►Jacobian elliptic functions with real moduli in the intervals and , or with purelyimaginary moduli are related to functions with moduli in the interval by the following formulas.
…
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►Furthermore, for
and also have purelyimaginary zeros that correspond uniquely to the purelyimaginary
-zeros of (§10.21(i)), and they are asymptotically equal as and .
…
C. H. Ziener, M. Rückl, T. Kampf, W. R. Bauer, and H. P. Schlemmer (2012)Mathieu functions for purelyimaginary parameters.
J. Comput. Appl. Math.236 (17), pp. 4513–4524.
M. E. H. Ismail and M. E. Muldoon (1995)Bounds for the small real and purelyimaginary zeros of Bessel and related functions.
Methods Appl. Anal.2 (1), pp. 1–21.
T. M. Dunster (1990a)Bessel functions of purelyimaginary order, with an application to second-order linear differential equations having a large parameter.
SIAM J. Math. Anal.21 (4), pp. 995–1018.
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Notes:
Errata: In eq. (2.8) replace by .
In eq. (4.2) should be replaced by .
In the second line of eq. (4.7) insert an external factor
and change the upper limit of the sum
to .
In eq. (4.15) the factor is missing from the arguments
of the functions Biν and Bi’ν.
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►Its dynamics for purelyimaginary time is connected to the theory of instantons (Itzykson and Zuber (1980, p. 572), Schäfer and Shuryak (1998)), to WKB theory, and to large-order perturbation theory (Bender and Wu (1973), Simon (1982)).
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