Ci field
= Ci field
{c}
{title2=$N>d^i$}
= Cr field
{c}
{synonym}
A field is $C_i$ if every <homogeneous polynomial> of degree $d\ge1$ in more than $d^i$ variables has a nonzero zero. Algebraically closed fields are $C_0$, <finite fields> are $C_1$, and the <Lang-Nagata theorem for Ci fields> controls function-<field extensions>.