Bounding Analytic Functions by derivatives

In summary, the conversation discusses the existence of a function that is unbounded and analytic in a domain D, where its first derivative is bounded in D. The question is whether there exists such a function where all higher derivatives are also unbounded in D. It is determined that such a function does not exist, as a consequence of Cauchy Integral bounds. The conversation also clarifies that D must be an infinite domain and the function must be analytic in order for this scenario to occur.
  • #1
Hyperbolful
14
0
Ok my last post was trivial, but it led to this question

Assume f is unbounded and analytic in some domain D, and f' is bounded in D

does there exist a function for which the above holds and f'',f''',... are all unbounded in D?
 
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  • #2
D must be an infinite domain, else, if f was unbounded, f' would also be unbounded.

now, suppose that f'' is unbounded, that means that the area under it will grow unboundedly fast,
which implies that f' wil be unbounded

there is not such function
 
  • #3
By D infinite do you mean an unbounded domain? I'm referring to subsets of the complex plane.

So yes if f is analytic, then f' is analytic, and if f' is bounded on all of C then by louiville's theorem f' is constant so then the rest of the derivatives are zero and hence bounded.

Sorry, I meant my question to more complex analysis based. What it amounts to is a function unbounded on an unbounded subset of the complex plane, that isn't the whole plane, and who's derivative is bounded in the same domain, but who's other derivatives are all unbounded in that domain as well.

I think it still doesn't exist as a consequence of Cauchy Integral bounds though
 

FAQ: Bounding Analytic Functions by derivatives

What are bounding analytic functions by derivatives?

Bounding analytic functions by derivatives is a mathematical technique used to estimate the behavior of a complex-valued function, typically over a specific interval or region. This technique involves using the derivatives of the function to determine its maximum and minimum values within the given domain.

Why is it important to bound analytic functions by derivatives?

Bounding analytic functions by derivatives is important because it allows us to make accurate predictions about the behavior of a function without needing to evaluate it at every point. This can save time and computational resources, making it a useful tool in many scientific and engineering fields.

How do you bound analytic functions by derivatives?

The process of bounding analytic functions by derivatives involves finding the first and second derivatives of the function, and then using these derivatives to determine the maximum and minimum values over the given interval. This can be done using calculus techniques such as the first and second derivative tests.

What are the applications of bounding analytic functions by derivatives?

Bounding analytic functions by derivatives has many practical applications in fields such as physics, engineering, and economics. It can be used to optimize functions in mathematical modeling, estimate the behavior of physical systems, and predict trends in financial data.

Are there any limitations to bounding analytic functions by derivatives?

While bounding analytic functions by derivatives is a useful technique, it does have its limitations. It requires the function to be differentiable over the given interval, and it may not provide accurate results for functions with complex behavior or discontinuities. Additionally, the accuracy of the bounds depends on the accuracy of the derivatives used.

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