without the necessity to detect it there).

You are right that the number of counts(clicks) of detector set in some definite distance from the piece of matter scattering charged particles will be proportional to time interval of the measurement, but this is because larger interval allows more [itex]\textit{distinct particles}[/itex] to come at the detector; however, each one can be ascribed by normalized wave function that gives density of probability in space by the rule [itex]|\psi|^2dV[/itex].
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
19
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 309 ·
11
Replies
309
Views
17K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 0 ·
Replies
0
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 84 ·
3
Replies
84
Views
7K