On the density function of the distribution of real algebraic numbers

In this paper we study the distribution of the real algebraic numbers. Given an interval $I$, a positive integer $n$ and $Q>1$, define the counting function $\Phi_n(Q;I)$ to be the number of algebraic numbers in $I$ of degree $n$ and height $\le Q$. Let $I_x = (-\infty,x]$. The distribution function is defined to be the limit (as $Q\to\infty$) of $\Phi_n(Q;I_x)$ divided by the total number of real algebraic numbers of degree $n$ and height $\le Q$. We prove that the distribution function exists and is continuously differentiable. We also give an explicit formula for its derivative (to be referred to as the distribution density) and establish an asymptotic formula for $\Phi_n(Q;I)$ with upper and lower estimates for the error term in the asymptotic. These estimates are shown to be exact for $n \ge 3$. One consequence of the main theorem is the fact that the distribution of real algebraic numbers of degree $n \ge 2$ is non-uniform.