Bohmian Trajectories: Intersections & Young Experiments

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Discussion Overview

The discussion revolves around Bohmian trajectories, particularly their behavior in relation to intersections and implications in the context of Young's experiments. Participants explore the nature of these trajectories, their representation in space-time, and the conditions under which they may or may not intersect.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that a Bohmian trajectory cannot intersect itself due to the dependence of speed on position, particularly in the context of a particle trapped by a potential.
  • There is a distinction made between intersections in space-time versus 3-space, with some arguing that crossing the same spatial point at different times does not constitute an intersection in space-time.
  • One participant questions whether two trajectories can be very close without intersecting and whether there is a force that repels them, drawing a parallel to the Fermi exclusion principle.
  • Another participant notes that the inability for trajectories to intersect is not unique to Bohmian mechanics but applies to any well-behaved initial-value problem in differential equations.
  • There is a mention of geodesics being able to meet, contrasting with Bohmian trajectories, and a reference to Bohm's writings regarding boundary conditions in equations of motion.
  • Participants discuss the possibility of two points in a small neighborhood having orthogonal momentums, with some suggesting that if the neighborhood is not of zero size, there are no inherent restrictions.
  • Questions arise about specific momentum configurations at time t = 0, with one participant proposing a scenario that is met with a definitive "no" from another.

Areas of Agreement / Disagreement

Participants express differing views on the nature of intersections of Bohmian trajectories, with some asserting that they cannot intersect while others explore the conditions under which they might be close without intersecting. The discussion remains unresolved regarding the implications of these trajectories in specific scenarios.

Contextual Notes

Participants reference various theoretical concepts and principles, such as boundary conditions and the Fermi exclusion principle, which may introduce limitations or assumptions that are not fully explored in the discussion.

PaleMoon
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i read that a bohmian trajectory (in this interpretation) cannot intersect itself because the speed depends on the position. there is no visualization problem in a Young experiment with trajectories from the slits to the screen.
it becomes harder when a particle is trapped in a small region by a potential which make it remain there a long time before a possible tunnelling. how does it work then?
 
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PaleMoon said:
i read that a bohmian trajectory (in this interpretation) cannot intersect itself because the speed depends on the position. there is no visualization problem in a Young experiment with trajectories from the slits to the screen.
it becomes harder when a particle is trapped in a small region by a potential which make it remain there a long time before a possible tunnelling. how does it work then?
The trajectory is considered in space-time, not in 3-space. Crossing the same space point at different times is not an intersection in space-time.
 
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A. Neumaier said:
The trajectory is considered in space-time, not in 3-space. Crossing the same space point at different times is not an intersection in space-time.
Exactly!
 
I am sorry. my question was very incorrectly asked.
i wonder why in bohmian model two different trajectories cannot intersect. i know that the speed
at one point in space time only depends on the configuration space point and that intersection of two curves would be a problem. but can two such trajectories be very very close without problem?
is there some force repelling them. (i have the same problem with fermi exclusion principle when the positions only differ by an infinitesimally small distance)
 
PaleMoon said:
why in bohmian model two different trajectories cannot intersect.
This is not special to Bohmian mechanics; it holds for any reasonably well-behaved initial-value problem for differential equations. Read some introductory literature about dynamical systems and the phase diagrams representing their flow!
 
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Geodesics can meet. Bohmian trajectories cannot.

Bohm himself writes this

It is in connection with the boundary conditions appearing in the equations of motion that
we find the only fundamental difference between the psi-field and other fields such as electromagnetism
 
please read the bottom of page 5 in Bohm's paper
i repeat my question.
Is there something that prevent two points in a small neighborhood to have orthogonal momentums (2 different trajectoiries might be tangent if they meet and exist!)
 
PaleMoon said:
Is there something that prevent two points in a small neighborhood to have orthogonal momentums
If the neighborhood has not a zero size, then nothing prevents it.
 
is it possible a t = 0 that all the momentums are equal to p = 1_x> (unitary ane parallel to x) except in the plane y = o where the momentum would be 1_z> ?
 
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PaleMoon said:
is it possible a t = 0 that all the momentums are equal to p = 1_x> (unitary ane parallel to x) except in the plane y = o where the momentum would be 1_z> ?
No.
 
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  • #11
Oh yes i see now but can you elaborate?
 
  • #12
PaleMoon said:
Oh yes i see now but can you elaborate?
If you see it, then why do you need need an elaboration?
 

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