Clarifications regarding definitions of Taylor, Laurent etc. series

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SUMMARY

The discussion clarifies the distinctions between Taylor series, Laurent series, and asymptotic series. The Taylor series is defined as f(0) + x.f'(0) + x².f''(0)/2!, applicable within a disk in the complex plane. The Laurent series, on the other hand, is used when the Taylor series cannot be applied, particularly when f(0) is undefined, and it converges on an annulus. Asymptotic series are specifically focused on behavior around infinity, confirming that each series serves unique purposes in complex analysis.

PREREQUISITES
  • Understanding of complex functions and holomorphicity
  • Familiarity with series expansions in calculus
  • Knowledge of convergence criteria in complex analysis
  • Basic principles of Taylor and Laurent series
NEXT STEPS
  • Study the properties of holomorphic functions in complex analysis
  • Learn about the convergence of series in the complex plane
  • Explore practical applications of Laurent series in residue theory
  • Investigate asymptotic analysis techniques and their applications
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Mathematicians, students of complex analysis, and anyone interested in advanced calculus and series expansions will benefit from this discussion.

Avichal
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I want to know the difference between various kinds of series like Taylor, Laurent and Asymptotic.

I have some understanding but I want some clarifications. Here is what I understand:-
1) Taylor series is just f(0) + x.f'(0) + x2.f''(0)/2! + ...
2) Laurent series is applied when taylor series cannot be applied like when f(0) is not defined.
3) Asymptotic series is around infinty point.

Am I correct? Correct me if I'm wrong
 
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Here are some crucial differences:
1. A Laurent series is convergent on an annulus in the complex plane, whereas the Taylor series is on a disk.

2. EVERY function that is holomorphic on r < | z - a | < R has a unique, convergent Laurent series (defined on this disk. The exact values of the coefficients depend on the annulus). This is a very strong claim, this is far from being true for a Taylor series. You might have R = infinity and r=0.

3. From a practical point of view: a Laurent series contains in general terms with negative powers, e.g. (z-a)^(-n) (when r > 0).
 
Here are some crucial differences:
1. A Laurent series is convergent on an annulus in the complex plane, whereas the Taylor series is on a disk.

2. EVERY function that is holomorphic on r < | z - a | < R has a unique, convergent Laurent series (defined on this disk. The exact values of the coefficients depend on the annulus). This is a very strong claim, this is far from being true for a Taylor series. You might have R = infinity and r=0.

3. From a practical point of view: a Laurent series contains in general terms with negative powers, e.g. (z-a)^(-n) (when r > 0).
 
Before that I have one more confusion. What does around a point mean when finding series of some function.
When finding taylor series, that means we use derivative at that point to approximate.

In case of laurent series, what does 'around some point' mean?
Also suppose I want a series expansion of e1/x what would I apply? Laurent or asymptotic?

Also am I write about asymptotic series i.e. it is series around point = infinity?
 

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