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Supremum Limit


The supremum limit, also called the limit superior or upper limit, of a sequence of real numbers a_n, written limsup and pronounced 'lim-soup,' is the limit of

 A_n=sup_(k>=n)a_k

as n->infty, where sup_(x in S)x denotes the supremum. Note that, by definition, A_n is nonincreasing and so has a limit in the extended real numbers, possibly -infty or +infty. For example, suppose a_n=(-1)^n/n, then for n odd, A_n=1/(n+1), and for n even, A_n=1/n. Another example is a_n=sinn, in which case A_n is a constant sequence A_n=1.

When limsupa_n=liminfa_n is finite, the sequence converges to that real number

 lima_n=limsupa_n=liminfa_n.

If the two values differ, the sequence does not converge even in the extended real numbers. If they agree at +infty or -infty, it converges only in the extended-real sense.


See also

Infimum Limit, Limit, Supremum, Upper Limit

Portions of this entry contributed by Todd Rowland

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Cite this as:

Weisstein, Eric W., with contributions by Todd Rowland. "Supremum Limit." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/SupremumLimit.html

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