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Laurent Decomposition of Functions on an Annulus in Complex Analysis

This concept establishes that a function analytic on an annulus can be decomposed into a sum of two functions—one analytic on the inner disk, one analytic outside a smaller disk—via a contour-integration argument using the Cauchy integral formula, and uses this decomposition to derive the Laurent series: a doubly-infinite power series in (z − z₀) with both positive and negative exponents, whose coefficients are given by a Cauchy-type integral formula. It belongs to complex analysis, generalizing Taylor series expansion to functions with singularities, and sits within the theory of analytic functions on annular domains.