Andrei Kolmogorov developed in a 1931 paper a large part of the early theory of continuous-time Markov processes.   Kolmogorov was partly inspired by Louis Bachelier's 1900 work on fluctuations in the stock market as well as Norbert Wiener 's work on Einstein's model of Brownian movement.   He introduced and studied a particular set of Markov processes known as diffusion processes, where he derived a set of differential equations describing the processes.   Independent of Kolmgorov's work, Sydney Chapman derived in a 1928 paper an equation, now called the Chapman–Kolmogorov equation , in a less mathematically rigorous way than Kolmogorov, while studying Brownian movement.  The differential equations are now called the Kolmogorov equations  or the Kolmogorov–Chapman equations.  Other mathematicians who contributed significantly to the foundations of Markov processes include William Feller , starting in 1930s, and then later Eugene Dynkin , starting in the 1950s.