Almost Unit
An almost unit is a nonunit in the integral domain of formal power series with a nonzero first coefficient, P=a_1x+a_2x^2+..., where a_1!=0. Under the operation of composition, the almost units in the integral domain of formal power series over a field F form a group (Henrici 1988, p. 45).
See also
Schur-Jabotinsky TheoremExplore with Wolfram|Alpha
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References
Henrici, P. Applied and Computational Complex Analysis, Vol. 1: Power Series-Integration-Conformal Mapping-Location of Zeros. New York: Wiley, p. 45, 1988.Referenced on Wolfram|Alpha
Almost UnitCite this as:
Weisstein, Eric W. "Almost Unit." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/AlmostUnit.html