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  2. Laurent series - Wikipedia

    en.wikipedia.org/wiki/Laurent_series

    e −1/x 2 and its Laurent approximations (labeled) with the negative degree rising. The neighborhood around the zero singularity can never be approximated. e −1/x 2 and its Laurent approximations. As the negative degree of the Laurent series rises, it approaches the correct function.

  3. Residue (complex analysis) - Wikipedia

    en.wikipedia.org/wiki/Residue_(complex_analysis)

    Suppose a punctured disk D = {z : 0 < |z − c| < R} in the complex plane is given and f is a holomorphic function defined (at least) on D. The residue Res(f, c) of f at c is the coefficient a −1 of (z − c) −1 in the Laurent series expansion of f around c. Various methods exist for calculating this value, and the choice of which method to ...

  4. Function of several complex variables - Wikipedia

    en.wikipedia.org/wiki/Function_of_several...

    As in complex analysis of functions of one variable, which is the case n = 1, the functions studied are holomorphic or complex analytic so that, locally, they are power series in the variables z i. Equivalently, they are locally uniform limits of polynomials; or locally square-integrable solutions to the n-dimensional Cauchy–Riemann equations.

  5. Residue theorem - Wikipedia

    en.wikipedia.org/wiki/Residue_theorem

    Suppose a punctured disk D = {z : 0 < |z − c| < R} in the complex plane is given and f is a holomorphic function defined (at least) on D. The residue Res(f, c) of f at c is the coefficient a −1 of (z − c) −1 in the Laurent series expansion of f around c. Various methods exist for calculating this value, and the choice of which method to ...

  6. Zeros and poles - Wikipedia

    en.wikipedia.org/wiki/Zeros_and_poles

    Its zeros in the left halfplane are all the negative even integers, and the Riemann hypothesis is the conjecture that all other zeros are along Re(z) = 1/2. In a neighbourhood of a point z 0 , {\displaystyle z_{0},} a nonzero meromorphic function f is the sum of a Laurent series with at most finite principal part (the terms with negative index ...

  7. Principal part - Wikipedia

    en.wikipedia.org/wiki/Principal_part

    The principal part at = of a function = = ()is the portion of the Laurent series consisting of terms with negative degree. [1] That is, = is the principal part of at .If the Laurent series has an inner radius of convergence of , then () has an essential singularity at if and only if the principal part is an infinite sum.

  8. Isolated singularity - Wikipedia

    en.wikipedia.org/wiki/Isolated_singularity

    In complex analysis, a branch of mathematics, an isolated singularity is one that has no other singularities close to it. In other words, a complex number z 0 is an isolated singularity of a function f if there exists an open disk D centered at z 0 such that f is holomorphic on D \ {z 0}, that is, on the set obtained from D by taking z 0 out.

  9. Kronecker limit formula - Wikipedia

    en.wikipedia.org/wiki/Kronecker_limit_formula

    In mathematics, the classical Kronecker limit formula describes the constant term at s = 1 of a real analytic Eisenstein series (or Epstein zeta function) in terms of the Dedekind eta function. There are many generalizations of it to more complicated Eisenstein series. It is named for Leopold Kronecker.