Why particle in a box is considered as 1-dimensional ?

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Discussion Overview

The discussion revolves around the dimensionality of the particle in a box model in quantum mechanics, specifically addressing why it is considered one-dimensional despite the sine curve representation suggesting multiple coordinates. Participants explore the implications of dimensionality in relation to probability and movement within the box.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions why the particle in a box is considered one-dimensional, noting that a sine curve requires two coordinates for its representation.
  • Another participant asserts that the particle only moves left and right along the x-axis, clarifying that the sine curve represents probability rather than spatial dimensions.
  • A follow-up comment emphasizes that the focus is on the x-axis for determining the particle's position, despite its movement in space.
  • One participant uses the analogy of a bead on a string to illustrate that the particle's movement is restricted to left and right, reinforcing the one-dimensional perspective.
  • Another participant explains that the vertical axis in the graph represents probability amplitude, not a spatial direction, further distinguishing between graphical representation and physical movement.
  • A later reply discusses the dependence of the Hamiltonian on dimensionality, noting that a one-dimensional Hamiltonian leads to solutions based on a single coordinate, while a three-dimensional case would involve multiple coordinates and potential energy considerations.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of dimensionality in the particle in a box model. While some argue for a strict one-dimensional perspective based on movement and probability, others raise questions about the implications of the sine curve representation, indicating that the discussion remains unresolved.

Contextual Notes

The discussion highlights the complexity of defining dimensionality in quantum mechanics, with references to potential energy and the form of solutions depending on the specific problems considered. There are unresolved assumptions regarding the interpretation of the sine curve and its relation to spatial dimensions.

dying_star
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I'm new to the field of quantum mechanics and I have got this basic doubt.
The position of the particle in a box is defined by the sine curve. Any position on a sine curve requires 2 coordinates to get the location of the particle having the highest probability at any point of time.
But why is it considered as single dimension ?
(The particle is free to move in the left or right direction, but as we define it by a sine curve it can also move up and down.)
 
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No, it doesn't move up and down. It moves only left and right, and solution doesn't tell you what is particle's position in terms of (x,y), but what is probability of finding it along x axis.
 
Do you mean that even if the particle moves in space inside the box, we are interested to know the position with respect top X -axis.
 
It is like a bead on a string - it can move only left and right. Thus only x axis.
 
The vertical axis of the graph is the probability amplitude, not the spatial direction.
It's a graph, not a picture of the box.

It's the same as if you made a graph of the speed of a car starting down a road and stopping. The graph goes up and down - but the car doesn't. The road is one-dimensional.
 
If it is used 1-dimensional hamiltonian then the solution depends on 1 coordinate x.
If 3-dimensional then f(x,y,z) is obtained.
It depends on the potential energy if the solution is the product of separate functions
f(x,y,z)=f1(x)f2(y)f3(z).
Sometimes the form of separate functions is the same and
f(x,y,z)=g(x)g(y)g(z).
So if g(x) is known the 3-dimensional function is known too.
It depends on the definite problems under consideration.
 

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