Plotting the approximation of the Dirac delta function

In summary, the article discusses methods for approximating the Dirac delta function using various mathematical techniques, such as sequences of functions that converge to the delta function. It highlights the importance of these approximations in fields like physics and engineering, where the delta function is used to model point sources and impulse responses. The article also provides visual representations of different approximations, illustrating their convergence to the Dirac delta function in the limit.
  • #1
Lambda96
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Homework Statement
Plot ##g^{\epsilon}(x)## for ##\epsilon=1## , ##\epsilon=\frac{1}{2}## and ##\epsilon=\frac{1}{4}##
Relevant Equations
none
Hi,

I am not sure if I have solved the following task correctly

Bildschirmfoto 2024-01-15 um 16.34.11.png


I did the plotting in mathematica and got the following

Bildschirmfoto 2024-01-15 um 16.48.02.png

Would the plots be correct? What is meant by check for normalization, is the following meant?

For the approximation for ##\epsilon > 0##, does it mean that for the area of ## 0 < x < \epsilon## the area must be 1, so for the case ##\epsilon=1## the total area would be 1, the half for ## 0 < x < \epsilon## would then be ##\frac{1}{2}##, so the normalization constant should be 2?
 
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  • #2
To sketch usually means to draw by hand. Is this behavior that you expected? Look at the formula. Between minus epsilon and +epsilon, what is the function doing (does it change with x)?

Normalization refers to the area under the "curve" equal to 1 over the entire spectrum. Do these graphs satisfy that?
 
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  • #3
Lambda96 said:
Would the plots be correct?
Yes, those plots look correct.
Lambda96 said:
What is meant by check for normalization, is the following meant?
It means to check that the integral is 1.
Lambda96 said:
For the approximation for ##\epsilon > 0##, does it mean that for the area of ## 0 < x < \epsilon## the area must be 1,
No. It means that the area of ##- \epsilon < x < \epsilon ## must be 1.
Lambda96 said:
so for the case ##\epsilon=1## the total area would be 1, the half for ## 0 < x < \epsilon## would then be ##\frac{1}{2}##, so the normalization constant should be 2?
No. No further normalization is needed. The area between each graph and the x axis is already 1.
 
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  • #4
Thank you scottdave and FactChecker for your help 👍👍
 
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FAQ: Plotting the approximation of the Dirac delta function

What is the Dirac delta function?

The Dirac delta function, often represented as δ(x), is a mathematical construct that is not a function in the traditional sense but rather a distribution. It is defined to be zero everywhere except at x = 0, where it is infinitely high such that its integral over the entire real line is equal to one. It is used to model an idealized point mass or point charge in physics and engineering.

How can the Dirac delta function be approximated for plotting?

The Dirac delta function can be approximated using various functions that become increasingly narrow and tall as a parameter approaches a limit. Common approximations include the Gaussian function, the Lorentzian function, and the sinc function. For example, a Gaussian function with mean zero and variance approaching zero can be used to approximate the delta function.

Why is it important to approximate the Dirac delta function?

Approximating the Dirac delta function is important because it allows for practical numerical computations and visualizations. In many applications, such as signal processing and differential equations, exact representations of the delta function are not possible, so approximations are used to analyze and interpret results.

What are the challenges in plotting the Dirac delta function?

One of the main challenges in plotting the Dirac delta function is its nature of being zero everywhere except at a single point where it is infinitely high. This makes it impossible to represent exactly on a standard plot. Instead, approximations must be used, and care must be taken to choose an appropriate scale and resolution to convey the behavior of the approximation effectively.

Can you provide an example of a Python code to plot an approximation of the Dirac delta function?

Sure! Here is an example using a Gaussian approximation in Python with the Matplotlib library:

import numpy as npimport matplotlib.pyplot as plt# Define the Gaussian approximation of the Dirac delta functiondef gaussian_delta(x, epsilon):    return np.exp(-x**2 / (2 * epsilon**2)) / (epsilon * np.sqrt(2 * np.pi))# Define the range and parameter for the approximationx = np.linspace(-1, 1, 1000)epsilon = 0.01# Calculate the Gaussian approximationy = gaussian_delta(x, epsilon)# Plot the approximationplt.plot(x, y)plt.title('Gaussian Approximation of the Dirac Delta Function')plt.xlabel('x')plt.ylabel('δ(x)')plt.show()
This code defines a Gaussian function as an approximation of the Dirac delta function and plots it over a specified range.

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