# isolated essential singularity

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## 1—10 of 98 matching pages

##### 1: 1.10 Functions of a Complex Variable

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►Then $z={z}_{0}$ is an

*isolated singularity*of $f(z)$. …Lastly, if ${a}_{n}\ne 0$ for infinitely many negative $n$, then ${z}_{0}$ is an*isolated essential singularity*. … ► … ► … ►In any neighborhood of an isolated essential singularity, however small, an analytic function assumes every value in $\u2102$ with at most one exception. …##### 2: 32.2 Differential Equations

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►be a nonlinear second-order differential equation in which $F$ is a rational function of $w$ and $dw/dz$, and is

*locally analytic*in $z$, that is, analytic except for isolated singularities in $\u2102$. In general the singularities of the solutions are*movable*in the sense that their location depends on the constants of integration associated with the initial or boundary conditions. An equation is said to have the*Painlevé property*if all its solutions are free from*movable branch points*; the solutions may have movable poles or movable isolated essential singularities (§1.10(iii)), however. …##### 3: 1.18 Linear Second Order Differential Operators and Eigenfunction Expansions

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►Often circumstances allow rather stronger statements, such as uniform convergence, or pointwise convergence at points where $f(x)$ is continuous, with convergence to $(f({x}_{0}-)+f({x}_{0}+))/2$ if ${x}_{0}$ is an isolated point of discontinuity.
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►An essential feature of such symmetric operators is that their eigenvalues $\lambda $ are real, and eigenfunctions
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►In unusual cases $N=\mathrm{\infty}$, even for all $\mathrm{\ell}$, such as in the case of the

*Schrödinger–Coulomb problem*($V=-{r}^{-1}$) discussed in §18.39 and §33.14, where the point spectrum actually*accumulates*at the onset of the continuum at $\lambda =0$, implying an*essential singularity*, as well as a branch point, in matrix elements of the resolvent, (1.18.66). … ► …##### 4: 31.13 Asymptotic Approximations

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►For asymptotic approximations of the solutions of Heun’s equation (31.2.1) when two singularities are close together, see Lay and Slavyanov (1999).
►For asymptotic approximations of the solutions of confluent forms of Heun’s equation in the neighborhood of irregular singularities, see Komarov et al. (1976), Ronveaux (1995, Parts B,C,D,E), Bogush and Otchik (1997), Slavyanov and Veshev (1997), and Lay et al. (1998).

##### 5: 1.4 Calculus of One Variable

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►A

*removable singularity*of $f(x)$ at $x=c$ occurs when $f(c+)=f(c-)$ but $f(c)$ is undefined. … … ►Ismail (2005, p 5) refers to these ${x}_{n}$ as isolated atoms. …##### 6: 18.39 Applications in the Physical Sciences

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►The Schrödinger operator essential singularity, seen in the accumulation of discrete eigenvalues for the attractive Coulomb problem, is mirrored in the accumulation of jumps in the discrete Pollaczek–Stieltjes measure as $x\to -1-$.
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##### 7: 14.32 Methods of Computation

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►Essentially the same comments that are made in §15.19 concerning the computation of hypergeometric functions apply to the functions described in the present chapter.
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##### 8: 2.4 Contour Integrals

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►However, for the purpose of simply deriving the asymptotic expansions the use of steepest descent paths is not essential.
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►The problems sketched in §§2.3(v) and 2.4(v) involve only two of many possibilities for the coalescence of endpoints, saddle points, and singularities in integrals associated with the special functions.
…For a coalescing saddle point and endpoint see Olver (1997b, Chapter 9) and Wong (1989, Chapter 7); if the endpoint is an algebraic singularity then the uniform approximants are parabolic cylinder functions with fixed parameter, and if the endpoint is not a singularity then the uniform approximants are complementary error functions.
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►For two coalescing saddle points and an algebraic singularity see Temme (1986), Jin and Wong (1998).
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##### 9: Bibliography K

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Essential singularity of the Painlevé function of the second kind and the nonlinear Stokes phenomenon.
Zap. Nauchn. Sem. Leningrad. Otdel. Mat. Inst. Steklov.
(LOMI) 187, pp. 139–170 (Russian).
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Asymptotic approximations for the first incomplete elliptic integral near logarithmic singularity.
J. Comput. Appl. Math. 205 (1), pp. 186–206.
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##### 10: 18.40 Methods of Computation

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►This is a challenging case as the desired ${w}^{\mathrm{RCP}}(x)$ on $[-1,1]$ has an essential singularity at $x=-1$.
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