\begin{align*} &f(x)=3x^3+3x+1 \quad \{\alpha,\beta,\gamma\}: \ roots \ of \ f(x)\\ &Primitive \ element \quad v=1\cdot\alpha+2\cdot \beta+3\cdot\gamma \end{align*}
\begin{align*} v_{1}=\alpha+2\beta+3\gamma \qquad v_{2}=\alpha+2\gamma+3\beta \\ v_{3}=\beta+2\alpha+3\gamma \qquad v_{4}=\beta+2\gamma+3\alpha\\ v_{5}=\gamma+2\alpha+3\beta \qquad v_{6}=\gamma+2\beta+3\alpha \end{align*} \begin{align*} V(x)=&(x-v_{1})(x-v_{2})(x-v_{3})\\ \times&(x-v_{4})(x-v_{5})(x-v_{6}) \end{align*}
\[V(x, \ \alpha,\beta,\gamma): symmetric \ function \ in \{\alpha,\beta,\gamma\} \] \[\qquad \qquad \Downarrow\] \[V(x, \ e_{1},e_{2},e_{3})\] \[\{e_1,e_2,e_3\}: elementary \ symmetric \ functions\]
\[g_{0}(x)=x^6+18x^4+81x^2+135 \]
\[ \qquad g_0(x):minimal \ polynomial \ of \ v \ on \ F_0=Q(\omega) \]
\begin{align*} P_{\alpha}(x)=V(x)&\cdot \big( \frac{\gamma }{x-{v_6}}+\frac{\gamma }{x-{v_5}}+\frac{\beta }{x-{v_4}}\\ &+\frac{\beta }{x-{v_3}}+\frac{\alpha }{x-{v_2}}+\frac{\alpha }{x-{v_1}}\big)\\ \end{align*} \[\alpha=\left.\frac{P_\alpha(x)}{V'(x)}\right|_{x=v} \quad The \ same \ holds \ for \ \beta\ and \ \gamma \]
\begin{eqnarray*} \left\{ \begin{array}{l} \alpha&=\frac{{{v}^{4}}+15 {{v}^{2}}-9 v+36}{18}\\ \beta&=-\frac{{{v}^{4}}+15 {{v}^{2}}+36}{9}\\ \gamma&=\frac{{{v}^{4}}+15 {{v}^{2}}+9 v+36}{18}\\ \end{array} \right. \end{eqnarray*}
\begin{align*} v_{1}&=v & v_{2}&=\frac{-v^4}{6}-\frac{5v^2}{2}+\frac{v}{2}-6\\ v_{3}&=\frac{v^4}{6}+\frac{5v^2}{2}+\frac{v}{2}+6 & v_{4}&=\frac{v^4}{6}+\frac{5v^2}{2}-\frac{v}{2}+6\\ v_{5}&=-\frac{v^4}{6}-\frac{5v^2}{2}-\frac{v}{2}-6 & v_{6}&=-v \end{align*}
\begin{align*} &g_0(v_i)=0 \quad for \ (i=1,2,..,6) \\ &\qquad \qquad \Downarrow\ \\ &S_3: Galois \ group \ of \ f(x) \\ &\qquad composition \ series \ S_3 \rhd A_3 \rhd \{e\} \end{align*}
\[ g_{1}(x)=x^3+9x+a_{1} \in F_{1}[x] \]
\[\quad g_1(x):minimal \ polynomial \ of \ v \ on \ F_1=F_0(a_1)\\ \quad Here \ \ B_1=a_{1}^2 +135=0 \]
\[g_{2}(x)=x+{{a}_{2}^{2}}\, \left( -\frac{\omega }{3}+\frac{{a_1}}{18}-\frac{1}{6}\right) +{a_2} \in F_{2}[x]\]
\[ \quad g_2(x):minimal \ polynomial \ of \ v \ on \ F_2=F_0(a_1,a_2)\\ \quad Here \quad B_2=a_2^3-\frac{6 \omega +{a_1}+3}{2}=0, \ \Omega=\omega^2+\omega+1=0 \]
\begin{align*} v=&\frac{{{a}_{2}^{2}} \omega }{3}-\frac{{a_1} {{a}_{2}^{2}}}{18}+\frac{{{a}_{2}^{2}}}{6}-{a_2} \\ \\ \alpha=&-\frac{{a_1} \left( {{a}_{2}^{2}} \omega -{{a}_{2}^{2}}\right) +\left( 9 {{a}_{2}^{2}}-18 {a_2}\right) \omega +9 {{a}_{2}^{2}}-36 {a_2}}{54}\\ \beta=&\frac{{a_1} \left( 2 {{a}_{2}^{2}} \omega +{{a}_{2}^{2}}\right) -36 {a_2} \omega +9 {{a}_{2}^{2}}-18 {a_2}}{54}\\ \gamma=&-\frac{{a_1} \left( {{a}_{2}^{2}} \omega +2 {{a}_{2}^{2}}\right) +\left( -9 {{a}_{2}^{2}}-18 {a_2}\right) \omega +18 {a_2}}{54}\\ \\ Here &\quad B_1=a_{1}^2 +135=0,\\ &B_2=a_2^3-\frac{6 \omega +{a_1}+3}{2}=0, \\ &\Omega=\omega^2+\omega+1=0 \end{align*}
(覚書:冪根の実態は?)
\begin{align} \setCounter{33} \alpha&=\frac{18v^4-9v^3+162v^2-81v+405}{6v^5+72v^3+162v} \\ \end{align}
\begin{align} &\Bigl[ \frac{2 {{x}^{5}}+30 {{x}^{3}}+63 x}{7290} \Bigr] \cdot V'(x)+ \Bigl[ \frac{-2 {{x}^{4}}-18 {{x}^{2}}+9}{1215} \Bigr] \cdot g_0(x)=1\\ \notag \\ & \qquad \Downarrow \ substitute \ v \ for \ x \quad \rightarrow \quad g_0(v)=0 \notag \\ \notag \\ &\therefore \quad \Bigl[ \frac{2 {{v}^{5}}+30 {{v}^{3}}+63 v}{7290} \Bigr] \cdot V'(v)=1 \\ \notag \\ & \therefore \quad V'(v)^{-1}=\frac{2 {{v}^{5}}+30 {{v}^{3}}+63 v}{7290}=\frac{{{v}^{5}}}{3645}+\frac{{{v}^{3}}}{243}+\frac{7 v}{810}\\ \end{align}
\begin{align} V(v)'^{-1} \equiv IdV(v) \quad \Rightarrow IdV(v) \cdot V(v)'=1 \\ \end{align}
\begin{align} &IdV(v)= \quad c_5 \cdot v^5+c_4 \cdot v^4+c_3 \cdot v^3+c_2 \cdot v^2+c_1 \cdot v+c_0\\ &V(v)'= \quad 6v^5+72v^3+162v\\ \end{align}
\begin{align} \notag \\ &\therefore \ IdV(v) \cdot V(v)'\notag \\ &= \ 6c_5v^{10}+6c_4v^9+(72c_5+6c_3)v^8+(72c_4+6c_2)v^7 \notag \\ &+(162c_5+72c_3+6c_1)v^6+(162c_4+72c_2+6c_0)v^5 \notag \\ &+(162c_3+72c_1)v^4+(162c_2+72c_0)v^3+162c_1v^2 +162c_0v\\ \notag \\ &\qquad \Downarrow \quad g_0(v)で剰余する \notag \\ \notag \\ &= \quad (324c_4-36c_2+6c_0)v^5 +(-3726c_5+324c_3-36c_1)v^4 \notag\\ &+(2106c_4-324c_2+72c_0)v^3 +(-21384c_5+2106c_3-324c_1)v^2 \notag \\ &+(4860c_4-810c_2+162c_0)v -43740c_5+4860c_3-810c_1\\ &= \ 1 \\ \end{align}
\begin{align} &\left\{ \begin{array}{l} &(324c_4-36c_2+6c_0)=0 & &(-3726c_5+324c_3-36_c1)=0 \notag \\ &(2106c_4-324c_2+72c_0)=0 & &(-21384c_5+2106c_3-324c_1)=0 \\ &(4860c_4-810c_2+162c_0)=0 & &(-43740c_5+4860c_3-810c_1)=1 \\ \end{array} \right. \\ \end{align}
\begin{align} \Bigl[\ & c_0=0, \ c_1=\frac{7}{810}, \ c_2=0, \ c_3=\frac{1}{243}, \ c_4=0, \ c_5=\frac{1}{3645} \ \Bigr]\\ &\therefore \quad IdV(v)= V'(v)^{-1}= \frac{{{v}^{5}}}{3645}+\frac{{{v}^{3}}}{243}+\frac{7 v}{810} \\ \end{align}
\begin{align} \alpha&=\left.\frac{P_\alpha(x)}{V'(x)}\right|_{x=v} =\left.P_\alpha(x) \cdot IdV(x)\right|_{x=v} \notag \\ &=(18v^4-9v^3+162v^2-81v+405)\cdot\Bigl( \frac{2 {{v}^{5}}+30 {{v}^{3}}+63 v}{7290} \Bigr) \notag \\ &=\frac{v^4+15v^2-9v+36}{18} \qquad ( g_0(v)で剰余する)\\ \notag \\ \beta&=\left.P_\beta(x) \cdot IdV(x)\right|_{x=v}=-\frac{{{v}^{4}}+15 {{v}^{2}}+36}{9}\\ \gamma&=\left.P_\gamma(x) \cdot IdV(x)\right|_{x=v} =\frac{{{v}^{4}}+15 {{v}^{2}}+9 v+36}{18}\\ \end{align}
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1st upload: 2023/06/17
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