C-R of Laurent Series

  • Context: Graduate 
  • Thread starter Thread starter hob
  • Start date Start date
  • Tags Tags
    Laurent series Series
Click For Summary

Discussion Overview

The discussion revolves around the methods of complex contour integration, specifically the use of the Cauchy-Riemann equations and Laurent series. Participants explore the criteria for selecting between these methods when evaluating integrals, particularly in relation to finding residues and coefficients in the context of complex analysis.

Discussion Character

  • Debate/contested

Main Points Raised

  • Hob questions the selection criteria for using the Cauchy-Riemann formula versus the Laurent series in complex contour integration.
  • One participant seeks clarification on the application of the Cauchy-Riemann equations in contour integration, specifically whether it involves direct integration or residue summation.
  • Another participant confirms that summing residues within the contour relates to the integral around the contour and mentions the use of Laurent expansion to find the first principal coefficient.
  • A later reply asserts that the first principal coefficient of the Laurent expansion corresponds to the residue at the pole, suggesting a connection between the two methods.
  • One participant proposes that the residue method is generally preferred over direct integration for evaluating integrals, implying that direct integration is more complex.

Areas of Agreement / Disagreement

Participants express differing views on the preferred methods for complex integration, with some advocating for the residue method while others question the clarity of the methods discussed. No consensus is reached on the selection criteria for these methods.

Contextual Notes

Participants do not clarify the specific conditions under which one method may be favored over the other, nor do they address potential limitations or assumptions inherent in their arguments.

hob
Messages
6
Reaction score
0
When doing complex contour integration one can use the C-R formula or the Laurent series and find the first coefficient of the principle part. What are the selection criteria for choosing these methods?

Regards,

Hob
 
Physics news on Phys.org
What do you mean by "use the Cauchy-Riemann equations to do a contour integral"? Are you referring to actually integrating around the contour as opposed to summing the residues inside the contour?
 
Hi, I mean summing within the contour.

[tex]2 \pi[/tex] x [tex]\sum residues[/tex] = Integral around the contour.

You can also use the Laurent Expansion and finding the first principle coefficient.

I am unsure what method you would use when presented with a complex integration,

Regards,
 
Last edited:
??The "first principle coefficient" of the Laurent expansion, around pole [itex]z_0[/itex], by which I think you mean the coefficient of [itex]z^{-1}[/itex], is the residue at that [itex]z_0[/itex]. They are the same method.
 
Correct me if I'm wrong, but I think you mean should you try to evaluate the integral directly, or do the residue by other means? Almost certainly the residue method. After all, if you could muscle your way through integrals, you wouldn't need contour integration.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
5K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 1 ·
Replies
1
Views
6K
  • · Replies 3 ·
Replies
3
Views
12K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 3 ·
Replies
3
Views
4K