Description of Instant Diffusion Equation of Price Changing and Time-Space Exchanging Description

Analogy to heat diffusion equation, an instant diffusion equation of price changing is obtained and
explained by “time-space exchange” via Newton’s second law, in which the partial derivative of price
respected to time is viewed as a “force”, and the derivative of transportation velocity of price between
commodities is viewed as an “acceleration”. It is a partial differential equation of second order. The
solution of this equation is found and the definitions of “order of commodities”, “distance between
commodities” are given. An important relationship of “time-space exchange” in a stationary process of
diffusion of price changing is found. This provides a base for describing the relation of “time-space
exchange” quantitatively. Examples for calculating and checking the diffusion of price changing in
pork, beef, and mutton based on the data taken on February 5th 2008 are given.