Conditional convergence
In mathematics, a series or integral is said to be conditionally convergent if it converges, but it does not converge absolutely.
Definition
More precisely, a series of real numbers is said to converge conditionally if exists (as a finite real number, i.e. not or ), but
A classic example is the alternating harmonic series given by which converges to , but is not absolutely convergent (see Harmonic series).
Bernhard Riemann proved that a conditionally convergent series may be rearranged to converge to any value at all, including ∞ or −∞; see Riemann series theorem. The Lévy–Steinitz theorem identifies the set of values to which a series of terms in Rn can converge.
A typical conditionally convergent integral is that on the non-negative real axis of (see Fresnel integral).
See also
- Absolute convergence
- Unconditional convergence
References
- Walter Rudin, Principles of Mathematical Analysis (McGraw-Hill: New York, 1964).
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