Integrating Complex Variables - Types & Solutions

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Discussion Overview

The discussion centers on the integration of complex variables, exploring different types of integrals involving complex numbers, and the methods for performing these integrations. Participants examine both theoretical and practical aspects of integrating functions over the complex plane.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that there are two types of integrals: one where the integrands involve complex numbers but the variable of integration is real, and another where both the integrands and the variable of integration are complex.
  • Others argue that the second type can be transformed into the first type by expressing the complex variable in terms of real variables, suggesting that this may complicate the integration process.
  • One participant questions how to integrate a complex function over the entire complex plane, considering whether to integrate along the real axis and then the imaginary axis, or to use a contour integral with a circular path extending to infinity.
  • Another participant suggests that using a contour integral over a circle with an infinite radius would be a more feasible approach than integrating along the axes.
  • There is a discussion about the relationship between real and complex numbers, with some participants noting that real numbers can be viewed as a subset of complex numbers.
  • One participant emphasizes the need to specify a path when integrating complex functions, as complex numbers correspond to points in a plane.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to integrating complex functions or the classification of integrals involving complex variables. Multiple competing views remain regarding the methods and interpretations of integration in this context.

Contextual Notes

Limitations include the lack of clarity on the assumptions regarding the paths of integration and the definitions of the types of integrals discussed. The discussion does not resolve the complexities involved in integrating over the entire complex plane.

BeauGeste
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I'm a little confused about integration with complex variables.
Are there two types of integrals?:
1. Integrands with complex numbers but the variable of integration is real.
2. Intregands with complex numbers and the variable of integration is also complex.
But can't (2.) be made into (1.) by dz = dx + i dy...you then have two integrations over real numbers...?
 
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real numbers are complex numbers.

integration is often done on a contour in the plane, one could parametrize this contour and use real integration like you suggested. It would prolly be tougher to do this tho.
 
how would you integrate a complex function over all space (whole complex plane)? integrate real axis -inf to +inf and then integrate imaginary axis -inf to +inf? Or do a contour integral where the contour is a circle and extend the radius to infinity?
 
I think that the first way would be more difficult if possible. You would just use a contour integral over a circle with a radius going to infinity.
 
SiddharthM: Real numbers are complex numbers.

This echoes my friend's engineering Prof. He explained to his Freshman class that Mathematicians made an unfortunate choice of words, and "Complex numbers are as real as real numbers."
 
The reals are a subset of the complex numbers is probably a better way to word it.
 
BeauGeste said:
how would you integrate a complex function over all space (whole complex plane)? integrate real axis -inf to +inf and then integrate imaginary axis -inf to +inf? Or do a contour integral where the contour is a circle and extend the radius to infinity?

When you are integrating real valued functions of real numbers you typically integrate from one number to another. Since complex numbers correspond to points in the PLANE, to do the equivalent you need to specify a path between the two points. If you really mean integrate over the entire complex plane, they you let z= x+ iy and do a double integral over x and y.
 

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