Limit involving dirac delta distributions

In summary, the conversation is about evaluating the limit of the second derivative of the Dirac distribution as x approaches 0, and the speaker is wondering if this limit is impossible to evaluate due to the nature of the Dirac distribution. They also mention the idea of using L'Hospital's rule and possibly writing the delta function as a limit of a Gaussian.
  • #1
thrillhouse86
80
0
Hey All,

I am trying to evaluate the limit:
[tex]
\lim_{x\to 0^{+}} \frac{\delta''(x)}{\delta''(x)}
[/tex]

Where [tex] \delta'(x) [/tex] is the first derivative of the dirac distribution and [tex] \delta''(x) [/tex] is the second derivative of the dirac distribution.

I thought about the fact that this expression will be infinity / infinity and then using L'Hospitals but that doesn't help.

I guess my question (as someone with an engineering / physics background and not a mathematician) is this limit impossible to evaulate ? and if so is it impossible because taking the limiting value of a dirac distribution doesn't make a whole lot of sense ?

Thanks
 
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  • #2
Sorry I mean to evaulate:
[tex]
\lim_{x\to 0^{+}} \frac{\delta'(x)}{\delta''(x)}
[/tex]
 
  • #3
Try writing the delta function as limit of a Gaussian, for example.
 
  • #4
Where did this limit come from? I don't believe it even makes sense...
 

1. What is a Dirac delta distribution?

A Dirac delta distribution, also known as a Dirac delta function, is a mathematical concept used to represent an infinitely narrow spike or impulse at a specific point in a function. It is often used in physics and engineering to model point sources or idealized point particles.

2. What is the limit involving a Dirac delta distribution?

The limit involving a Dirac delta distribution is a mathematical operation that involves taking the limit of a function as it approaches the location of the delta function. This can be written as ∫f(x)δ(x-a)dx, where δ(x-a) represents the Dirac delta distribution centered at a. The result of this limit is often related to the value of the function at the point a.

3. How is the limit involving a Dirac delta distribution calculated?

The limit involving a Dirac delta distribution is typically calculated using the properties of the delta function. For example, the integral of the delta function over its entire domain is equal to 1. This property can be used to simplify the limit expression and evaluate the result.

4. What are some applications of the limit involving Dirac delta distributions?

The limit involving Dirac delta distributions has many applications in physics and engineering. It is commonly used to solve differential equations, model point sources or particles, and describe impulse responses in systems. It is also used in signal processing and control theory.

5. Are there any limitations to using Dirac delta distributions in limits?

While Dirac delta distributions are a useful mathematical tool, they have some limitations. One of the main limitations is that they are not actual functions, but rather generalized functions or distributions. This means that they do not have a well-defined value at the point where they are centered, and they cannot be evaluated at that point. Additionally, some operations, such as differentiation and integration, may not be valid for delta functions.

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