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Special functions, orthogonal polynomials, harmonic analysis, ordinary differential equations (ODE's), differential relations, calculus of variations, approximations, expansions, asymptotics.

0 votes

Is the following function decreasing on $(0,1)$?

This is more of a long comment to the remark in GH's answer. I did some calculations regarding the expression $$-\frac{q}{1-q} - \sum_{n=1}^{\infty} \frac{8nq^{4n}}{1-q^{4n}} + \sum_{n=1}^{\infty}\fra …
Malik Younsi's user avatar
  • 2,154
18 votes
4 answers
3k views

Is the following function decreasing on $(0,1)$?

Hi, I asked some time ago the following question on math.stackexchange, but I ask it here too since it remains unanswered. The question concerns a function I encountered during research : $$f(k):= …
Malik Younsi's user avatar
  • 2,154
1 vote
1 answer
142 views

On the geometry of roots of a sum of complex linear fractions

I was wondering if there is anything known about the geometry (position) of the roots of a rational map of the form $$R(z):= \sum_{j=1}^{n} \frac{a_j}{z-p_j},$$ where the $a_j$'s are nonzero complex n …
Malik Younsi's user avatar
  • 2,154
3 votes
2 answers
391 views

Is this infinite series related to some well-known special functions?

Please allow me to resort once again to the expertise of the MathOverflow community : During research I encoutered the following infinite series : $$\sum_{n=-\infty}^{+\infty} \frac{u^{2n}}{1+\rho^{ …
Malik Younsi's user avatar
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8 votes

Which sequences can be extended to analytic functions? (e. g., Ackermann's function)

Actually, there is an even stronger result, often called the interpolation theorem, which follows from a well-known theorem of Mittag-Leffler: Let $(z_n)$ be a sequence of complex numbers with no lim …
Malik Younsi's user avatar
  • 2,154
7 votes

Reference for complex analysis jargon

I really recommend the book Potential Theory in the complex plane" by Thomas Ransford. It's a very nice book with exercises and it covers each of the 5 points you mentioned.
Malik Younsi's user avatar
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