Finding general expression for probability current.

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Homework Help Overview

The discussion revolves around finding a general expression for the probability current in the context of quantum mechanics, specifically using the Schrödinger equation and the conservation of probability. The original poster expresses confusion regarding the notation and the mathematical framework involved.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster seeks clarification on the notation used in the conservation of probability equation and its implications. Some participants inquire about specific terms and their meanings, such as the partial derivatives and the choice of Schrödinger equation to use. Others provide explanations of the notation and its traditional interpretations.

Discussion Status

The discussion is ongoing, with participants providing clarifications on the notation and its meaning. There is an indication that the original poster will revisit the provided information to further their understanding.

Contextual Notes

Participants are navigating the complexities of quantum mechanics notation and the implications of using different forms of the Schrödinger equation. The original poster has expressed a lack of familiarity with the notation, which may affect their ability to engage with the problem effectively.

David Silva
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The conservation of probability says:

$$\partial_t J^{0} + \partial{i}J^{i} = 0$$

Use the Schrödinger equation to obtain$$ J^{i} (\vec r)$$.

I have no idea where to start this kind of problem because the notation makes no sense to me. I would appreciate a hint or nudge in the correct direction.
 
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What about the notation confuses you?
 
vela said:
What about the notation confuses you?
What do those partials mean? I am not used to seeing them this way? Also would I be using the general SE eq or the radial one since we are in r?
 
Typically ##x^0 = t##, ##x^1 = x##, ##x^2 = y##, and ##x^3 = z##, so ##\partial_1## would mean ##\partial_x##. The repeated index ##i## implies a summation from ##i=1## to ##i=3##.

You have ##J^\mu = (\rho,J_x, J_y, J_z)##, so in more traditional notation, conservation of probability is
$$\frac{\partial \rho}{\partial t} + \nabla \cdot \vec{j} = 0$$ where ##\vec{j} = (J_x, J_y, J_z)##.
 
vela said:
Typically ##x^0 = t##, ##x^1 = x##, ##x^2 = y##, and ##x^3 = z##, so ##\partial_1## would mean ##\partial_x##. The repeated index ##i## implies a summation from ##i=1## to ##i=3##.

You have ##J^\mu = (\rho,J_x, J_y, J_z)##, so in more traditional notation, conservation of probability is
$$\frac{\partial \rho}{\partial t} + \nabla \cdot \vec{j} = 0$$ where ##\vec{j} = (J_x, J_y, J_z)##.

Thanks, I will look at this later today and see if it helps!
 

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