How to determine a Limits of Integration of Wave Packet

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Homework Help Overview

The discussion revolves around determining the limits of integration for a wave packet representing a force-free particle. The wave packet is defined piecewise, with different expressions for various intervals of the variable x, and the goal is to find the normalization constant A as part of calculating mean values and variances of position and momentum operators.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the need to break down the integral into segments corresponding to the defined intervals of the wave packet. Questions arise regarding the appropriate limits for integration, particularly for the segment where the wave function is constant.

Discussion Status

The conversation is ongoing, with participants exploring different interpretations of the integration limits. Some guidance has been offered regarding the necessity of considering all intervals, but explicit consensus on the limits has not been reached.

Contextual Notes

Participants are grappling with the piecewise nature of the wave packet and the implications for integration. There is uncertainty about how to handle the first integral and whether it should be included in the calculations.

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Homework Statement


Consider a force-free particle of mass m described, at an instant of time t = 0, by
the following wave packet:
<br /> \begin{array}{l}<br /> 0 \ \mathrm{for} \ |x| &gt; a + \epsilon \\<br /> A \ \mathrm{for} \ |x| ≤ a \\<br /> -\frac{A}{\epsilon} (x − a − \epsilon) \ \mathrm{for} \ a &lt; x ≤ a + \epsilon \\<br /> \frac{A}{\epsilon}(x + a + \epsilon) \ \mathrm{for} \ − a − \epsilon ≤ x &lt; a \\<br /> \end{array}<br />
where a, ε, and a normalization constant A are all positive numbers. Calculate mean
values and variances of the position and momentum operators x , x^{2} , \sigma_{x} \ and \ p_{x} .

Homework Equations


<br /> 1=\int_{-\infty}^{\infty} |\psi(x,t)|^{2}<br />

The Attempt at a Solution


I want to determine normalization constant A. I don't know what kind of integration limits i should use for the case:
A \ \mathrm{for} \ |x| ≤ a.
Do you have any ideas ? Thanks in advance !
 
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You have a lot of intervals and need to use the fact that the integral will be a sum of integrals for each interval. So write all the integrals, compute them all the find A. Then compute all other items.
 
Ok , so far i have:
\int_{??}^{??} A^{2} dx (?) -\frac{A^{2}}{\epsilon^{2}}\int_{a}^{a+\epsilon} (x-a-\epsilon)^{2} dx +\frac{A^{2}}{\epsilon^{2}}\int_{-a-\epsilon}^{a} (x+a+\epsilon)^{2} dx =1. My question is what are the integration limits for the first integral ?
 
Where did you pick the first one from ? Is there an interval where the wavefunction is 1 ?
 
So, should i include first integral ? That was my problem/question ?
 

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