The Causality Problem and Tunneling: An Overview

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    Causality Tunneling
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Discussion Overview

The discussion revolves around the concepts of causality and quantum tunneling, exploring the implications of tunneling as a quantum effect and its relationship to classical dynamics and causality. Participants delve into the nature of tunneling, particularly the non-zero probability of a particle passing through a potential barrier, and the conditions under which this phenomenon occurs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants describe tunneling as a quantum effect where a particle has a non-zero probability of passing through a potential barrier that is higher than its energy.
  • Others question the understanding of non-zero probability and finite width potential barriers, seeking clarification on these concepts.
  • It is noted that classically, a particle cannot penetrate a potential barrier if its energy is less than the barrier's height, but quantum mechanics allows for this possibility through tunneling.
  • A participant explains that the probability of tunneling can be interpreted as the likelihood of finding the particle in a specific region beyond the barrier, assuming the particle originates from negative infinity.
  • There is a distinction made between finite and infinite potential barriers, with implications for the discussion of tunneling versus the delta potential problem.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding tunneling and its associated probabilities, indicating that the discussion remains unresolved with multiple viewpoints and questions about the concepts presented.

Contextual Notes

Some assumptions about the definitions of tunneling and probability are not fully articulated, and the discussion does not resolve the complexities of causality in relation to quantum mechanics.

Phymath
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the causality problem and tunneling?
 
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Phymath said:
the causality problem and tunneling?

Tunelling is a quantum effect which consists in the existence of a non zero probability of that a point particle with energy E passes through a finite width potential barrier V(x)>E .

The causality of physical phenomena states that the effect cannot precede the cause.In classical dynamics,causality is questioned whenever forces that depend of the acceleration derivatives wrt to time appear.I would infer you to the analysis of the Abraham-Lorentz equation in the classical electrodynamics (can be found in Jackson...)

Daniel.
 
still unclear on the tunneling I am not fimilar with non zero probability (do u mean of being in a location?) and finte width potential Barrier
 
Phymath said:
still unclear on the tunneling I am not fimilar with non zero probability (do u mean of being in a location?) and finte width potential Barrier

Classically,the particle has no chance to penetrate that potential barrier,as its energy is less than the barrier's.But QM proves that this becomes possible (has a non zero probability (do u know what probabilities are...?)) once the system is quantized.Yes,the probability of passing through could be seen as the probability of finding the particle anywhere in the semiinfinite interval between the point at which the particle exits the potential barrier and the +infinity on the axis describing the direction of movement.I assumed the particle comes from -infinity.That's why the potential barrier must be finite,both as width and as height.If it wasn't finite along the "x" axis (if it didn't have a finite width),we would not be speaking about the tunnel effect.If it were infinitely height,we would not speak about tunnel effect,but about "delta potential problem".

I hope it's clear.
 

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