Math 2.0

Sequences, series, summability Definition

Absolute convergence

Builds on SeriesConvergent series

Definition

Let (an)(a_n) be a real sequence. The series ∑an\sum a_n converges absolutely if the series ∑∣an∣\sum |a_n| of absolute values converges.

Remarks

The series ∑∣an∣\sum |a_n| has nonnegative terms. So it converges exactly when its partial sums are bounded. Absolutely convergent series converge, but the converse fails. The alternating harmonic series converges, but not absolutely. A convergent series that does not converge absolutely is conditionally convergent. The same definition works for complex terms, with the modulus in place of the absolute value.

Reading path

To understand this page from the ground up, read these 8 pages in order. The foundations come first.

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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. Sequence definition
  2. Real sequence definition
  3. Limit of a sequence definition
  4. Series definition
  5. Convergent sequence definition
  6. Partial sum definition
  7. Convergent series definition
  8. Absolute convergence definition

Where this leads

117 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Absolute_convergence, Definition for real and complex numbers
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