Math 2.0

Special functions Definition

Complex power

Builds on Complex exponentialComplex logarithmPrincipal branch

Definition

Let z,w∈ℂz, w \in \mathbb{C} with z≠0z \neq 0. The complex powers of zz with exponent ww are the numbers ewℓe^{w \ell}, where ℓ\ell runs through the complex logarithms of zz. The principal value of zwz^w is zw=ewLog⁡z,z^w = e^{w \operatorname{Log} z}, where Log⁡\operatorname{Log} is the principal branch of the logarithm and eue^u is the complex exponential of uu.

Remarks

The powers of zz with exponent ww are the numbers ewLog⁡ze2πikwe^{w \operatorname{Log} z} e^{2 \pi i k w} with k∈ℤk \in \mathbb{Z}. There is one value if ww is an integer, there are qq values if w=p/qw = p/q in lowest terms with q≥2q \ge 2, and there are infinitely many values otherwise. For an integer w=nw = n, znz^n is the usual product of nn factors zz, or of −n-n factors 1/z1/z. For example, ii=ei⋅iπ/2=e−π/2i^i = e^{i \cdot i \pi/2} = e^{-\pi/2}, a positive real number. The usual rules can fail: with principal values, (za)b≠zab(z^a)^b \neq z^{ab} for some z,a,bz, a, b. A common convention for z=0z = 0 is 00=10^0 = 1 and 0w=00^w = 0 for w≠0w \neq 0.

Reading path

To understand this page from the ground up, read these 16 pages in order. The foundations come first.

Show the path as a graph
Each page uses the pages above it. The colour of the bar on a box shows how strong the evidence is, and the box also gives it as text. The list has the same pages.
  • no evidence level
  1. Complex numbers object
  2. Multivalued function concept
  3. Real numbers object
  4. Set bounded above definition
  5. Complex exponential definition
  6. Real and imaginary parts definition
  7. Supremum definition
  8. Completeness axiom statement
  9. Existence of square roots of nonnegative reals statement
  10. Square root definition
  11. Modulus of a complex number definition
  12. Argument of a complex number definition
  13. Complex logarithm definition
  14. Principal value of the argument statement
  15. Principal branch definition
  16. Complex power definition

Further reading

  1. Web https://en.wikipedia.org/wiki/Exponentiation, Complex exponentiation
  2. Web https://en.wikipedia.org/wiki/Exponentiation, Principal value
About this page
Tag0ZV9A7EV0F
URIm2://0ZV9A7EV0F
Kinddefinition
WritingW0 stub
MSC33B10
DefinesComplex power
UsesComplex exponential, Complex logarithm, Principal branch

Markdown · JSON · Edit on GitHub

What this page needs for W1

  • an inventory row: the row of the inventory that the node accounts for (0 of 1)

The writing levels say how complete the text of a page is. They do not measure its truth.

What links here

No page links to this page yet.