Tchebyshev system
https://en.wikipedia.org/wiki/Chebyshev_polynomials#:~:text=[edit]-,Recurrence definition,-[edit]
$$ T_0(x)=1,T_1(x)=x \text{ or } 2x\\T_{n+1}(x)=2xT_n(x)-T_{n-1}(x),\ \forall n\geq 1 $$
至少$n-1$个分离零点distinct zeros
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commuting polynomials
$$ \begin{cases} \deg F_n(x)=n,\\ F_n\left(F_m(x)\right)=F_m\left(F_n(x)\right) \end{cases} $$
$\deg$ 是多项式的最高次项次数，$F_n(x)$的系数在一个特征为0（Characteristic 重复加至零的最小次数，$p\cdot a=\sum_{i=1}^pa=0\forall a\in \mathbb F$）的域上
$$ F_n(x)=\begin{cases} x^n\\\text{or}\\ 2T_n(\frac{x}{2}) \end{cases} $$
moment cone 矩量锥
$$ \mathcal S_A=\left\{\int a_id\mu < \infty\right\} $$
measurable functions $A=\{a_i\}^m$on a measurable space $(\mathcal X,\mathcal U)$
$\mu$ is a positive measure on $(\mathcal X,\mathcal U)$
https://arxiv.org/abs/1809.00584
Dio和Schmüdgen - 2018 - The multidimensional truncated Moment Problem The Moment Cone.pdf
