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Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ $\{0,1\}$?

Note here $p$ and numerator and denominator of the rational function can be multiaffine.

What tools could be useful to study problems in case $1)$?

(Can the degree be $m^2$ for $p$ and $m$ for $f$? One possible candidate is here http://mathoverflow.net/questions/184635/composition-of-multilinear-forms-on-a-set-of-points)

Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ $\{0,1\}$?

Note here $p$ and numerator and denominator of the rational function can be multiaffine.

What tools could be useful to study problems in case $1)$?

(Can the degree be $m^2$ for $p$ and $m$ for $f$? One possible candidate is here https://mathoverflow.net/questions/184635/composition-of-multilinear-forms-on-a-set-of-points)

Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ $\{0,1\}$?

Note here $p$ and numerator and denominator of the rational function can be multilinear.

What tools could be useful to study problems in case $1,2,3$?

Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ $\{0,1\}$?

Note here $p$ and numerator and denominator of the rational function can be multiaffine.

What tools could be useful to study problems in case $1)$?

(Can the degree be $m^2$ for $p$ and $m$ for $f$? One possible candidate is here http://mathoverflow.net/questions/184635/composition-of-multilinear-forms-on-a-set-of-points)

Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ subset of primes

$2)$ subset of integers

$3)$ $\{0,1\}$?

What tools could be useful to study problems in case $1,2,3$?

Let $S$ be a collection of points on the real line.

Let $\{x_i\}_{i=1}^n$ take values in $S$.

Consider a polynomial $p(x_1,x_2,\dots,x_n)$ over $\mathbb R[x_1,x_2,\dots,x_n]$ of degree $d$ which when evaluated on $S$ takes values in $S$.

Can one say anything about the degree of smallest rational function (sum of degrees of numerator and denominator) over $\mathbb R(x_1,x_2,\dots,x_n)$ which when evaluated on $S$ takes identical values as that of $p(x_1,x_2,\dots,x_n)$ at least for special subsets of $S$ such as:

$1)$ $\{0,1\}$?

Note here $p$ and numerator and denominator of the rational function can be multilinear.

What tools could be useful to study problems in case $1,2,3$?