complex-analysis/ForStudents/листки Забродина/listok14.tex

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\documentclass[11pt,a4paper]{article}
\usepackage[cp1251]{inputenc}
\usepackage[russian]{babel}
\usepackage{amssymb,amsfonts,amsmath}
\usepackage{xspace}
\pagestyle{empty}
\newcounter{zadacha}
\setcounter{zadacha}0
\newcommand*{\nz}{%
\par\medskip\refstepcounter{zadacha}
\textbf{\thezadacha.} }
\let\C\relax
\newcommand*{\C}{\ensuremath{\mathbb C}\xspace}
\newcommand*{\R}{\ensuremath{\mathbb R}\xspace}
\newcommand*{\Z}{\ensuremath{\mathbb Z}\xspace}
\let\Re\relax
\let\Im\relax
\DeclareMathOperator{\Re}{Re}
\DeclareMathOperator{\Im}{Im}
\begin{document}
\begin{center}\large\sc
Òåîðèÿ ôóíêöèé êîìïëåêñíîãî ïåðåìåííîãî 2025\\ Ëèñòîê 14
\end{center}
\noindent
$\wp$-ôóíêöèÿ Âåéåðøòðàññà ñ ïåðèîäàìè $2\omega_1,
2\omega_2$ (${\rm Im}\, \omega_2/ \omega_1 >0$):
$$
\wp (z)=\frac{1}{z^2}+\sum_{s\neq 0} \Bigl (\frac{1}{(z-s)^2}-
\frac{1}{s^2}\Bigr ),
\quad s=2\omega_1 n_1 +2 \omega_2 n_2, \quad n_{1,2}\in \Z .
$$
Ðàçëîæåíèå â îêðåñòíîñòè $z=0$:
$$
\wp (z)=\frac{1}{z^2}+\frac{g_2}{20}\, z^2 +\frac{g_3}{28}\, z^4+O(z^6),
$$
$$
g_2=60\sum_{s\neq 0} s^{-4}, \quad g_3=140\sum_{s\neq 0} s^{-6}.
$$
$\zeta$- è $\sigma$-ôóíêöèè Âåéåðøòðàññà: $\zeta '(z)=-\wp (z)$, $\sigma '(z)/\sigma (z)=
\zeta (z)$,
$$
\zeta (z)=\frac{1}{z}-\int_{0}^{z}\Bigl (\wp (x)-\frac{1}{x^2}\Bigr )dx,
\quad
\log (\sigma (z)/z)=\int_{0}^{z}\Bigl (\zeta (x)-\frac{1}{x}\Bigr )dx.
$$
$$
\zeta (z)=\frac{1}{z}+\sum_{s\neq 0} \Bigl (\frac{1}{z-s}+\frac{1}{s}+\frac{z}{s^2}\Bigr ),
\quad
\sigma (z)=z\prod_{s\neq 0} \Bigl (1-\frac{z}{s}\Bigr )e^{\frac{z}{s}+\frac{z^2}{2s^2}}.
$$
$\zeta (z+2\omega_{\alpha} )=\zeta (z)+2\eta_{\alpha}$,
$\sigma (z+2\omega_{\alpha})=-e^{2\eta_{\alpha}(z+\omega_{\alpha})}
\sigma (z)$,
$\eta_{\alpha}=\zeta (\omega_{\alpha})$.
\noindent
Âûðàæåíèå $\sigma$-ôóíêöèè ÷åðåç òýòà-ôóíêöèþ:
$$
\sigma (z)=2\omega_1 e^{\eta_1 z^2/(2\omega_1 )}\frac{\theta_1(z/(2\omega_1 ))}{\theta_1'(0)}.
$$
\noindent
Ôóíêöèè ${\rm sn}$, ${\rm cn}$ è ${\rm dn}$:
$$
{\rm sn}\, u = \frac{\theta_3(0)}{\theta_2(0)}\,
\frac{\theta_1 \Bigl (\frac{u}{\pi \theta_3^2(0)}
\Bigr )}{\theta_4 \Bigl (\frac{u}{\pi \theta_3^2(0)}\Bigr )},
\;
{\rm cn}\, u = \frac{\theta_4(0)}{\theta_2(0)}\,
\frac{\theta_2 \Bigl (\frac{u}{\pi \theta_3^2(0)}
\Bigr )}{\theta_4 \Bigl (\frac{u}{\pi \theta_3^2(0)}\Bigr )},
\;
{\rm dn}\, u = \frac{\theta_4(0)}{\theta_3(0)}\,
\frac{\theta_3 \Bigl (\frac{u}{\pi \theta_3^2(0)}
\Bigr )}{\theta_4 \Bigl (\frac{u}{\pi \theta_3^2(0)}\Bigr )}.
$$
\nz
Äîêàæèòå, ÷òî ôóíêöèÿ $\wp (z)$ óäîâëåòâîðÿåò äèôôåðåíöèàëüíîìó óðàâíåíèþ
$$
(\wp '(z))^2 =4\wp ^3(z)-g_2\wp (z)-g_3.
$$
\nz
Äîêàæèòå òîæäåñòâî
$
\wp '''(z)=12\wp (z)\wp '(z).
$
\nz
Äîêàæèòå ñîîòíîøåíèå $2\eta_1 \omega_2 -2\eta_2 \omega_1 =\pi i$.
%\nz
%Äîêàæèòå òîæäåñòâî
%$$
%\wp (z+y)-\wp (z-y)=-\frac{\wp '(z)\wp '(y)}{(\wp (z)-\wp (y))^2}.
%$$
\nz
Äîêàæèòå, ÷òî ïðè $x+y+z=0$ ñïðàâåäëèâî òîæäåñòâî
$$
\left | \begin{array}{lll}
1 & \wp (x) & \wp '(x)
\\
1 & \wp (y) & \wp '(y)
\\
1 & \wp (z) & \wp '(z)
\end{array}
\right |=0.
$$
\nz
Âûðàçèòå
$\displaystyle{
\left | \begin{array}{lll}
1 & \wp (x) & \wp '(x)
\\
1 & \wp (y) & \wp '(y)
\\
1 & \wp (z) & \wp '(z)
\end{array}
\right |}
$
ïðè ïðîèçâîëüíûõ $x,y,z \in \C$ ÷åðåç $\sigma$-ôóíêöèè.
\nz
Äîêàæèòå, ÷òî ïðè $x+y+z=0$ ñïðàâåäëèâî òîæäåñòâî
$$
\Bigl (\zeta (x)+\zeta (y) +\zeta (z)\Bigr )^2=
\wp (x)+\wp (y)+\wp (z).
$$
\nz
Äîêàæèòå òîæäåñòâî
$$
\zeta (x-a_1)-\zeta (x-a_2)+\zeta (a_1-a_2)=-\frac{1}{2}\,
\frac{\wp '(x-a_1)+\wp '(x-a_2)}{\wp (x-a_1)-\wp (x-a_2)}.
$$
\nz
Äîêàæèòå òîæäåñòâà
$$
{\rm sn}^2\, u +{\rm cn}^2\, u =1, \quad
k^2{\rm sn}^2\, u +{\rm dn}^2\, u =1,
$$
ãäå $k^2=\theta_2^4(0)/\theta_3^4(0)$.
\end{document}