title: Riemann equation for prime number diffusion.
abstract: This study makes the first attempt to propose the Riemann diffusion equation to describe in a manner of partial differential equation and interpret in physics of diffusion the classical Riemann method for prime number distribution. The analytical solution of this equation is the well-known Riemann representation. The diffusion coefficient is dependent on natural number, a kind of position-dependent diffusivity diffusion. We find that the diffusion coefficient of the Riemann diffusion equation is nearly a straight line having a slope 0.99734 in the double-logarithmic axis. Consequently, an approximate solution of the Riemann diffusion equation is obtained, which agrees well with the Riemann representation in predicting the prime number distribution. Moreover, we interpret the scale-free property of prime number distribution via a power law function with 1.0169 the scale-free exponent in respect to logarithmic transform of the natural number, and then the fractal characteristic of prime number distribution is disclosed.
authors.affiliation: Institute of Soft Matter Mechanics, College of Mechanics and Materials, Hohai University, No. 1 XiKang Road, Nanjing, Jiangsu 210098, China.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
authors.affiliation: Institute of Soft Matter Mechanics, College of Mechanics and Materials, Hohai University, No. 1 XiKang Road, Nanjing, Jiangsu 210098, China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Liang